Tag Archives: masonry

Critical Bonds

slaton patterson sutterlinFAILURES
Deborah Slaton, David S. Patterson, AIA, and Jeffrey N. Sutterlin, PE

In the southeastern United States, a 12-story office building, constructed in the early 1930s, experienced uncontrolled water leakage through its mass masonry exterior wall. As this was attributed to weathering of the existing mortar joints in the brick and terra cotta façade, the joints were specified to be repointed with a 1:1:6 mortar mix (Type N per ASTM C270, Standard Specification for Mortar for Unit Masonry). The work was performed during the summer.

Example of water-damaged plaster finish on interior of recently pointed masonry wall. Photos courtesy David S. Patterson

Example of water-damaged plaster finish on interior of recently pointed masonry wall. Photos courtesy David S. Patterson

To match the original joint profile and aesthetic, the relatively wide (25-mm [1-in.]) mortar joints were struck flush with the brick face. Soon after repointing, water damage to the interior plaster wall finish was observed in localized areas adjacent the existing steel-framed punched windows. Leakage (and subsequent plaster damage) occurred primarily on the building’s north elevation, which is vulnerable to wind-driven rain. While diagnostic water testing of the window system did not result in leakage to the building interior, testing of the repointed masonry wall did.

Close-up examination of the exterior masonry revealed widespread bond line separations at the interface of the mortar and adjacent masonry in the vicinity of the interior water damage. Although many of these separations were very narrow (hairline), some were wider than 0.51 mm (0.02 in.). Even minor bond separations can represent potential leak sources—water can pass through gaps as narrow as 0.3 mm (0.012 in.).

Mortar-bond-line separations in exterior masonry are of particular concern in mass walls due to the network of inherent voids in the back-up masonry, which is typically in contact with the exterior assembly. During testing, water entered the exterior wall construction through mortar-bond-line separations and traveled inboard via voids in the terra cotta tile and brick backup wall, wetting its interior surface to which the plaster finish was applied.

Example of mortar-bond-line separation—the area of missing mortar was a unique condition. The dark-gray mortar on the face of the brick remains from an earlier repair campaign using face grouting (shell pointing). The irregular surface of the face of the brick also made tooling the repointing mortar more challenging.

Example of mortar-bond-line separation—the area of missing mortar was a unique condition. The dark-gray mortar on the face of the brick remains from an earlier repair campaign using face grouting (shell pointing). The irregular surface of the face of the brick also made tooling the repointing mortar more challenging.

While many factors can affect mortar bond, in this example installation and curing during hot weather without following proper procedures likely contributed to lower mortar bond strength and increased drying shrinkage, and thus to bond separations. American Concrete Institute (ACI) 530/530.1, Building Code Requirements and Specification for Masonry Structures, a joint publication with the Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE), and The Masonry Society (TMS), provides code requirements and specifications for hot weather practices for masonry construction, and is referenced in the International Building Code (IBC). A concise summary of the mandatory code practices required by IBC and ACI 530 with additional commentary is also provided in the Brick Industry Association (BIA) Technical Note 1, Cold and Hot Weather Construction, which serves as a good refresher for specifiers.

Water leakage at the interior face of the backup wall during testing of areas exhibiting mortar-bond-line separations.

Water leakage at the interior face of the backup wall during testing of areas exhibiting mortar-bond-line separations.

The opinions expressed in Failures are based on the authors’ experiences and do not necessarily reflect those of the CSI or The Construction Specifier.

Deborah Slaton is an architectural conservator and principal with Wiss, Janney, Elstner Associates, Inc. (WJE) in Northbrook, Illinois, specializing in historic preservation and materials conservation. She can be reached at dslaton@wje.com.
David S. Patterson, AIA, is an architect and senior principal with WJE’s Princeton, New Jersey, office, specializing in investigation and repair of the building envelope. He can be e-mailed at dpatterson@wje.com.
Jeffrey N. Sutterlin is an architectural engineer and senior associate with WJE’s Princeton office, specializing in investigation and repair of the building envelope. He can be contacted via e-mail at jsutterlin@wje.com.

Energy-efficient Design with Masonry Construction

Photo courtesy Richard Filloramo

Photo courtesy Richard Filloramo

by Richard Filloramo, B.S. Arch, A.S. CT, and Chris Bupp

Masonry materials and wall assemblies, with their inherent thermal mass characteristics, provide designers with many options to achieve efficient designs. Architects and engineers have to make new decisions to reduce their projects’ energy consumption, requiring close collaboration and coordination with building and energy codes, along with construction documents.

The most significant code changes include increased R-values for non-mass opaque walls (e.g. cold-formed metal framing), requirement options for continuous insulation (ci), a need for continuous air barriers, R-value reductions for thermal bridging, and three paths for building energy design.

The 2015 International Building Code (IBC), in Chapter 13 (“Energy Efficiency”) states buildings shall be designed in accordance with the 2015 International Energy Conservation Code (IECC). The latter code’s Chapter 5 (“Commercial Energy Efficiency”) enables designers to use either IECC or American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2013, Energy Standards for Buildings except Low-Rise Residential Buildings.

This article examines examples of energy design using ASHRAE 90.1-2013, Section 5 (“Building Envelope”), and also notes requirements from ASHRAE 90.1-2010 (per the 2012 IBC and IECC). Designers may select ASHRAE 90.1 over IECC Chapter 5 because it provides a more in-depth, comprehensive, and complete approach to building energy design.

First, a designer must determine the climate zone for the building location by using the ASHRAE appendix Figure B1-1 map and tables depicted in Figure 1. For example, all of Connecticut is in Climate Zone 5, while New York encompasses three Climate Zones—Table B1-1 indicates the appropriate zone for the various towns, cities, and counties.

Next, the architect will select a compliance path based on the climate zone, space conditioning category (ASHRAE 5.1.2) and class of construction from ASHRAE Section 5.2 (“Compliance Paths”), as shown in Figure 2. The building envelope must comply with Sections 5.1, 5.4, 5.7, and 5.8, along with either:

● Section 5.5 (“Prescriptive Building Design Option”), provided the fenestration area does not exceed the maximum allowed in Section 5.5.4.2 (40 percent in ASHRAE 2012); or
● Section 5.6 (“Building Envelope Trade-off Option”).

Projects may also use Energy Cost Budget Methods, Section 11, as described in ASHRAE 90.1, Section 5.2.2. This article focuses on the first option—the prescriptive path (Section 5.5)—and also discuss Section 5.4.3 (“Air Leakage and Continuous Air Barrier Requirements”).

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The prescriptive path
While larger commercial, institutional, and municipal buildings may use some form of energy modeling (Section 5.6 or Section 11), the examples shown using the prescriptive path demonstrate basic compliance with the code and assist at understanding assembly R-values for various building envelope wall systems. The prescriptive path method provides an efficient means to establish the required insulation in a wall that can be used in a final design or in a preliminary study.

ASHRAE 90.1, Section 5.5 provides building envelope design tables for all climate zones for either non-residential or residential construction. (The latter includes dwelling units, hotel/motel guest rooms, dormitories, nursing homes, patient rooms in hospitals, lodging houses, fraternity/sorority houses, hostels, prisons, and fire stations.1)

To comply with the prescriptive path for Opaque Areas (Section 5.5.3) a designer may select from one of the two following methods:

● Method A: minimum R-value insulation requirements; or
● Method B: maximum U-factor (or R-value) for the entire assembly (Figure 3).

The second method is a more efficient means to configure a masonry wall assembly.

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Building envelope basics
An essential component of wall design—masonry or otherwise—is drainage capability and ventilation air space. IBC Chapter 14 (“Exterior Walls”) requires the exterior wall envelope be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer, and a means for draining water that enters the assembly to the exterior. While there are exceptions, this requirement is essential to successful design.

Ventilated air space is also essential to keep the wall components dry, which prevents deterioration of wall components and water infiltration. Providing a sufficient air space in accordance with industry standards has become more difficult as new energy requirements can increase insulation thickness—owners are apprehensive to allow thicker walls that will encroach on the net interior building area.

