Tag Archives: Waterproofing

Durability of Water-resistive Barriers

wrb_file opener

Images courtesy Building Diagnostics

by Beth Anne Feero, EIT and David H. Nicastro, PE
Many new water-resistive barrier (WRB) products are being introduced, including liquid-applied membranes. These new products join traditional wraps, self-adhered membranes, felts, and building paper, making for a crowded marketplace. A WRB will be concealed behind cladding, where it cannot be inspected, maintained, or replaced, so it must last for the design life of the building. However, will the new products be durable?

WRBs are required by building codes, and are installed on nearly every building, so it is surprising the industry lacks standardized tests for many fundamental properties of WRB products. To evaluate their performance, 17 WRB products (new and old) were tested in various common construction details, along with accessory products (flashings, tapes, and sealants). This long-term study is ongoing, but has already yielded important observations.

Product selection
As its name implies, the purpose of a WRB is to stop liquid water from penetrating through a wall section. However, more products are sold as air barriers, with a corollary benefit of serving as a WRB—and, in some cases, as a vapor barrier. The products included in this study were confirmed with the manufacturers to function as WRBs, but their marketing literature does not always make that clear. As this industry is rapidly evolving, there is some confusion as to the terminology and functions of these products (Figure 1).

wrb_Fig 1 - rolling

Figure 1: This photo shows a water-resistive barrier (WRB) being applied—
or is it an air barrier? Or vapor barrier? Or weather-resistive barrier? Similar products are marketed differently and can have different capabilities, so the functions must be verified with the manufacturer. Images courtesy Building Diagnostics                                                                        

The 2012 International Building Code (IBC) states that in typical sheathing applications, “a minimum of one layer of No. 15 asphalt felt, complying with ASTM D226, Standard Specification for Asphalt-saturated Organic Felt Used in Roofing and Waterproofing, for Type 1 felt or other approved materials, shall be attached to the studs or sheathing.” A similar statement is found in the International Residential Code (IRC). For stucco and masonry veneer applications, both codes require wood-based sheathing “include a water-resistive vapor-permeable barrier with a performance at least equivalent to two layers of Grade D paper.”

Many buildings are still being constructed with felt or building paper serving as the WRB. However, the industry is shifting toward products that can also serve as an air barrier—sometimes called ‘weather-resistive barriers.’ For their WRB function, these products have to be approved by building officials based on test reports demonstrating they perform as well as paper or felt. This does not seem like a very high bar, but it could be if durability were considered instead of just initial test results (Figure 2).

wrb_Fig 2 - WRB behind masonry

Figure 2: Once the masonry installation is complete, this WRB will be hidden, so it will need to last for the life of the building. The product was just introduced, but only long-term testing can verify design life.

Even if they provide only marginal waterproofing, paper and felt have been in service for decades, so their long-term behavior is well-established. By comparison, a few of the new WRBs have suffered various forms of product failure soon after application, resulting in manufacturers revising the formulations or application instructions (Figure 3).

wrb_Fig 3 - split joint

Figure 3: A WRB split at the sheathing joints before cladding was installed, which points to a concern about the robustness of thin barrier products. The manufacturer of this then-new product helped resolve the problem, and updated its recommendations for how to treat sheathing joints.

For this study, products were selected based on criteria that would be considered by designers and contractors for a multi-family building—one of the largest segments of the construction industry. (Most of these products would also be appropriate for large commercial projects, as well.) Research narrowed the products to those believed likely to continue to be sold in their present formulation—since some test results will not be attainable for several years, it would be pointless to invest in long-term testing of products that seemed questionable during the research phase. Additionally, products with a short allowable exposure time before cladding were eliminated because newer materials are being introduced with longer exposure time. As research indicates other viable products, they will be tested in the future.

Interpreting manufacturer’s instructions
Field investigations suggest most failures are caused by ‘what is on the outside of the can’—in other words, even the best products fail prematurely when the installation instructions are not clear (or followed). Sufficient information from the manufacturer is needed for correct use, including which accessory products are required and appropriate design details for typical penetrations, edges, and openings. Providing explicit, concise, and comprehensive instructions for the designer and installer is essential, but rare.

Before the test specimens were constructed, extensive time was spent researching the manufacturers’ publications. Some of the conditions being tested were not found in the instructions and details. For other products, there were multiple accessory choices that were not clearly defined, leading to possible wrong selections. For most of the products studied, it was necessary to contact the manufacturer to confirm the selections; in some cases, the technical support representatives contradicted the published information (and each other when both local and home-office personnel were contacted). While it is always a good design practice to involve the manufacturer, it would be better for the industry if these common details were clearly conveyed.

Another problem is some of the instructions provided are unrealistic. For example, several of the selected products require special detailing around brick ties, which is not economically viable (Figure 4). Voiding a manufacturer’s warranty is less of a concern than the potential for failures in systems that cannot self-seal such fastener penetrations.

wrb_Fig 4 - tie

Figure 4: This type of fussy detailing around brick ties is required by several WRB manufacturers, but it is not realistic. The cost, sequence of construction, and scheduling burdens would cause contractors to choose another product—or worse, not waterproof these frequent penetrations through the WRB as specified.

Ease of installation
Installers want WRB products that are easy and fast to install—to be economical, they want to avoid mixing multiple components, long drying times, multiple accessories, or fussy sequencing requirements. Keeping systems to the fewest products (such as a primary membrane for the field of the wall and a single accessory for detailing) reduces installation time and the possibility of errors.

The test products were installed by a specialty contractor, whose observations and comments indicated there was a wide range of difficulty in applying the products.

UV exposure rating
There are several new WRB products that are not sensitive to ultraviolet (UV) light, which would therefore make them good candidates to be used behind rainscreen cladding. These sophisticated, engineered cladding systems feature pressure-equalized compartments behind a veneer with permanently open joints, so it is important sunlight not damage the membrane through the joints.

For more common cladding systems, it is important to pay attention to the manufacturer’s published maximum exposure time for WRBs before they are covered with cladding. Interestingly, they each publish a single time limit (typically one to 12 months), but obviously the actual exposure during that period would vary depending on the climate and season. Therefore, the risk of prolonged exposure is uncertain.

Overall, the mockup specimens appear to be performing well, but some damage was already observed before reaching the claimed exposure limit. Most of the test specimens were first exposed in the winter; it can be expected the damage due to UV exposure would be worse if the testing started in the summer.

Contractors want longer exposure time, and the newest products being introduced claim to have this capability. This trend may tempt manufacturers into a marketing ‘arms race’ of sorts. During this research, some manufacturers changed their exposure rating without changing the formulation. The testing described below was designed to evaluate both the current exposure ratings and any increased timeframes claimed in the future. Although longer exposure time benefits the contractor, it is not clear benefit accrues to the owner.

Fire resistance
Performing fire testing is beyond the study’s scope, but the manufacturers’ literature typically addresses this requirement. With recent changes in code requirements (and more expected with the next IBC), water-resistive barriers are now being scrutinized for fire resistance in wall assemblies.

WRBs that are combustible and placed on a building over 12.2 m (40 ft) tall having a Type I−IV construction must be tested in an assembly that passes National Fire Protection Agency (NFPA) 285, Standard Method of Test for the Evaluation of Flammability Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components. A recent trend appears to be WRB manufacturers partnering with various other component manufacturers (including insulation, masonry anchors, and cladding) to create complete wall assemblies meeting this requirement.

Mockup test design
In the first phase of this study, WRB products were tested as part of a complete system. The research outlined above guided the design of mockup test specimens that represent most of the difficult details encountered on a typical project. Each specimen consists of a 0.9 x 0.6-m (3 x 2-ft) simulated wood stud wall segment with the WRB placed on plywood sheathing (except one product with an integral sheathing).

Each specimen contained multiple details a WRB system must be able to handle, as shown in Figure 5:

  • 
sheathing joint at the center (3.2-mm [1⁄8-in.] gap);
  • 
outside corner at the bottom and left edge;
  • window jamb flange at the right edge;
  • octagonal electrical junction box penetration;
  • large-diameter penetration (e.g. dryer vent);
  • small-diameter penetration (e.g. plumbing pipe); and
  • masonry veneer anchor (i.e. brick tie).
wrb_Fig 6 - Specimen Accessory Layout

Figure 5: The design of the mockup test specimens included many common details to explore the capability of each WRB system to seal them, as well as the manufacturer’s instructions. Accessory products were applied in strict accordance with the WRB manufacturers’ requirements. Image courtesy Classic Constructors LP

The details were sealed as required by each manufacturer—not based on what is commonly done in the field (Figure 6). While some of those requirements seem burdensome, the initial testing is intended to evaluate the system as recommended by the manufacturer.

The specimens were hung on metal racks facing solar south to be subjected to high solar radiation (in addition to wind and rain). They were placed vertically to simulate typical wall construction. Laying them back at an angle would have increased solar radiation to significantly accelerate the weathering, but it would eliminate another significant factor in performance: gravity. WRB products are often observed in the field to sag after exposure, which tugs on the flashings (Figure 7).

wrb_Fig 7 - detailing

Figure 6: As its name implies, the purpose of a water-resistive barrier is to stop liquid water from penetrating through a wall section. However, more products are sold as air barriers, with a corollary benefit of serving as a WRB. Image courtesy Classic Contractors LP

Once the specimens are exposed for their documented UV exposure rating, they are partially covered with a cement board to represent siding. This cladding is attached with screws, which tests additional fastener penetrations while also allowing the siding to be removed for observations. Only the top half of each specimen is covered; the bottom remains exposed to observe how the products deteriorate after the specified exposure time.

Clear rigid plastic was installed over the back of the specimens to prevent direct water entry, while allowing monitoring of any moisture penetration or damage from the front (product side). A metal coping protects the top of each specimen, but it is not sealed to the cladding—water can enter above the cladding so the WRB will be wetted by rain even after the cladding is applied (the essence of a WRB).

wrb_Fig 8 - sag REPLACEMENT PHOTO

Figure 7: The flashing sagged at the bottom of this wall. Gravity is a factor in WRB system durability, so long-term test specimens at The Durability Lab are therefore vertically oriented. Photo courtesy Buildings Diagnostics

Besides the large mockup specimens, additional small ones are being tested for material properties, including adhesion, that are beyond this article’s scope. Other small specimens are used for the nail sealability testing described below.

Conclusion
Improving durability requires addressing long-term behavior, which is typically related to weathering and chemical formulation. These aspects of a product’s ‘design life’ will be evaluated during the long-term testing described above; a future article will summarize those findings after sufficient exposure. Some premature failure has already been observed, which indicates the need to be vigilant in product selection regarding claimed exposure ratings.