The 2015 IBC references the Masonry Standards Joint Committee (MSJC)’s Building Code Requirements for Masonry Structures (i.e. The Masonry Society [TMS] 402-13/American Concrete Institute [ACI] 530-13/American Society of Civil Engineers [ASCE] 5-13) and Specifications for Masonry Structures (TMS 602-13/ACI 530.1-13/ASCE 6-13). In Chapter 12 (“Veneers”), Sections 12.2.2.6.2, 12.2.2.7.4, 12.2.2.8.2, and 6.2.2.8 states:

A 1-in. (25.4 mm) minimum air space shall be specified.

However, this is a code minimum and not recommended. Standard construction tolerance for the veneer and backup of ± 6 mm (¼ in.) variation from plumb can leave a resulting 12-mm (½-in.) air space, which is unacceptable. Industry organizations such as the International Masonry Institute (IMI), Brick Industry Association (BIA), and National Concrete Masonry Association (NCMA) recommend a 50-mm (2-in.) minimum air space. With these new increased requirements for higher R-values and sometimes thicker insulation, a 38-mm (1 ½-in.) air space would be sufficient. If air spaces are smaller, it may be advisable to provide continuous, full-height drainage mat in the wall cavity to assist with drainage and air flow and prevent mortar bridging (Figure 4).

It should also be noted MSJC sets the maximum cavity space at 114 mm (4 ½ in.) based on prescriptive design. Cavity spaces exceeding this size are acceptable, provided engineering calculations are provided for the masonry veneer ties. Recently, newer and stronger masonry ties, anchors, and fasteners have been developed that provide sufficient strength for wider cavities.

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Understanding the prescriptive path
An example of ASHRAE Table 5.5.5 for Building Envelope requirements in Zone 5 is shown in Figure 5. A masonry mass wall (masonry veneer and concrete masonry unit [CMU] backup), non-residential, under Method B (first column), would require an assembly U-factor of U-0.090—this equals R- 11.11(R=1/U). It should be noted there was no increase in the required R-value for mass walls from the R-11.11 in 2012 IBC/IECC/ ASHRAE 2010).

The same mass wall under Method A (second column) would require continuous insulation with a minimum R-value of R-11.4. A steel-framed wall (masonry veneer and steel stud backup) under Method B requires an assembly U-factor of U-0.055—this equals R-18.18. It should be noted this is a significant increase from R-15.63 required in the 2012 IBC/IECC/ASHRAE 2010). The same stud wall under Method A would require R-13 insulation in the stud space and R-10 continuous insulation (R-13 / R-7.5 ci in 2012 IBC/IECC ASHRAE 2010).

Stud wall assemblies have much higher requirements (i.e. R-7.07) than masonry mass walls because of the benefits of thermal mass, which are now quantified in the national energy codes. Advantages of thermal mass masonry include:

● reduction of temperature swings;
● moderation of indoor temperature;
● storage of heating/cooling for later release (Figure 6);
● reduction and shift of peak heating and cooling loads to non-peak hours; and
● passive solar design.

(Designers should check National Fire Protection Association [NFPA] 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components, and manufacturer’s requirements when specifying combustible insulation and/or combustible air-moisture-vapor barriers in wall systems—special detailing and letters of engineering equivalency may be required.)

Example 1−masonry cavity wall with 2-in. rigid XPS insulation
A typical 406-mm (16-in.) masonry cavity wall with a 100-mm (4-in.) masonry veneer, 70-mm (2 ¾-in.) air space, 50-mm (2-in.) rigid insulation, an air/moisture/vapor (AMV) barrier, and 200-mm (8-in.) lightweight CMU back-up is shown in Figure 7. Using prescriptive Method B, the ASHRAE table requires an assembly U-factor of U-0.090 or R-11.11 for Zone 5. The resulting R-value of 13.88 exceeds the required minimum of R-11.11 by 25 percent.

If Method A was used, the ASHRAE table requires R-11.4 ci, which, for example, would equal about 64 mm (2 ½ in.) of extruded polystyrene (XPS) insulation or by rounding up to a more common size 76 mm (3 in.). As noted, Method B is not as efficient as Method A. By using only 50-mm (2-in.) XPS (R-10) continuous insulation and the component material R-values, the cumulative assembly (R-13.88) exceeds the required minimum of R-11.11.

Example 2−masonry cavity wall with 3-in. rigid XPS insulation
A typical 406-mm (16-in.) masonry cavity wall with a 100-mm (4-in.) masonry veneer, 45-mm (1 ¾-in.) air space, 76-mm (3-in.) XPS rigid insulation, an air/moisture/vapor (AMV) barrier, and 200-mm (8-in.) lightweight CMU backup is shown in Figure 8. The wall assembly complies with both prescriptive Methods A and B, and exceeds the assembly minimum by 70 percent—this means it is suitable for ‘high-performance’ and LEED projects. The overall wall configuration remains at 406 mm, and the resulting air space is 45 mm.

Example 3−masonry veneer with 6-in. stud backup and 2-in. high-R insulation
Masonry veneer with steel-stud backup is more complex than masonry veneer with CMU backup because of higher minimum R-value requirements due to energy loss through steel studs, cavity width limitations, and dewpoint locations. The maximum cavity (distance from face of steel stud to back of brick) is 114 mm (4 ½ in.) in accordance to MSJC’s Building Code Requirements and Specifications for Masonry Structures, Chapter 12.

This is prescriptive design only and engineering calculations are common for cavities exceeding 114 mm, which require more insulation to meet energy requirements. Also, many manufacturers now make stronger masonry ties, fasteners, and anchors that can easily span wider cavities. The wall configuration in Figure 9 yields a total R-value of 16.04 (U=0.063) which is only three percent over the 2012 IBC/IECC/ASHRAE 2010 requirements, and does not meet 2015 IBC/IECC/ASHRAE 2013 R-value of R-18.18.

It is important to note this wall configuration uses ‘high-R’ (2 1/8-in.) XPS insulation (R-5.6 per inch), which is more expensive than 50-mm (2-in.) XPS (R-5 per inch). This example does not factor in any additional stud backup energy loss, which will vary with stud spacing and wall configurations.

Example 4−masonry veneer with 6-in. stud backup and 3-in. high-R insulation
Figure 10 demonstrates use of 76-mm (3-in.) ‘high-R’ XPS insulation. The cavity has been increased to 127 mm (5 in.), which will require engineered anchors. The resulting 35-mm (1 3/8-in.) air space is well below the 50-mm (2-in.) industry standard, and less than the 38-mm (1 ½-in.) acceptable air space.

One option is to add a 9.5-mm (3/8-in.) continuous drainage mat to assist at preventing mortar bridging, which can lead to efflorescence, water penetration, restricted water drainage and reduced air flow. The net air space of 25 mm (1 in.) would also meet MSJC’s code minimum. Another option would be to simply increase the overall cavity to 140 mm (5 ½ in.), which would result in a 48-mm (1 7/8-in.) air space.

The wall configuration in Figure 10 yields a total R-value of 22.82 (U=0.044), which exceeds the 2012 IBC/IECC/ASHRAE 2010 requirement of R-15.63 by 48 percent, and the 2015 IBC/IECC/ASHRAE 2013 R-value of R-18.18 by 25 percent.

Example 5−masonry veneer with 6-in. stud backup, 2-in. XPS insulation, and R-8 stud space insulation
Another option for insulating steel stud backup walls is to combine rigid cavity insulation with insulation between the studs. In this example, the 114-mm (4 ½-in.) maximum cavity is maintained the air space is an acceptable 48 mm (1 7/8 in.). Caution is advised as a dewpoint analysis is required to reduce the potential for condensation within the stud space. Generally, the maximum stud space insulation should not exceed R-8 in Climate Zone 5 conditions. Most designers avoid additional insulation in the stud space.