The research and mockup testing also were designed to evaluate a product’s ‘service life,’ which is often governed by the original installation. The results so far indicate the industry needs better information, instructions, and details from manufacturers. To be economical and durable, an ideal WRB system would include only a few required products that are easy to install, cure rapidly, adhere well, seal around fastener holes, and withstand UV exposure for an extended time. None of the products tested so far met all of these criteria.

The industry also needs standard test methods and product specifications that are applicable to WRBs (and air barriers). Some of these are in development by professional societies, but those will take time to develop. Meanwhile, specifiers should be aware the tests cited by manufacturers may not be applicable to the performance criteria needed for a WRB. Most notably, a product’s claimed ability to seal around fasteners should be scrutinized—this study revealed the test methods and published information are generally unreliable regarding this fundamental property of WRBs.

Note: 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.

 Nail Sealability
wrb_Fig 5 - nail test

ASTM nail sealability testing for roofing products is often cited by water-resistant barrier (WRB) manufacturers. This severe test consists of checking for leaks after driving two nails through a waterproofing product applied to plywood, filling a cylinder with 125 mm (5 in.) of water, and chilling the entire specimen for three days. (An environmental chamber at The Durability Lab is visible in the background.) Image courtesy Building Diagnostics

One of the most important—and least understood—durability characteristics of a waterproofing material is its ability to seal around fastener penetrations. Since there is no industry standard for water-resistive barriers (WRBs), this property is commonly measured by ‘borrowing’ a roofing material specification: ASTM D1970, Standard Specification for Self-adhering Polymer Modified Bituminous Sheet Materials Used as Steep Roofing Underlayment for Ice Dam Protection. Many WRB manufacturers publish that their products pass this test; others are silent about nail sealability.

ASTM D1970 was changed in August 2014 to reference a procedure in ASTM D7349, Standard Test Method for Determining the Capability of Roofing and Waterproofing Materials to Seal Around Fasteners. Although better than the previous method, this is still a ‘borrowed’ roofing standard that requires modification for testing WRBs.

The revised test method, which is still severe, requires placing the membrane onto a piece of 12-mm (15⁄32-in.) thick plywood, 300 x 300 mm (12 x 12 in.). Two roofing nails are driven into the center of the board until they are flush with the membrane. Under the old method, the nails would then be tapped back off of the board 6 mm (1⁄4 in.), but now they remain flush.

After cutting its bottom out, a 4-L (1-gal) paint can is placed atop the membrane over the nails and sealed with silicone. The can is filled with water to a height of 125 mm (5 in.). 
An additional can is placed underneath to catch any leaking water, and this entire specimen is put in a temperature controlled chamber at 4 ± 2 C (39.2 F ± 3.6 F) for three days.

After testing, the specimen is removed to observe any water penetration underneath the membrane, on the plywood, on the shanks of the nails, and in the can beneath the plywood. If moisture is documented in any of these locations, then the test is considered a failure.

Fluid-applied membranes cannot explicitly follow this procedure because it requires the membrane to be removed from the plywood substrate for observation. Additionally, the test method assumes an intervening material (typically a shingle for roof product testing) is placed between the nail and the specimen. It is common to modify the test method to suit the product being tested, but it is difficult to find out what modifications manufacturers made.

The new procedure in ASTM D1970 now requires all completed tests to be reported as a ‘pass’ or ‘fail.’ This seemingly straightforward requirement addressed a significant problem: some manufacturers were performing tests until reaching two passing results, and only reporting those two results. Specifiers should confirm with the manufacturers whether products claiming to “pass D1970” included failed tests and what deviations were made from the latest published test method.

The standard does not explicitly define ‘self-sealing,’ so it is useful to compare similar terms. One manufacturer defines self-sealing as “Capable of sealing itself, as or after being pierced.” This is the closest term for the property needed in a WRB—the ability to self-seal around a fastener penetration without an additional application procedure. That same company defines a ‘self-healing’ material as one with “the structural incorporated ability to repair damage caused by mechanical usage over time.” This is not a common feature of WRB products, but the term is often erroneously used as a synonym for self-sealing.

Another manufacturer refers to a similar term, ‘self-gasketing,’ as “the membrane’s ability to be cut by the threads of a self-drilling screw, then seal under compression (i.e. the screw head compresses the membrane as it is seated providing a positive seal).” This term represents an evolving trend in the industry to downplay intrinsic self-sealing capability in favor of extrinsic gasketing provided by another material compressed over the penetration. Some published requirements for products to achieve self-gasketing would not be possible in an actual wall assembly, so specifiers should be aware of the changing terminology and its implications.

Clearly, these definitions express different characteristics of a membrane’s nail sealability either with the nail, without the nail, or based on the compression of the fastener, respectively. Such a distinction implies whether a secondary sealant, protective coating, or intervening material is needed to seal around fasteners.

ASTM D1970, together with its reference to D7349, provides a direct measurement of self-sealing capability. It is a severe test, it was developed for roofing products, and some modifications are needed to test WRBs. These factors may explain why the standard is not cited by all manufacturers; however, self-sealing is crucial, and should be evaluated for any WRB.

ASTM nail sealability testing for roofing products is often cited by water-resistant barrier (WRB) manufacturers. This severe test consists of checking for leaks after driving two nails through a waterproofing product applied to plywood, filling a cylinder with 125 mm (5 in.) of water, and chilling the entire specimen for three days. (An environmental chamber at The Durability Lab is visible in the background.)