The wall configuration in Figure 11 yields a total R-value of 22.04 (U=0.046), which exceeds the 2012 IBC/IECC/ASHRAE 2010 requirement of R-15.63 by 41 percent, and the 2015 IBC/IECC/ASHRAE 2013 R-value of R-18.18 by 21 percent.

The dewpoint theory predicts condensation in a system at any point where the actual and dewpoint temperature lines cross. Figure 12 represents the dewpoint analysis for the ‘Example 5’ stud wall configuration. For this particular assembly, if the rigid insulation was changed to R-10 and the stud space insulation was R-13 as shown for Method A Table 5.5-6 of ASHRAE 90.1 2013, the dewpoint would fall in the stud wall space (Figure 13). This is not recommended.

It is also important to carefully review air/moisture/vapor barrier properties and location within the various wall systems for the building’s climate zone.

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Which bridge to take: Structural or thermal?
Continuous insulation is defined in ANSI/ASHRAE/IES 90.1-2013 (I-P Edition) Section 3.2 (“Insulation”) as:

Insulation that is uncompressed and continuous across all structural members without thermal bridges, other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope. [emphasis added]

Therefore, the code does not require a reduction in R-value calculation for masonry ties, fasteners, or anchors. This is further confirmed in the ASHRAE report, “Thermal Performance of Building Envelope Details for Mid-and High-rise Buildings” (5085243.01 MH 1365-RP July 6, 2011). Brick ties are considered a clear field anomaly, and are not considered practical to take into account on an individual basis for whole building calculation (Figure 14). However, companies now manufacture various masonry ties that provide additional resistance to thermal breaks (Figure 15).

Today, masonry ties must not only effectively hold the veneer in place (especially with wider cavities), but they must also be as energy-efficient as possible while helping to create an airtight seal at the penetration point of the air barrier. New anchors are being developed with ‘thermal breaks’ built into the anchor itself to further reduce any thermal bridges, with 2D and 3D modeling showing that a properly designed thermally broken anchor can improve energy performance of a wall assembly.

‘Gasketed’ veneer anchors are critical to the success of any air barrier system, as those penetrations can not only allow potential moisture infiltration, but also be a thermal weak point that can break the continuity of the building envelope. Obviously, the study of these new anchors primarily is involved with metal stud construction where thermal bridging issues have been most prominent.

Other construction assemblies and connections require closer consideration and evaluation. Examples of these linear anomalies are shelf angles and slab edges. Typical masonry shelf angles can be suspended away from the structure by clip angles or pre-manufactured supports—this allows the rigid insulation to continue behind the shelf angle, reducing thermal loss. Of course, there are still clip angles at periodic spacing (e.g. 1220 mm [48 in.] on center [oc]) as determined by the structural engineer of record that must be considered. These fall into the classification of point anomalies as shown in Figure 16.

It is essential the architect and engineer determine which bridge to take. The structural bridge would favor the shelf angle tight to the structure to reduce the cantilevered loads and save costs. The thermal bridge would use the clip angles to reduce energy costs. How does one decide? Simply add up the costs and compare (Figure 17).

If the added structural cost to add clip angles to the relieving angles for a project is $100,000 and the owner will save $400 month in energy consumption, it will take 20 years to ‘break even.’ While this is just a hypothetical example, it is important to carefully analyze the cost benefits.

It is also important to analyze the entire building envelope, including the percentage of fenestration. If the building has a significant area of glass with R-values of R-3 to R-5, the cost to increase the R-value for a small percentage of the opaque walls at shelf angle may be unwarranted. Once again, evaluations are required.

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Conclusion
There are various masonry wall assemblies to achieve energy-efficient designs that comply with, and exceed, national energy requirements, LEED, and other high-performance standards. It is important to remember that ‘over-insulating’ opaque walls is not always cost-effective. There is a point where thicker insulation with a higher R-value just does not yield a return on investment (ROI). While buildings may consume a great deal of energy, a greater amount is used with electric lights, equipment, HVAC, and plug loads than through the loss of energy with the building envelope.

Traditional masonry walls can be designed using current technology for insulated-ventilated façades that are practical, energy-efficient, and cost-effective. These walls can also be transformed into modern, contemporary buildings.

Notes
1 The term “residential” does not apply to basic single family homes. As its name suggests, ASHRAE 90.1 provides energy standards for buildings “except low-rise residential buildings” based on the following definition: low-rise residential buildings: single family houses, multi-family structures of fewer above grade, manufactured houses (mobile homes), and manufactured houses (modular homes). Energy requirements for these buildings are indicated in the International Residential Code (IRC). (back to top)

Richard Filloramo is area director of market development and technical services for the International Masonry Institute (IMI) New England Region’s Connecticut/Rhode Island Office. He holds a bachelor’s of science in architecture from Ohio State University and an associate’s degree in construction technology from Wentworth Institute of Technology. Filloramo has more than 40 years of experience in the masonry industry, and has been involved with the design, construction, or inspection of more than 5000 projects. He served as the national IMI liaison for building codes and standards and is a member of the Masonry Standards Joint Committee (MSJC)—the code-writing body responsible for the Masonry 530 Code. Filloramo can be reached at rfilloramo@imiweb.org.

Chris Bupp is director of architectural services for Hohmann & Barnard, and has been involved in the construction industry for nearly 30 years with the building envelope as his primary area of expertise. At H&B, he works with architects, structural engineers, and building envelope consultants as an educational resource and as a national speaker and writer on the subject of masonry wall design. Bupp also serves on two committees at the Air Barrier Association of America (ABAA). He can be reached at chrisb@h-b.com.

To Test or Not to Test…? A guide to field quality control

Photo © BigStockPhoto/Vichaya Kiatying-Angsulee

Photo © BigStockPhoto/Vichaya Kiatying-Angsulee

by Sean M. O’Brien, PE, LEED AP, and David Artigas, PE

When properly implemented, field and laboratory testing of buildings and their systems and components can yield a wealth of useful information about construction quality, watertightness, durability, longevity, and other critical performance criteria.

Test results can help designers better evaluate ‘as-built conditions,’ understand any problems with the installation, and develop solutions appropriate to the specific problems that prompted the testing. When improperly implemented, however, testing can yield misleading results, lead designers to incorrect conclusions, and cause unnecessary expenses related to remedial work that may not really be warranted by the in-situ conditions.

In some cases, specifying inappropriate standards or performance criteria can create confusion or incite debate between the design and construction teams, especially in the event of a perceived failure. This article reviews some of the common test methods and procedures used in contemporary construction, with a focus on how the purpose of, and results from, these tests are often misunderstood.

This site-built interior chamber creates differential pressure across a curtain wall system for a test under American Architectural Manufacturers Association (AAMA) 503, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems.

This site-built interior chamber creates differential pressure across a curtain wall system for a test under American Architectural Manufacturers Association (AAMA) 503, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems. Images courtesy Simpson Gumpertz & Heger

The spray rack above has been positioned on the window exterior for AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products.

The spray rack above has been positioned on the window exterior for AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products.

 

 

 

 

 

 

 

 

 

 

 

Most important (but least asked) question
With dozens of industry organizations publishing thousands of test standards for buildings and building systems, there is almost always a quick answer to the questions: “What do I test and how do I test it?” However, the more important question, and one about which designers and contractors are often less sure, is “Why do I test?”

The answer to this question will almost always dictate the best method to use, the timing of the test, the pass/fail criteria, and sometimes whether it should be performed at all. In the case of poorly specified tests, the wrong tests are often performed ‘because it was in the specifications’ or ‘because the contractor owes us testing.’ Especially with fast-track construction projects, debates over testing are often brushed aside in favor of doing whatever the specification demands, regardless of the value of that testing.

In the authors’ experience, requiring designers to explain the reasoning behind their specified test methods or procedures can be an extremely useful exercise, either during the design process or as part of pre-construction activities. In the case of a designer having correctly specified test methods, the discussion can provide valuable information to the rest of the project team, giving everyone involved a better understanding of the reasons behind the testing. For improperly specified tests, the conversation can help avoid unnecessary testing and the resulting time/expense, as well as identify the correct test methods to determine the desired information.

Flood testing of a membrane waterproofing system on a rooftop parking deck occurs the finished paving is installed.

Flood testing of a membrane waterproofing system on a rooftop parking deck occurs the finished paving is installed.

Dye is used to color water during a roof flood test; it can help link interior leaks to specific areas of the roof above.

Dye is used to color water during a roof flood test; it can help link interior leaks to specific areas of the roof above.

Windows, doors, and curtain walls
Some of the most commonly tested building components are fenestration products—windows, doors, and curtain walls. For new construction, testing is most often specified as a quality control measure to ensure the installed system(s) meet the specified performance requirements for air and water penetration resistance.

The most common requirements are for testing in accordance with various American Architectural Manufacturers Association (AAMA) standards, depending on the system being evaluated. This requires the designer or specifier to know what type of system is specified as well as the relevant performance requirements to establish the appropriate test method.

There are different standards for different components, and some contain multiple test methods or options. For example, AAMA 501.1, Standard Test Method for Water Penetration of Windows, Curtain Walls, and Doors Using Dynamic Pressure, includes a method to test curtain fenestration for water penetration under dynamic wind pressure that requires a large fan—essentially, an airplane engine/propeller—and calibrated spray racks. There is also AAMA 501.2, Quality Assurance and Diagnostic Water Leakage Field Check of Installed Storefronts, Curtain Walls, and Sloped Glazing Systems, which is much easier to perform as it uses a simple handheld nozzle to spray along gaskets and joints. In this case, specifying testing per AAMA 501 is insufficient—the specific test method from that standard needs to be called out, as the two options vary greatly in scope and complexity.

In previous versions of the AAMA 501 standard, a third option (501.3) was available to perform water leakage testing under static pressure differential (Figure 1). Despite this test being pulled from the standard and replaced by AAMA 503-02, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems, references to the 501.3 method can still be found in specifications written today. This often results in confusion when the time comes to perform the tests.

AAMA 501.2 is intended as a field check for water leakage—a simple, economical method to verify the general quality of the curtain wall installation. For compliance with a specified level of air- and water-penetration resistance, AAMA 503 must be used. It is important to note 501.2 is solely intended for fixed glazing systems; the high nozzle pressure used would likely cause moderate to severe leakage on operable vents or window products due to the inherent limitations of seals and gaskets used in operable fenestration.

For testing window assemblies (both fixed and operable) for compliance with a specified air- and water-penetration, AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products, is typically specified. This involves building a chamber on the interior of the product to allow for negative interior air pressure and using a spray rack to wet the exterior of the window (Figure 2).

It is important to understand this test method has a specific definition of what constitutes a leak. For example, water on the sill members that does not pass the innermost projection of the window is not considered a leak, since it does not reach a point where it can damage interior finishes. This can come as a surprise to designers witnessing the test and seeing water on the sill, only to find out that by the standard’s strict definition, the window is considered to not have leaked. For this reason, some specifiers add their own language regarding the definition of leakage, but may have difficulty holding a manufacturer to this definition in the event of a dispute.

It is also important for designers to clearly specify the pass/fail criteria for windows. This information can be derived from the performance class (e.g. R, CW, or AW) and grade for the product being tested, but is often misinterpreted, leading to confusion during the test or attempts to hold installers/manufacturers to unrealistic or non-industry-standard performance criteria.

Another caveat of AAMA 502 (since the 2008 revision) as well as AAMA 503 is they only apply to newly installed fenestration products. The standards define ‘new’ as products installed before issuance of the certificate of occupancy for the building or products that have been installed for less than six months.

This recent development is often a source of debate, as this means a window installed for six months and one day, even in an unoccupied/incomplete building, is no longer subject to AAMA 502 and therefore cannot be tested for compliance with the manufacturer’s stated performance criteria. In simpler terms, the manufacturer of the window is only held to its stated performance criteria for six months. For older products, AAMA 511, Voluntary Guideline for Forensic Water Penetration Testing of Fenestration Products, contains diagnostic procedures for identifying known leaks, but is not specifically intended to evaluate in-situ performance of non-leaking windows.

When specifying testing, it is important to make the distinction between test specifications, standard test methods, and testing guides. Each of these types of documents is used for a different, but often similar, purpose. Standard test methods, such as ASTM E1105, Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls, by Uniform or Cyclic Static Air Pressure Difference, contains specific information on how to physically test these various components, what equipment to use, and related information.

Test specifications, such as AAMA 502, provide procedural information on the testing, the relevance/applicability of the testing, and related administrative information, and typically reference standard test methods (e.g. ASTM E1105) for the physical test procedures.

Finally, testing guides, such as ASTM E2128, Standard Guide for Evaluating Water Leakage of Building Walls, are usually more general in nature and cover a wide range of components and procedures rather than focus on one specific area of the building enclosure. Similar to test specifications, these guides include procedural/administrative requirements and reference standard test methods for the actual testing procedures. Due to their non-specific nature, including ‘compliance’ with a testing guide such as ASTM E2128 as a specification requirement is likely to result in confusion, as it can be interpreted in many ways for many different components. A testing specification and pass/fail criteria must be clearly identified in the contract documents.

This depicts laboratory testing of brick masonry for compressive strength.

This depicts laboratory testing of brick masonry for compressive strength.

Water leakage through brick veneer/cavity wall can be seen from the interior through openings in the backup wall. The veneer does not provide actual waterproofing for this assembly due to presence of drainage plane and weather-resistant barriers.

Water leakage through brick veneer/cavity wall can be seen from the interior through openings in the backup wall. The veneer does not provide actual waterproofing for this assembly due to presence of drainage plane and weather-resistant barriers.

Roofing assemblies
Leakage from roofing systems, especially in the case of low-slope assemblies, can result in significant interior damage when left unchecked. There are many different methods for testing roofs, but not all are compatible with all assembly types. Understanding which methods can be used for which systems is key to specifying the appropriate test, whether as part of a specification for quality control in new installations or as part of remedial/troubleshooting efforts.

In this article, the authors focus on large-scale testing of roof areas, as opposed to smaller-scale testing of specific detail conditions (which is most often done using spray racks/nozzles or localized flood testing). As discussed, the roof’s configuration, as well as the specific membrane type, must be considered when specifying a test method.

The most obvious method of testing a roof—flooding it with water—can be effective in some cases, but extremely damaging in others. Flood-testing is best-suited to inverted roof membrane assemblies (IRMAs) where the membrane is installed directly over the structural deck, with insulation and ballast or other overburden above. In those cases, the testing is performed once the membrane and flashings are complete but prior to the installation of any overburden (Figure 3).

For this test, which is standardized in ASTM D5957, Standard Guide for Flood Testing Horizontal Waterproofing Installations, water is ponded over the system for a period of 24 to 72 hours, during which time the interior is reviewed for leaks. The depth of water must be reviewed to ensure the structural capacity of the roof is not exceeded, as every inch of water adds approximately 0.24 kPa (5 psf) of load. This can be challenging on large or complex roofs, where the deck slope may require compartmentalizing the test into smaller areas. Any leaks resulting from this test are likely to produce only localized damage which gets repaired along with the leaking component(s).

This test procedure is not appropriate for traditional ‘membrane-over-insulation’ roof systems, since leakage through the membrane may wet (and necessitate the replacement of) large areas of roof insulation. Especially in the case of a concrete roof deck, leakage through the membrane could go unnoticed or travel far from the original location as the deck retains the water, allowing large areas of insulation to become damaged and making it difficult to determine the leak’s source. These risks can be reduced by flooding only small areas at a time (limiting the amount of water that could enter the roof), in which case the water can be dyed to provide confirmation of leak sources if multiple areas are flooded in sequence (Figure 4).

There are several test methods available for traditional insulated roofing systems that do not carry the same risk of large-scale damage. These methods typically rely on specialized equipment to detect wet insulation below the membrane. Infrared (IR) thermography uses an infrared camera that visualizes temperature differences on surfaces by measuring and processing emitted radiation.