Beth Anne Feero, EIT, is a graduate student studying architectural engineering at the University of Texas at Austin. 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.

David H. Nicastro, PE, is the founder of Building Diagnostics Inc., specializing in the investigation of problems with existing buildings, designing remedies for those problems, and resolving disputes which arise from them. He is a licensed professional engineer, and leads 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 dnicastro@buildingdx.com.

An Overview of Waterproofing Solutions

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All photos courtesy Hoffman Architects

by Richard P. Kadlubowski, AIA
Waterproofing failures are more easily overlooked than roofing problems, so design professionals tend to hear less about them. When compared with a reroofing project, however, a below-grade or interior rehabilitation can be far more disruptive and expensive.

Whereas a roof leak can generally be identified with simple test probes, waterproofing breaches can be challenging to diagnose. Even a seemingly superficial leak can be symptomatic of hidden moisture-related deterioration. For basements, vaults, tunnels, and water features, excavation of overburden is often necessary; in commercial kitchens or lobbies, removal and replacement of fixtures and finishes is frequent.

In most commercial and institutional applications, a complete reroofing project can usually be anticipated every 20 years or so. Waterproofing, because it is so difficult to access, should have a design life as long as that of the building—unfortunately, with so many opportunities for damage, incorrect design, or poor execution, it can fail well before its time. When this happens, architectural investigation is needed to determine the location and cause of the leak, the extent of the damage, and the appropriate remedy.

While it can be a major undertaking to properly identify and correct faulty waterproofing, it is far worse to adopt a patch-it-and-hope-for-the-best attitude. All too often, even well-meaning attempts at treating the symptoms of waterproofing failure serve only to trap or redirect moisture, compounding the problem. While prevention is the obvious first choice for waterproofing success, there are many occasions for error: in design, during construction, and throughout operation. Until the waterproofing deficiency is resolved, the problem will only get worse.

Waterproofing basics
Various components contribute to a waterproofing system, such as drainage composites that direct water away from the structure, tie-ins between façade and foundation membranes, and watertight plumbing in food service areas.

Impervious membranes are one critical component of waterproofing, both for below-grade applications (e.g. foundation walls, basements, tunnels, and vaults) and areas subject to high moisture levels (e.g. fountains, lobbies, kitchens, and mechanical rooms). Waterproofing membranes may be applied on the ‘positive’ or ‘negative’ side.

Waterproofing on a building is typically an impervious material that will prevent water entry; building cladding materials may or may not be actual waterproofing. Most building cladding materials (e.g. brick masonry in a cavity wall assembly or rainscreen systems) are not waterproofing—they are only weather barriers. Similarly, although Tyvek-type materials shed water, they are not true waterproofing.

There is a distinction between waterproofing and roofing that has to be understood. Plaza decks over occupied spaces are waterproofed; the deck is technically not a roof. The manufacturers will make this distinction, because also typically waterproofing applications do not come with as complete a warranty coverage as do some roofing systems.

Positive-side waterproofing
By creating a waterproof barrier on the side of applied hydrostatic pressure, positive-side waterproofing prevents water from entering the wall. For a foundation, this would be the outside surface, closest to the soil; for a fountain, it would be the inside (i.e. where the water is).

For below-grade applications, the earth can be banked back such that a positive-side membrane is installed after the foundation is set. In urban areas, this may not be an option. Blind-side waterproofing incorporates the waterproof membrane on the face of the shoring before the foundation is cast. Concrete is then poured, and the waterproofing fuses to the foundation wall as it cures.

Options for positive side systems include:

  • fluid-applied membranes—similar to those used in roofing applications, they roll or brush on as a liquid and cure to form a monolithic, seamless membrane;
  • sheet systems—also similar to those used on roofs, including single-ply thermoplastics and rubberized asphalts;
  • hybrid systems—combining a fluid-applied membrane with embedded fabric reinforcing to create a stronger, more resilient waterproof barrier; and
  • bentonite clay—a natural mineral derived from volcanic ash and applied as a sheet, mat, panel, or spray to swell in the presence of moisture to create
    a solid clay barrier.

Positive-side systems, used both above and below-grade, are generally preferred over negative-side applications for their effectiveness. The structural barrier is completely protected from corrosive chemicals in groundwater, as well as freeze-thaw cycle damage.

The shortcoming to positive-side systems lies in leak detection and remediation. Once backfill is in place, the actual condition of the waterproofing cannot be inspected without excavation. If the system fails, rehabilitation can involve major excavation and reconstruction of paving, landscaping, and wall systems.

Blind-side waterproofing is similar to positive-side methodologies, but once the concrete is poured, the waterproofing is buried and cannot be inspected. Even for membranes installed after concrete is cast, it is too late to correct for sloppy installation once the waterproofing is buried.

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Negative-side waterproofing injection via ports along a foundation wall crack. The gauge monitors the pressure of the injected resin.

Negative-side waterproofing
Negative-side waterproofing protects the surface opposite the side of applied hydrostatic pressure (e.g. the inside of a basement wall), such that water is redirected after it enters the substrate. Negative-side waterproofing materials include:

  • cementitious systems—a combination of chemical waterproofing additives or acrylics with cement and sand to achieve an impervious surface;
  • acrylic, latex, or crystalline additives—products that penetrate into the surface to provide water protection.

Since the negative side is more accessible, it is easier to identify leak locations than with positive-side systems. Negative-side coatings or injections also can be applied as a retrofit measure.