For an insulated roof, wet insulation will tend to retain more heat and cool slower than dry insulation. Since moisture from roof leaks is often trapped in the system for an extended period, scanning of a roof with suspected or known leaks shortly after the sun has set can help identify areas of wet insulation.

The IR camera measures the surface temperature of the membrane, so this method cannot be used on ballasted roofs since the ballast (e.g. gravel) will cool off uniformly and mask any small temperature differences on the membrane below. Similarly, testing on a windy day may yield misleading results as airflow over the membrane surface may even out temperature differences or cause the wet areas to cool off to the same temperature as the surroundings before the scan is made.

IR scanning of a roof is relatively efficient since large roof areas can be surveyed relatively quickly (some companies even offer aerial surveys, which can be economical for very large, open roof areas). A second method, often referred to as electrical capacitance/impedance (EC) testing, uses handheld or rolling (push-cart) equipment that sends electrical pulses into the roof system and measures the insulation’s ability to retain electrical charge. Wet areas will tend to hold a charge for less time than dry, allowing for relative comparison between areas. Similar to infrared, this method requires an exposed roof membrane since the scanner needs to be in close proximity to the insulation to be effective. For this method to be effective, the roof membrane needs to be non-conductive, making it ineffective on most ethylene propylene diene monomer (EPDM) assemblies or on membranes with metallized reflective coatings. For both of these methods, secondary verification (i.e. roof probes) of suspected wet materials should always be specified to confirm the efficacy of the test for the specific application.

A more recently developed test method uses specialized equipment to pinpoint specific defects in the membrane. In this method, a potential difference is created between the wetted roof surface and the grounded roof deck. Any breaches in the membrane create, in effect, a short circuit in the system which can be detected using specialized equipment.

This method can be used on both traditional and IRMA systems, but—similar to EC testing—the roof membrane must be nonconductive for the method to work. For new construction, especially on traditional roof systems, a grounding screen can be added below the membrane or cover board to provide more positive leak detection and become part of a permanently installed leak detection system. This type of system can be especially beneficial for vegetated roofing assemblies where the often significant amount of overburden can make locating leakage sites extremely difficult.

This infrared image shows air leakage around a window perimeter during a whole-building test.

This infrared image shows air leakage around a window perimeter during a whole-building test.

Brick masonry and exterior walls
Brick masonry has been a common building material in the United States since the colonial period, and mass masonry walls continued to be built through the first half of the 20th century. While the basic process of brick manufacturing has not changed much, modern technology allows the creation of brick typically much stronger and has greater uniformity of properties than historic brick. Historic lime mortars typically are softer and more permeable than modern cement mortars, which allows them to absorb greater stress within the wall from expansion and contraction or enables the wall greater capacity to ‘breathe.’

Concerns with historic masonry fall under two, often related, headings: the masonry’s structural capacity and durability. While it certainly is true modern masonry manufactured and constructed to meet modern standards should result in durable construction, it is not always necessary to hold historic masonry to these same modern standards, as the historic materials often have more than the necessary capacity to provide a long service life with good performance. Also, certain properties being lesser than modern standards may prove beneficial to performance.

The International Building Code (IBC) now has requirements for masonry properties such as compressive strength and performance in shear, though that was not always the case. Current codes are written for current construction, and do not always include previsions for how historic construction ‘works’ structurally. The International Existing Building Code (IEBC) includes provisions that allow historic buildings to remain, or repairs to occur, using original or like materials, but the structural engineer and code officials must still evaluate the structure’s capacity to withstand its loads and remain safe.

Structural engineers can use both non-destructive and destructive methods to determine masonry’s strength and ability to withstand stresses (Figure 5). It is important to specify testing appropriate to both the structure being evaluated and the goal of the evaluation. While a historic mass masonry wall may not meet the letter of the current code requirements, it may have capacity that exceeds its in-service loads with an acceptable factor of safety comparable to the code. That said, one concern with mass unreinforced masonry is it typically does not perform well during seismic events. In areas of higher seismic activity, greater care must be exercised in its evaluation.

Current requirements for energy efficiency mandate the building enclosure to have a specified resistance to heat transfer. While mass masonry walls typically have a lower R-value than modern insulated wall assemblies, they have an advantage—their bulk provides thermal mass unmatched by newer assemblies comprising several thinner layers of different materials sandwiched together. This thermal mass allows the wall to absorb and dissipate heat more slowly than modern walls, slowing the interior of the building’s reaction to changes in the exterior temperature and reducing the need for supplemental heating or cooling.

Changes to the thermal properties of a mass masonry wall, such as adding insulation to the interior, or significantly increasing the interior moisture load, may affect brick performance. Uninsulated historic masonry typically allows moisture to move through the wall (i.e. ‘breathe’) while remaining above the dewpoint, since the interior heat warms the wall.

The addition of interior insulation will reduce the wall’s temperature during the colder months. Water absorbed by the brick’s exterior wythe may go through freeze-thaw cycling as a result of the wall now being colder, and interior moisture that migrates through the wall assembly may condense on the inboard side of the masonry wall, because this side of the wall now is on the ‘cold side’ of the insulation.

Historic masonry may have two advantages that will reduce the likelihood of these two events occurring.

1. Historic brick typically is more porous than modern brick. This greater porosity may allow the brick to ‘drain’ rainwater more quickly than modern brick, and the larger pores may allow the absorbed water more room to expand without causing damage.
2. Historic lime mortars are more absorptive and permeable than modern mortars, and these properties may allow the mortar to wick water rather than having it remain on the wall.

However, it must be stressed the reaction of mass masonry to the installation of interior insulation is still a topic of study among engineers and preservationists. Further, there are currently no established guidelines for insulating walls, only various opinions on the matter.

Many designers of renovation projects may equate strength with durability and specify masonry testing with this thought in mind. Great care must be exercised when considering insulating mass masonry walls, and testing of the masonry’s porosity, absorption, permeability, expansion, and relative strength (both of brick and of mortar) should be performed. Additionally, laboratory testing and evaluation to determine the relative durability of the brick, as well as its resistance to freeze-thaw damage, are a crucial part of this kind of study.

It is also critical to evaluate test results in light of numerous factors, such as the type of building/occupancy, building use, and general quality of the surrounding construction. If a sampling of brick test as SW grade (suitable for severe weathering per ASTM C216, Standard Specification for Facing Brick [Solid Masonry Units Made from Clay or Shale]) that does not necessarily mean the wall assembly in question has the level of durability required for the specific application. SW brick on a large, clear wall area will likely provide suitable performance, but the same brick installed in a shaded location (i.e. minimal drying) below a window that experiences leakage (i.e. excessive wetting) may undergo premature degradation regardless of the brick grading.

The most important question to ask when evaluating a historic masonry building is: “How has it performed thus far?” If the building shows no obvious signs of distress after several decades or even centuries of use, its testing and evaluation must begin from a position of “How does it work?” as opposed to one of “Does it meet the code requirements for modern construction?”

This understanding will include site observations and possibly onsite or laboratory testing, and research into historic construction methods and materials. Ultimately, this approach to evaluating historic masonry may lead to a more efficient and lower cost project that also can maintain the building’s character. Regardless of testing, designers who take this approach much understand when the use of the building or other characteristics of the enclosure are changed as part of renovations, the prior performance of the building may not be a suitable predictor of long-term durability.

From a water penetration standpoint, there are many different test methods available for masonry walls, but not all provide useful information. For example, ASTM C1601, Standard Test Method for Field Determination of Water Penetration of Masonry Wall Surfaces, determines water penetration at the surface of a masonry wall, but does not provide any information on how much water actually leaks to the interior (as opposed to water that is absorbed and stored by the masonry). Similarly, RILEM tubes can be used to provide relatively quick evaluations of the water absorption rate of a masonry wall.1

ASTM E514, Standard Test Method for Water Penetration and Leakage Through Masonry, provides for measurement of the actual amount of water penetrating the full thickness of the masonry, but this is a lab test not applicable to field conditions (although it is often specified—incorrectly—by designers evaluating existing masonry buildings). Field surface absorption tests may have limited use in qualitatively evaluating the change in absorption that results from installing a penetrating sealer, but are typically of little to no use in evaluating water leakage.