On the downside, with negative-side waterproofing, moisture still enters the wall assembly, which can cause components to degrade over time. The constant presence of moisture can also lead to mold growth, corrosion, concrete deterioration, or damage to interrelated building elements like floors or windows.

Combination systems
For sensitive spaces below-grade, more sophisticated systems have been used. As an example, a rare book vault built below the water table employed a wall-within-a-wall arrangement, with a pump system in the channel between the inner and outer walls to augment the positive side membrane.

Dampproofing vs. waterproofing
Even some seasoned design/construction professionals mistakenly use the terms dampproofing and waterproofing interchangeably, but they are not the same. Dampproofing is a bitumen-based or cementitious treatment applied to the positive side of foundation walls. The quick, inexpensive coating aims to discourage moisture from wicking up into below-grade walls through capillary action. Named for the tiny, thin apertures, or capillaries, in porous materials like masonry and concrete, capillary action moves water from damp to dry areas, sometimes against gravity.

Waterproofing represents a much broader class of moisture protection. Unlike dampproofing, which cannot bridge cracks, a waterproof membrane can stretch to accommodate some degree of differential movement, settlement, and shrinkage. Even when subjected to the hydrostatic pressure of a high concentration of water, waterproofing is designed to be flexible and durable.

Dampproofing is not a substitute for waterproofing. While sometimes used because they are far less expensive than a waterproof membrane, dampproofing products are of a lesser grade and are applied as a sparse coat with little attention to detail. Waterproofing membranes demand precise application and detailing, and they can be reinforced with integral fabrics for increased stability. Dampproof coatings may be cheaper at the outset, but the long-term durability and effectiveness of properly selected and installed waterproofing are well worth the extra up-front cost.

 

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Before: Below-grade windows can present maintenance challenges, as leaves and debris clog drains, encouraging moisture retention.

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After: Adding channel drains and replacing packed earth with drainage media helps direct water away from the building.

 

 

 

 

 

 

 

 

Waterproofing failures
Even seemingly minor evidence of moisture may presage waterproofing distress. Examples include:

  • blisters or peeling paint;
  • mold, mildew, and vegetative growth;
  • dampness or dribbles of water;
  • stains and rust;
  • odors;
  • efflorescence, or white powdery deposits;
  • cracked walls; and
  • wood rot.

Moisture-related deterioration becomes more costly to repair the longer it is allowed to progress. Keeping a record of water infiltration symptoms is important to establishing how, where, and when moisture is penetrating the waterproofing system. An action plan for signs of water entry can involve six steps.

1. Review the leak history.
It is important to note how the building responds to weather events, such as high humidity, rain, or snow. Temperature fluctuations affect building materials, so any correlations with moisture observations should be recorded.

If the leak is worse after it rains, surface runoff is the likely cause. The joints between walls and slabs, as well as conduits, must be checked. However, when the leak is constant (i.e. uncorrelated with rain), it may be caused by a water line—either potable or sanitary sewer. Even an adjacent excavation or infill construction can indirectly lead to leakage by causing differential settlement cracks or changing water flow.

When the leak occurs after using certain equipment in a kitchen or mechanical room, one should perform usage tests to identify the faulty component. If water bubbles up between the foundation wall and the slab-on-grade, rising groundwater levels may be the issue, or a combination of groundwater and surface runoff. Flash storms can overflow combined sanitary and storm sewers, raising the water table. Clogged or inadequate perimeter/footing drains can also contribute to the problem.

2. Identify the water source.
A water test can determine which type of water is leaking. If the water contains chlorine, it is potable (drinking) water, and the source is likely a plumbing leak. If the water has a high coliform count (e.g. e.coli bacteria), a sewage waste line is the problem. If the water tests negative for both of the above, it is most likely groundwater or stormwater.

3. Rule out ambient moisture.

HoffArch08

Excavation exposed deficient waterproofing with this bent water stop in the vault wall.Where there is a significant temperature differential between inside and outside, condensation—not leakage—may be the culprit. To test, a piece of impervious material, such as aluminum or plastic, can be secured to the wall where moisture has been observed.

After a few days, if the sheet is wet on the side facing the wall, water intrusion through the wall surface is most likely the problem. If moisture appears on the side facing the room interior, condensation may be the cause of observed moisture, which can be addressed by adjusting HVAC equipment or improving ventilation.

4. Determine the leak location.
Water is deceptively migratory—the spot where stains or cracks are observed can be quite remote from the site of water entry. Recording when, where, and under what conditions signs of moisture are present can help determine the water access pathway. Original as-built drawings and construction specifications provide clues as to potential weak spots in the waterproofing system.

Non-destructive testing may be useful in identifying leak locations. Flood tests saturate an area, such as the backfill at a foundation wall, to generate conditions conducive to moisture penetration. Waterproofing failures can then be noted and addressed. Additives, such as dyes or scents, incorporated into the flood test water can help identify leaks that are otherwise difficult to detect.

Once the investigation determines a probable location, exploratory openings and test probes can verify the source of the leak.

5. Resolve the leak.
A course of corrective action may include drainage improvements, injections at interior surfaces, and water barriers at penetrations.