Neither of these tests will be of practical value for masonry cavity wall construction, where any water penetrating the exterior façade is collected in a drainage cavity and wept out of the system (Figure 6). Water leakage through a masonry cavity wall is more likely the result of a breach in the water-resistive barrier (WRB) behind the masonry, since masonry veneer systems are expected to allow water into the drainage cavity.

The authors have generally found the general guidelines from ASTM E2128, Standard Guide for Evaluating Water Leakage of Building Walls—as opposed to one specific standard test method—are helpful in establishing the right combination of testing and inspection to diagnose water leakage through masonry walls.

Air barrier systems
As far as building testing goes, the testing of air barrier systems is a relatively recent development.2 Just as with window and curtain wall testing, there are multiple test standards and guides for testing air barrier systems in both the lab and the field. One of the first points of confusion is the definition of an air barrier—a system of interconnected components including walls, windows, curtain walls, and roofs that act together to prevent uncontrolled airflow into and out of the building. While air barrier testing is often thought of as testing a wall air barrier membrane (one component of the system), it can encompass everything from single materials to the entire building enclosure.

Some of the most commonly tested building components are fenestration products like windows and curtain walls. For new construction, testing is most often specifi ed as a quality control measure to ensure the installed systems meet the specifi ed requirements for air and water penetration resistance. Photo © BigStockPhoto/Graça Victoria

Some of the most commonly tested building components are fenestration products like windows and curtain walls. For new construction, testing is most often specified as a quality control measure to ensure the installed systems meet the specified requirements for air and water penetration resistance. Photo © BigStockPhoto/Graça Victoria

Testing of actual materials, such as sheet- and fluid-applied membranes, is performed in the laboratory due to the very small quantity of air leakage being measured and the high degree of accuracy required in the measurement. Air barrier products are required by most codes to allow no more than 0.02 L/s.m2 @ 75 Pa (0.004 cfm/sf at a pressure differential of 0.3 in. of water). In reality, most sheet membranes (such as self-adhered rubberized asphalt products) exceed this criteria by an order of magnitude or greater—much too low to be reliably measured in the field.

Air barrier assemblies—essentially, air barrier materials in an as-built condition that includes laps, seams, and penetrations—can be tested in either the lab or the field. Laboratory testing per ASTM E2357, Standard Test Method for Determining Air Leakage of Air Barrier Assemblies, provides an air leakage rate for a pre-defined arrangement of air barrier products, penetrations, and a window opening (but not the window itself—an oft-overlooked element of the air barrier system).

While primarily a laboratory test used by air barrier manufacturers to demonstrate their products’ performance and code compliance, the method can also be applied to field-installed mockups. However, applying this test in the field is not as simple as installing a chamber on the interior and testing the exterior. Air leakage through the perimeter of a sample area (e.g. through a concrete block or stud wall perpendicular to the interior-exterior direction) is often impossible to isolate, and due to the relatively low leakage rates being measured, even a small amount of extraneous leakage can create a false negative test result. Using this general chamber testing approach on a qualitative basis is simpler and often more effective, since telling a contractor that the test result was 0.25 L/s.m2 (0.05 cfm/sf)—in other words, a failure—does not provide the same level of usefulness as telling them there were leaks at one membrane seam and two brick ties that need to be repaired.

Specifications for field-installed air barrier assemblies often include testing of the window as part of the assembly. While this makes sense from a practical standpoint (i.e. the connection to the actual window system is a critical transition in the air barrier), there are limitations to this test. From a practical standpoint, mockup testing of air barrier assemblies typically happens at the beginning of a project, often long before the windows are delivered to the site (or in some cases, before specific window products are even selected). Testing of the assembly with a ‘dummy window’ in place is possible, but results can be misleading since the actual connection is unlikely to be the same as what is intended for the project windows.

In cases where the dummy window is put in temporarily with sealants and sprayed-applied foam insulation, the actual leakage rate may be much lower than what will occur when the project windows are installed, giving a false positive result for the test. In the case of the project windows being available at the time of testing, the specification of pass/fail criteria for the air barrier assembly test becomes more important. The performance criteria for air barrier assemblies are based on a window perimeter being included, but not the window itself. Since most windows will experience significantly higher leakage (on an area basis) than air barrier materials and assemblies, leakage through the window may far exceed the air barrier assembly leakage criteria, even if the assembly itself, minus the window, would pass on its own. For this reason, it is important to clearly specify how and if the window is to be included in the test, and, if so, some increase in allowable air leakage needs to be included to avoid requiring a result which is not attainable in the field.

The third type of air barrier testing is whole-building testing, using blower door or similar equipment and ASTM E779, Standard Test Method for Determining Air Leakage Rate by Fan Pressurization, procedures to measure overall air leakage through the entire building—including all walls, roofs, and windows. Different codes and standards require different overall leakage rates, but 0.02 L/s.m2 @ 75 Pa (0.4 cfm/sf at 0.3 in. of water) is typical for most building and energy codes.

While this test provides a single number to describe air leakage that can be easily compared to other buildings, it has many limitations that must be considered before requiring a certain level of whole-building performance. The first major issue is at the time when the air barrier is substantially complete to the point where testing can be performed, it is also likely to be concealed by cladding and other materials that can make the detection (using IR thermography or tracer smoke) and repair difficult or impossible.

Second, the testing itself can be difficult to perform, especially on large/more complex buildings, due to the need for multiple fan systems that must all be linked together for measurement or adjustment. In tall buildings, internal fans may be needed to equalize pressure differentials over the height of the building. While most testing firms can easily come to a site and perform standard window or curtain wall tests, large-scale testing of whole buildings requires specialized equipment and a fair degree of experience and expertise to successfully execute.

Lastly, there is some debate over what is achievable in terms of air leakage through whole buildings. A designer can certainly specify the overall leakage rate needs to be 0.5 L/s.m2 (0.1 cfm/sf), but achieving that level of airtightness requires an exceptionally well-designed air barrier, as well as carefully planned execution of the construction.

This is a common mistake with all types of air barrier testing—specifying a high level of airtightness without providing the corresponding design detailing is a futile effort. As mentioned, once the building is physically ready to be tested, it is often far too late to practically implement repairs, which brings up the difficult question of “What do we do now that we failed the test?” While the industry is still working on answering that question, specifiers can help avoid problems by specifying reasonable levels of airtightness appropriate for the building design.

As with the other previously described tests, visualization techniques such as infrared thermography and tracer smoke can be used to take advantage of the pressure differential created during a whole building test and qualitatively identify air leakage sites (Figure 7).

Conclusion
While the wide variety of available testing standards means there is almost always a standard for the designer’s specific need, finding the right standard can be difficult when one does not have a firm understanding of the actual goals. Designers and specifiers should first evaluate the question of ‘why’ when it comes to testing, as the answer will typically guide them to the correct test method to follow.

Specifying both the appropriate testing method and the appropriate pass/fail criteria are necessary to provide meaningful test results and avoid the time and expense of unnecessary testing or inappropriate testing which leads to ambiguous results. A little more time spent researching test methods during the design phase and specifying appropriate methods and performance criteria can go a long way toward reducing confusion and disputes during the construction process in the field.

Notes
1 For more on RILEM tubes, see The Construction Specifier articles, “Testing the Test: Water Absorption with RILEM Tubes,” by Adrian Gerard Saldanha and Doris E. Eichburg, and “Durable Waterproofing for Concrete Masonry Walls: Redundancy Required,” by Robert M. Chamra and Beth Anne Feero in the August 2013 and July 2014 issues. (back to top)
2 For more on air barriers, see the article “Wind Load and Air Barrier Performance Levels,” by Maria Spinu, Ben Meyer, and Andrew Miles, in the July 2014 issue. (back to top)

Sean M. O’Brien, PE, LEED AP, is an associate principal at the national engineering firm Simpson Gumpertz & Heger (SGH), specializing in building science and building enclosure design and analysis. He is involved in both investigation/forensic and new design projects. O’Brien is a member of the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE), co-chair of the New York City Building Enclosure Council (BEC-NY), and a frequent speaker and author on topics ranging from building enclosure design to energy efficiency. He can be reached at smobrien@sgh.com.

David Artigas, PE, is senior staff I–building technology at SGH, specializing in building enclosure design and investigation, building science, and historic preservation. He can be reached at djartigas@sgh.com.

Durable Waterproofing for Concrete Masonry Walls: Field Testing Methods of Water Repellency

by Robert M. Chamra, EIT and Beth Anne Feero, EIT

There are two main field testing methods used for water repellency of concrete masonry units (CMUs), for quality assurance before being placed in a wall: droplet and RILEM tube testing. Completed assemblies can also be tested with RILEM tubes or other standard water spray tests such as ASTM E514, Standard Test Method for Water Penetration and Leakage Through Masonry.

Droplet testing
The droplet test is a quick and simple test to observe the water mitigation capabilities of a CMU. This test requires the unit to be placed horizontally on a level surface with the face shell oriented upward. Droplets are placed at different locations around the unit from a height of 50 mm (2 in.) or less.

The specimens are to be placed in ambient temperature (22.9 ± 5.6 C [75 ± 10

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F]) and moderate relative humidity (50 ± 15 percent) and are monitored for evaporation facilitated by sunlight or wind; they are recorded at one-, five-, and 10-minute intervals. At the conclusion of the test, the droplets are classified as standing, partially absorbed, totally absorbed, or dry. Additional testing methods should be implemented to further evaluate failed droplet tests.*

Commencement of a droplet test on a concrete masonry unit (CMU) containing integral water repellent.

Commencement of a droplet test on a concrete masonry unit (CMU) containing integral water repellent.

After fi ve minutes, the originally beaded droplet has been partially absorbed into the CMU containing integral water repellent.

After five minutes, the originally beaded droplet has been partially absorbed into the CMU containing integral water repellent.

RILEM tube testing
The standard RILEM tube can hold 5 ml (0.17 oz.) of water, which correlates with the static pressure of a 158-kph (98-mph) wind-driven rain. The short RILEM tube was developed for porous materials that are unable to pass a standard RILEM test. A short RILEM tube (approximately 2 ml [0.06 oz.] of water) correlates with a 97-kph (60-mph) wind-driven rain.

Both RILEM tubes are plastic cylinders that are securely placed against the unit for testing using an impermeable putty. Once the RILEM tube is attached to the CMU, water is placed into the tube up to the 0 ml (0 oz) mark (top of tube). The RILEM tube is monitored at five-, 10-, 20-, 30-, and 60-minute intervals for any noticeable changes in the water column. Previous testing has shown specimens that hold water for 20 minutes will also typically hold for 60; this allows for shorter experiments. If 20 percent of the water is lost within a 20-minute interval, the CMU is considered to have failed the test—if such losses are not observed, then the CMU has passed.**

A standard RILEM tube is shown at the left CMU cell, while a short RILEM tube is shown at the right CMU cell.

A standard RILEM tube is shown at the left CMU cell, while a short RILEM tube is shown at the right CMU cell.

A standard RILEM tube test has failed on this CMU with integral water repellent.

A standard RILEM tube test has failed on this CMU with integral water repellent.

 

 

* See NCMA’s, Standard Test Methods for Water Stream and Water Droplet Tests of Concrete Masonry Units from 2009.
** See the article, “Testing the Test: Water Absorption with RILEM Tubes,” by Adrian Gerard Saldanha and Doris E. Eichburg in the August 2013 issue of The Construction Specifier. Visit www.constructionspecifier.com and select “Archives.”

To read the full article, click here.

Durable Waterproofing for Concrete Masonry Walls: Redundancy Required

All images courtesy Building Diagnostics Inc.

All images courtesy Building Diagnostics Inc.

by Robert M. Chamra, EIT and Beth Anne Feero, EIT

Single-wythe concrete masonry walls are popular because they are inexpensive to construct, and combine structural support and cladding in one system. However, they can be associated with leakage when the waterproofing design is simplistic. A single-wythe wall can, and should, have multiple waterproofing components.1

Concrete masonry units (CMUs) are characteristically porous building materials. When manufactured in accordance with the industry standard, ASTM C90, Standard Specification for Load-bearing Concrete Masonry Units, commonly used lightweight CMUs absorb up to 17 percent of their weight in water.

CS_July_2014.inddThis porosity is due in part to their composition. The mix for the units contains the usual concrete components of water, cement, and aggregates, but that third component will be a smaller coarse aggregate (i.e. gravel) than cast-in-place concrete. The smaller aggregate decreases the workability of the mix if all other variables are held constant. In some cases, this decrease in workability is compensated by the addition of water to the mix. Similar to cast-in-place concrete, the higher the water-to-cement (w/c) ratio in the CMU mix, the higher the permeability of the units. However, even a good-quality mix will remain permeable (Figure 1).

Furthermore, the geographical location where the CMUs are manufactured affects permeability. The types of aggregate available in different regions varies, which results in mixes with identical proportions of components, but with much different absorption. For this reason, a prescriptive approach for waterproofing CMUs cannot be applied globally. The guidelines for methods of waterproofing remain the same, but the proportions of water repellents must be tailored for the available materials.

An additional factor affecting the porosity of CMUs is the unit-forming process. After the components have been combined, the mix is compacted and vibrated in molds. If properly compacted, a large volume of the interconnected pores within the unit is eliminated. If poorly compacted, the resulting interconnected pores can provide a path for water to migrate through the unit. Even if the overall unit is compacted, extremely porous localized pockets can remain, as demonstrated in the testing described in this article.

Similarly, a CMU containing cracks will be prone to moisture migration. The curing process CMUs undergo after forming will limit shrinkage cracking within the units, but it does not prevent all subsequent shrinkage—especially when CMUs are installed immediately after manufacturing (21 days of curing is recommended). In addition to drying shrinkage, creep (i.e. time-dependent deformation) can occur in concrete masonry walls after sustained loading.2 The resulting hairline cracks from these phenomena will provide routes for water through the unit.

CS_July_2014.inddIn addition to the units themselves, the mortar joints can provide water sources into a concrete masonry wall assembly. If the mortar loses the water it needs to complete curing—due to wind, sun, or suction from the CMUs—shrinkage cracks and separations between units and mortar will develop. Similar to the CMUs, the mortar will also undergo creep after sustained loading—up to five times as much as the CMUs—since the mortar is less stiff than the concrete.3

For waterproofing, cracks within the mortar are worse than cracks within the units, since it is common to have mortar only at the inside and outside faces of the masonry (i.e. face shell bedding). Then, water only has to travel the thickness of the unit wall, approximately 32 mm (1 1/4 in.) to penetrate the assembly (Figure 2).

Recommendations
National Concrete Masonry Association (NCMA) publishes technical articles to provide recommendations for the design and construction of concrete masonry. TEK 19-2B, Design for Dry Single-wythe Concrete Masonry Walls, outlines waterproofing strategies for single-wythe concrete masonry walls at the surface, within the CMU, and at the drainage path. NCMA recommends redundancy to protect concrete masonry from water penetration, including surface repellents or coatings, integral repellents (admixtures), and adequate drainage systems.4

Surface repellents for concrete masonry—typically silicones, silanes, and siloxanes—provide waterproofing at the exterior of the wall assembly. They are applied by a roller or spray equipment after the mortar has had an opportunity to cure. The product is absorbed into the units and mortar and coats the pores. While some products can penetrate deeper, most surface repellents remain within 12.7 mm (1/2 in.) of the CMU surface. In addition to their ability to repel water, surface repellents provide other benefits, such as reducing dirt and staining on the wall’s surface.