Drainage improvements
Stormwater leaks can often be resolved by redirecting water away from the foundation. Repair areas include:

  • improperly connected leaders and gutters;
  • downspout extensions too close to foundation walls;
  • clogged roof drains and gutters;
  • flashing failures in pools or planters;
  • expansion joint failure at plazas and pedestrian tunnels;
  • leaking underground oil storage tanks causing membrane disintegration;
  • backfill settlement directing surface water to footings;
  • improper drainage and seals at stairways, window wells, and openings; and
  • inadequate subsurface drainage.

Injections at interior surfaces
Resolving cracks through injection with epoxy, hydrophobic, or hydrophilic resins can be an economical way to solve minor waterproofing problems without excavation and reconstruction. However, this approach relies on trial-and-error, as it is nearly impossible to know what conditions are on the other side of the wall without seeing firsthand.

In one anecdote from a waterproofing contractor, injections were used to resolve failures in an aquarium tank. The job went over budget as more and more material was required to fill cracks. When the team finally finished and tried to refill the tank, nothing happened. The sealer had penetrated directly into the water system, filling conduits and clogging the pump. Repair costs far exceeded the initial project budget. The lesson—where injected materials have the potential to penetrate subsurface systems, it is probably best to take the known cost of investigation, excavation, and repair over the unknown cost of blind injection.

Water barriers at penetrations
Appropriate moisture protection, including sealants, should be installed at penetrations. However, unless moisture problems are stopped at their source, such barriers may only serve to re-direct water to another weak point. Good sealant integrity is important, but it is really a secondary waterproofing provision. The primary measure is to control moisture levels.

6. Repair the damage

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Liquid waterproofing and application of deck waterproofing with reinforcing fabric.

Once the leak has been resolved and deterioration arrested, water damage to walls, fixtures, and finishes may be required. In concrete structures where water infiltration has led to reinforcement corrosion, steel should be repaired and sealed, followed by application of a compatible concrete patching mortar. Migrating corrosion-inhibitors, either integrated into the patching compound or applied as a surface sealer, can provide additional protection to the structure.

For outdoor areas, including plazas, sidewalks, and landscaping, some rehabilitation may be necessary following waterproofing remediation. If repair work involved excavation, or if leaks have damaged fixtures or dislodged pavers, then outdoor finishes and plantings may need to be reconstructed. Portions of the façade may also require rehabilitation.

Where leaks migrate into occupied space or originate at an indoor area, water-damaged drywall, trim, paint, ceiling tiles, flooring, and fixtures may need to be replaced once the new waterproofing system is installed. Moisture also can lead to mold growth—
a health hazard that may require professional removal and cleaning.

The longer a leak is allowed to progress unchecked, the more extensive the underlying deterioration can become. Stopping a minor leak is far easier than rehabilitating the damage resulting from a major one.

Causes of waterproofing failure
There are a variety of potential causes for the wide array of many possible waterproofing issues.

Design omission
In cases where unusual intersections, multiple penetrations, or differential pressures demand elaborate detailing, designers are sometimes guilty of leaving these vital junctions to the contractor’s discretion. Where a waterproofing construction team has had success with similar configurations in the past, this may not cause a problem. In the more likely event the general contractor is facing an unusual arrangement demanding sophisticated design, relying on standard details is probably insufficient. It is the designer’s responsibility to detail any situations in which waterproofing might be compromised.

Installation error
Even the most rigorous and exacting drawings and specifications are of little use when workers fail to take care with materials and installation. Careless backfilling is a primary source of waterproofing failure, as is damage from heavy equipment. For example, the contractor at a below-grade book vault rushed to pour concrete walls without regard for delicate water stops, crumpling them in the process and rendering them useless. The resultant water infiltration required extensive excavation, concrete repair, and waterproofing rehabilitation to resolve.

Deficient quality assurance
Oversight and review during construction by an owner’s representative is an essential part of the quality control process. Should site conditions differ unexpectedly from design documents, or unforeseen circumstances present themselves, an onsite architect or engineer can respond to last-minute changes without delaying the construction schedule. The design professional can direct the general contractor to protect the work of the waterproofing installer from damage during construction.

HoffArch15

Suspending all kitchen operation for waterproofing rehabilitation is hardly desirable. However, if leaks are ignored, water damage to structural systems and finishes will only make things worse.

Having a site representative present during construction is important to see installation proceeds according to design intent. Eliminating this important part of the design process is often justified by owners with claims of guarantees or, failing that, litigation. Although field reports and photographs can serve as evidence at trial, the real benefit to onsite quality assurance lies in avoiding waterproofing failure in the first place. Submittal review and formalized inspection can make the difference between a successful waterproofing project and catastrophic failure.

Conclusion
For even the best-performing systems, it is prudent to remain vigilant for signs of trouble, so burgeoning problems can be stopped before they get out of hand. In new construction situations, owners can avoid costly waterproofing rehabilitation through appropriate design, correct application, and due diligence during construction. Owners and managers of older buildings have to deal with what they have got—and, often, that means addressing inexpertly designed or incorrectly installed moisture protection systems.

With thoughtful investigative work and creative water management strategies, even the most demanding waterproofing problems can be successfully addressed. The best approach is to waterproof basements, tunnels, mechanical rooms, below-grade levels, kitchens, vaults, water features, and sensitive spaces diligently and correctly from the outset.

 

Glossary of Waterproofing Terms
Blind-side waterproofing: Installation of waterproofing membranes and drainage before the concrete foundation is poured.Capillary action: Movement of liquid in porous materials or thin tubes (capillaries), due to attraction between the molecules of the liquid and those of the solid.

Condensation: The change in phase from a gas to a liquid, as when water vapor cools to liquid water.

Dampproofing: A coating that has been designed to limit soil moisture penetration.

Efflorescence: A white crystalline or powdery crust, made up of dissolved salts deposited by water seepage after evaporation.

Hydrostatic pressure: The force exerted by a fluid, such as water, due to gravity.

Negative-side waterproofing: A barrier opposite the side of applied hydrostatic pressure (e.g. the interior of a foundation wall), whereby water can enter the wall but not pass through it.

Positive-side waterproofing: A barrier on the side of applied hydrostatic pressure (e.g. the exterior of a foundation wall), such that water is blocked from entering the surface.

Waterproofing: A system designed to prevent and manage water infiltration that may include coatings, membranes, drainage media, perimeter drainage, interior channels, sump pumps, or other elements.

 

Richard P. Kadlubowski, AIA, is senior vice president and director of architecture with Hoffmann Architects, an architecture and engineering firm specializing in the rehabilitation of the building envelope. As manager of the Washington, D.C., office, Kadlubowski resolves complex waterproofing situations for existing buildings and new construction, including fountains, kitchens, lobbies, below-grade structures, terraces, and plazas. He may be reached
at r.kadlubowski@hoffarch.com.

 

 

 

 

Protect the Roof

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

One of the most critical (but often neglected) components in ensuring ‘watertightness,’ the roof assembly is typically installed early to protect the unfinished building from water penetration, enabling interior work to advance. However, this early sequencing requires the installed roof to withstand construction traffic and potential abuse for the remainder of construction while vertical wall assemblies, mechanical equipment, and other systems are being completed. Additionally, because roof surfaces provide convenient storage areas for building materials and equipment, and support for suspended scaffold or other means of access, completed roof assemblies can be vulnerable to damage from such construction-related activities.

Although the roof membrane is protected from damage from some material and provided with general pathways for workers, sheet metal panels and other construction-related materials are staged away from the pathways without any protection of the single-ply roof membrane. Photos courtesy Jeffrey N. Sutterlin

Although the roof membrane is protected from damage from some material and provided with general pathways for workers, sheet metal panels and other construction-related materials are staged away from the pathways without any protection of the single-ply roof membrane. Photos courtesy Jeffrey N. Sutterlin

Over the past decades, single-ply membranes have increased in popularity for low-slope applications due to perceived advantages in installation, scheduling, energy efficiency, and pricing. In contrast to multi-layered built-up roofs (BURs), single-ply membranes—typically thermoset or thermoplastic polymer—consist of a relatively thin, single layer of waterproofing protection, resulting in an increased susceptibility to damage during construction. Although many single-ply membranes are reinforced to add strength, puncture resistance, and dimensional stability, when membrane damage does occur, it can result in leakage to the underlying roof assembly and building interior.

While the roofing industry generally acknowledges the importance of properly protecting a completed membrane from construction traffic and unintentional abuse, there are few guidelines regarding temporary protection. Instead, the industry appears to rely on the conventional wisdom of competent field personnel. However, common sense does not always prevail.

A hard-wheeled lift is used to access higher reaches of the roof enclosure without benefit of protection of the membrane. Workers are welding over the unprotected membrane—an activity that resulted in holes in the membrane from weld spatter.

A hard-wheeled lift is used to access higher reaches of the roof enclosure without benefit of protection of the membrane. Workers are welding over the unprotected membrane—an activity that resulted in holes in the membrane from weld spatter.

Recommended practices to protect single-ply roof membranes include:

1. Storage of material and equipment on completed roof membranes should be avoided. Where unavoidable, caution should be taken not to overload the assembly or underlying structural system and to provide proper membrane protection. Structural plywood sheathing over high-density rigid insulation has been found to provide low-cost, but effective, protection.

2. If construction traffic is anticipated in certain roof areas or pathways, a temporary walkway or layered protection should be provided.

3. The completed roof membrane should be constantly monitored and cleaned to prevent accumulation of sharp objects and/or debris that could damage the membrane.

4. Materials that may adversely affect the roof membrane should be identified and their proper use (and required membrane protection) understood and closely monitored.

5. On completion of construction activities, the roof should be thoroughly cleaned and inspected, with any damage repaired. Should membrane damage occur, infrared thermography or low/high-voltage scanning equipment can be useful for identifying moisture within the assembly.

6. Specifications and quality control procedures can be strengthened to ensure proper protection of completed roof assemblies.

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 (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 the Princeton, New Jersey, office of WJE, specializing in investigation and repair of the building envelope. He can be reached at dpatterson@wje.com.

Jeffrey N. Sutterlin is an architectural engineer and senior associate with the Princeton office of WJE, specializing in investigation and repair of the building envelope. He can be reached at jsutterlin@wje.com.

Waterproofing for CMUs: What About Stucco?

In the July 2014 issue of The Construction Specifier, we published the article, “Durable Waterproofing for Concrete Masonry Walls: Redundancy Required,” by Robert M. Chamra, EIT and Beth Anne Feero. A month later, we received the following e-mail from G. Michael Starks, president of the Florida Lath & Plaster Bureau (FLAPB):

I thought this article offers sage advice should your plans call for struck and painted concrete masonry unit (CMU) walls. Unfortunately, the predominance of walls today are not struck and painted, but rather have some other exterior finish applied, such as stucco. In this case, recommending a waterproofing admixture or surface sealer without the caveat that doing so will greatly impair the bond of the stucco to the wall is a bit disingenuous. Applying sealers to the CMU prior to plastering requires further bond augmentation where stucco is specified.