Split-face units, shown here being tested with a RILEM tube, are even more challenging to waterproof than smooth CMUs because of the fractured surface.

Split-face units, shown here being tested with a RILEM tube, are even more challenging to waterproof than smooth CMUs because of the fractured surface.

Surface repellents typically allow water vapor to be transferred in and out of the wall, and drying when water does penetrate the assembly through cracks or other penetrations.5 These products have varying ultraviolet (UV) resistance, but most need to be reapplied at intervals recommended by their manufacturers.6

Integral water repellents are available to be incorporated into CMUs as admixtures during manufacturing and into mortar during site mixing to limit water migration through the wall assembly. Since the mortar is mixed onsite and not in the unit plant, it is crucial masons also provide proper admixture quantity and mixing practices for the mortar to avoid a waterproofing weakness within the wall assembly. Integral water repellents also improve efflorescence control. Despite concerns with changes to the concrete’s properties, research has shown integral water repellents do not interfere with the assembly’s bond strength.7

Although it may seem counterintuitive, it is better to use mortar of lower strength to limit cracking.8 High-strength mortars are stiffer; they crack at a lower strain compared to low-strength mortars. Movement related to thermal and moisture changes, as well as foundation shifting, can cause cracking in strong and stiff wall assemblies. These cracks may not impair the wall’s structural performance, but all cracks add opportunities for water’s entry into the assembly.

The mortar’s installation can be as important to the mortar joints’ performance as the materials used. Proper tooling practices help protect concrete masonry walls from unwanted moisture penetration. Choosing a concave or V-joint mortar joint profile will push the mortar against the CMUs to improve bond and provide drainage when the assembly is wet. Raked joints decrease the bond between the CMU and mortar, and provide an area to trap water.9

CS_July_2014.inddIn addition to surface repellents or coatings and integral repellents, NCMA’s other primary recommendation is to provide adequate drainage systems for moisture penetrating the wall assembly. For ungrouted assemblies, through-wall flashing can be installed at bond-beams and floor slabs. Flashing is often eliminated in fully grouted walls to avoid severing the grout which makes it important to consider supplemental waterproofing measures.

These suggestions, along with other considerations found in TEK 19-2B, are given to help ensure moisture will not penetrate the masonry. Although CMUs are characteristically permeable, they can be used successfully in single-wythe walls by following NCMA’s recommendations. Since water penetration can come from various sources, the need for a careful and comprehensive waterproofing approach is essential to providing dry and durable concrete masonry construction.

Laboratory testing
Absorption testing of 24 lightweight CMUs was performed by the authors. Half the units contained an integral water repellent. An informal droplet test was performed initially on selected CMUs from each group; then, all the CMUs underwent a RILEM tube test.10 For additional information about these test methods, see “Field Testing Methods of Water Repellency.”

CS_July_2014.inddThe units tested were smooth-faced CMUs. Split-face blocks, with their more aesthetically appealing surfaces, would likely be even more porous because of the fracturing that creates the appearance (Figure 3).

Absorption testing
To comply with ASTM C90, CMUs must meet maximum absorption requirements dependent on the units—the denser the unit, the less absorption the standard allows. ASTM C140, Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units, outlines the absorption testing procedures to comply with ASTM C90. Each CMU in this study underwent ASTM C140 absorption testing (Figure 4).

The addition of integral water repellent to the CMUs resulted in a 34 percent reduction in absorption (and nearly 50 percent less than allowed by ASTM C90). However, these low absorption values do not correlate with water penetration through the units; the low-absorption CMUs still allowed water to penetrate during water-spray testing. The authors believe this disconnect is a leading reason for leakage in single-wythe concrete masonry walls—the industry standards for the components address absorption, rather than water penetration.

Droplet testing
The CMUs without integral water repellent had droplet test results classified as ‘totally absorbed’—immediately after placing the droplet on the unit, the water was absorbed, but the surface remained slightly damp. For the units with the integral water repellent, the classification was ‘partially absorbed.’ Once the water was placed on the unit, some of the water was absorbed, but there was still partial beading and standing water remaining on the unit. After a five-minute period, most of the beaded water had absorbed into the units with integral water repellent and appeared the same as units without integral water repellent.

CS_July_2014.inddThese observations show an integral water repellent can aid in preventing water from penetrating into the unit. However, the integral water repellent was not impenetrable—some water made its way into the units during the droplet tests. More importantly, there was an extreme range of absorptions on the surface of individual CMUs, which indicates porous pockets of less consolidated concrete were present as described earlier (Figure 5).

RILEM tube testing
The second procedure conducted on the concrete masonry units was RILEM tube testing. When tested using a standard 5-ml (0.16-oz) tube, all 24 specimens failed. However, units containing an integral water repellent were able to hold the water column of a short RILEM tube test for more than 20 minutes with little to no reduction in the water level, thus passing the less-severe testing method.

The units without integral water repellent quickly failed even when tested with a short RILEM tube. In a matter of one to two seconds, the entire water column had been depleted, and significant water penetration could be seen in the unit surrounding the RILEM tube and putty. These results clearly indicate the necessity for CMUs to have deliberate waterproofing components to avoid catastrophic leakage.

Medium- or normal-weight CMUs would be expected to perform better than their lightweight counterparts because research indicates water repellents’ effectiveness correlates with concrete density. This is another reason for water ingress in single-wythe concrete masonry walls—the repellents most commonly employed are least effective on lightweight CMUs. In some regions, lightweight units dominate the market despite their poor water penetration performance. This point alone indicates the benefit of using redundant waterproofing components.

CS_July_2014.inddConclusion
Concrete masonry units are porous structural elements that need to be properly installed with appropriate components to prevent water infiltration in single-wythe exterior walls. High-quality CMUs and mortar (complying with ASTM standards), integral water repellents, and good design and construction practices (following NCMA recommendations) are important steps. However, these measures may not suffice.

Redundant waterproofing components are required because of the likelihood of cracks, mortar joint separations, and variable absorption characteristics in a single-wythe concrete masonry wall (Figure 6). The variability of available materials in a given region supports the need for tailoring the design to achieve the desired performance. Field testing during the construction phase is recommended to confirm performance. Even adding a surface-applied repellent will not stop water from migrating through cracks. An elastomeric wall coating should be considered for crack-bridging ability.11

Notes
1 The authors gratefully acknowledge the continuing support and leadership of David W. Fowler, PhD, PE—the faculty advisor for the research being performed at The Durability Lab, a testing center at The University of Texas at Austin. Also, the authors thank Featherlite Building Products for donating concrete masonry units for lab testing. (back to top)
2 For more, see Failure Mechanisms in Building Construction, edited by David H. Nicastro, PE (ASCE Press, 1994). (back to top)
3 See Note 2. (back to top)
4 See NCMA’s TEK 19-2B, Design for Dry Single-wythe Concrete Masonry Walls. (back to top)
5 See NCMA’s TEK 19-1, Water Repellents for Concrete Masonry Walls. (back to top)
6 See the article, “Testing the Test: Water Absorption with RILEM Tubes,” by Adrian Gerard Saldanha and Doris E. Eichburg in the August 2013 issue of The Construction Specifier. (back to top)
7 See NCMA TEK 19-7, Characteristics of Concrete Masonry Units with Integral Water Repellent. (back to top)
8 See Note 4. (back to top)
9 See Note 4. (back to top)

Robert M. Chamra, EIT, is a project engineer with Building Diagnostics Inc., specializing in the investigation of problems with existing buildings, designing remedies for those problems, and monitoring the construction of the remedies. He participates in the research being performed at The Durability Lab—a testing center established by Building Diagnostics at The University of Texas at Austin (UT). He can be reached by e-mail at rchamra@buildingdx.com.

Beth Anne Feero, EIT, is completing her master’s degree in architectural engineering at UT. She serves as the graduate research assistant for The Durability Lab, which researches and tests the durability of building components, identifying factors causing premature failure. She can be reached via e-mail at bfeero@buildingdx.com.