The bond of the stucco to the CMU is achieved by the concrete masonry absorbing the water from the fresh stucco. This absorbed water carries the cement paste into the voids in the CMU (a process commonly known as ‘wetting out’), where it cures and locks the two together. Sealing the CMU before stucco application renders this process null, and results in the future debonding of the stucco from the CMU.

ASTM C926, Standard Specification for Application of Portland Cement-based Plaster, includes a Section 5.2, which discusses remedies when bond cannot be achieved over solid bases. Sealing the CMU voids all but one of the possible augmentation procedures and leaves only the last resort of applying a lath and accessories system to the CMU. As stated in C926:

5.2.3. Where bond cannot be obtained by one or more of the methods in 5.2.2, a furred or self-furring metal plaster base shall be installed in accordance with Specification C1063.

In effect, the other six recommendations required before lathing is approved are disregarded by the recommendations provided in the article. The seven means by which to achieve bond provided in ASTM C926 are listed in decreasing order of effectiveness. As such, there is intent for the application of lath to be last in that order. The addition of lath and accessories creates a huge differential in movement characteristics resulting in much higher cracking potential.

Additionally, the installation of lath over a solid substrate, such as CMU or concrete, introduces another challenge in the anchorage and fastening system required to attach the lath and accessories. Finally, from an economic standpoint, stucco applied over lath systems costs three to four times that of stucco direct-applied to the CMU.

Testing performed by the National Concrete Masonry Association (NCMA) indicates the stucco renders the wall as waterproof as (if not more than) those where admixtures and sealers are applied.

Early in this article, there is a statement about shrinkage cracks that occur in unit masonry. These are a result of the same absorption process discussed earlier though with the mortar and CMU. Many of these can easily be prevented by specifying a leaner mortar, such as Type N. In the circumstance where a cement-rich Type M or Type S mortar is specified, proper masonry workmanship can also mitigate the shrinkage effects, such as requiring the masons to fog their walls after initial set and prior to leaving the site in the afternoon much as the plasterers are required to do (ASTM C926) for the stucco. This process averts rapid water loss (volume) during the hydration process, thus minimizing the propensity for shrinkage crack formation.

In conclusion, if you want to waterproof your CMU and you plan to stucco it—seal the stucco, not the CMU. This at least puts the waterproofing on the positive pressure side of the wall.

One of the article’s co-authors— Mr. Chamra—reached out to Mr. Starks, and allowed us to share his response here.

We appreciate the feedback; we concur with your recommendations with stucco applied over CMU. Our article focused on CMU walls because single-wythe without stucco is used in Texas, and there is a lack of knowledge on how to treat them. There is more knowledge on how to waterproof stucco, but this was outside the scope of this article. We also did not discuss other finishes over CMU for the same reason—that topic could be another article in and of itself. Your letter is a good clarifier if our intention was not clear within the article. Thank you for your time and feedback.

Finish Failure

David Nicastro 2013-02-16 bFAILURES
David H. Nicastro, PE, F.ASTM

 

Elastomeric wall coatings (EWCs) are an important part of new and remedial construction, protecting cladding from water penetration. Assuming they are properly applied, premature failures of EWCs typically involve their manufacturing formulation—degradation due to inadequate ultraviolet (UV) radiation resistance, or cracking due to inadequate low-temperature crack-bridging ability. The photo below shows a problem caused by formulating, but not by the manufacturer.

Failures Column - faded coating DSC06672Like paint, an EWC serves as a finish as well as a protective coating, so durability should be evaluated on aesthetic performance, as well as sealing ability. The photo depicts a portion of a hotel that was coated with an EWC. Although the coating worked as intended to remedy water infiltration, it faded very quickly to the salmon color at the top. The selected color was tan, as shown being re-applied at the bottom. Some colors are inherently more stable than others, but that could not explain this problem—tan is not a challenging color.

In our failure investigation (with the manufacturer’s assistance), we discovered the local coating supplier made two errors. First, it used the wrong tint base. It is common for coatings to be stocked in a white base by local suppliers, who then tint them to match any color by adding pigments. This manufacturer provides the coating in several bases to be compatible with different pigment combinations, but the supplier did not know the difference between them.

Secondly, the supplier used organic pigments subject to fading, rather than the specified inorganic (mineral) pigments. Again, the supplier did not know the difference. Both types of pigments will match the selected color initially, but some organic pigments fade rapidly in sunlight—less than a year in this case.

Since this EWC was a high-quality product, the remedy simply required applying a new topcoat formulated with the correct tint base and pigments. However, a financial remedy was harder to achieve—the scope and liability of local supply shops are not typically addressed by specifications, contract documents, or project insurance coverage.

Specifiers should discuss with the coating manufacturer the UV stability of particular colors, and how to specify the proper tint base and pigments to achieve a durable finish.

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

David H. Nicastro, PE, F.ASTM, started the Failures column for The Construction Specifier in January 1994. He is the founder of Building Diagnostics Inc., specializing in the investigation of problems with existing buildings, designing remedies for those problems, and resolving disputes arising from them. He is a licensed professional engineer, and leads the research being performed at Building Diagnostics’ testing center, The Durability Lab, at The University of Texas at Austin. He can be reached by e-mail at dnicastro@buildingdx.com.