Tag Archives: B2010.10−Exterior Wall Veneer

Weep Now or Weep Later: Moisture management and risk zones for masonry

All images courtesy Masonry Technology Inc.

All images courtesy Masonry Technology Inc.

by John H. Koester

Three decades ago, this author was issued his first patent; it was for a weep system. The main ‘claim’ was the forming of a mortar bed joint’s bottom side to create tunnels or channels into the cores or cavities of masonry walls. In the process of researching information for the patent’s content, something became very apparent—many of the industry-standard accepted practices for weeping had little to no scientific basis.

The spacing of weeps 406, 813, 1219 mm (16, 32, or 48 in.) on center (oc) is one example of a common practice without scientific support given moisture management and modular spacing patterns have little correlation. While there may be rules calling for certain spacing (i.e. 2006 International Building Code [IBC] 2104.1.8−Weep Holes), that does not mean there is supporting research.1 Some things are just done long enough they become standard practice.

With the old weep technology and its spacing, water indeed got out of the cavities and cores of masonry walls. However, it was not necessarily all the water, always through the weeps, or a fast process. Moisture management in masonry walls is about getting the water away from, off of, and out of the construction detail as quickly as possible. The length of time moisture remains is in direct proportion to the amount absorbed into the materials.

What is a weep?
In the first volume of its Masonry Training Series (1996), the Mason Contractors Association of America (MCAA) defined weeps as “openings placed in mortar joints of facing material at the level of flashing, to permit the escape of moisture.” In other words, they allow the exit of any liquid water that drained down to the top surface of a flashing from the masonry wall’s core or cavity.

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The bed joint of mortar needs to be spread (a). Then, a masonry unit is laid (b). Mortar is displaced to allow for wee placement (c), and the air vent material is placed (d). A bed joint of mortar needs to be re-spread in front of the air vent material (e). Finally, a masonry unit is laid to the air vent material and into the bed joint of mortar (f).

The bed joint of mortar needs to be spread (a). Then, a masonry unit is laid (b). Mortar is displaced to allow for wee placement (c), and the air vent material is placed (d). A bed joint of mortar needs to be re-spread in front of the air vent material (e). Finally, a masonry unit is laid to the air vent material and into the bed joint of mortar (f).

Some have incorrectly adopted use of head joint air vent material and devices as weeps. Many of these air vent devices are not the proper dimensions to accommodate potential variations of a first-course bed joint of mortar and masonry unit. The non-voided portion of the bed joint of mortar becomes a dam that causes water to form a reservoir at the bottom of the cavity (Figure 1). Further, installation of this type of material—even when field-fabricated to the right height—is labor-intensive and a cumbersome, multistep process (Figure 2).

The appropriate detail for a masonry air vent and mortar weep.

The appropriate detail for a masonry air vent and mortar weep.

The appropriate detail for a masonry air vent and a masonry weep would look like Figure 3. The weep holes are at the lowest point of the masonry wall (and cavity) and are spaced 267 mm (10.5 in.) apart to improve the mathematical chances one of them will be at the lowest point of the masonry wall (and cavity) where the water is. (The bottom side of the bed joint of mortar is not part of the modular layout of the wall; therefore, the forming of the bottom side of the bed joint of mortar to create a weep system is also separate from any modular considerations.) The masonry wall air vents should be spaced every third brick head joint, one to two courses above the bottom of the cavity, and above the weeps. They should also be a course below the top of the vertical height of the flashing mechanically fastened to the backup wall.

This detail provides excellent weeping capacity and potential air intake to improve airflow in the masonry wall’s cavity. The positive outcomes include improved chances for pressure equalization of the cavity with the pressure on the masonry wall’s exterior surface. This may move moisture-laden air (i.e. water vapor) deeper into the exterior building envelope due to the the scientific principle of high to low pressure equalization. Additionally, providing equal air intakes and air exits at the wall’s top and bottom improves airflow in the core or cavity. This will have some positive impact on the masonry wall’s ability to dry out.2

Commonly used on lintels and shelf angles, open-head joints have the potential to provide both weeping capacity and airflow (Figure 4). They also eliminate problems with the related bed joint of mortar because the first brick course is usually laid dry on the flashing material covering the lintel or shelf angle that waterproofs the bottom of the cavity.

Open-head joints are weep details commonly used on lintels and shelf angles.

Open-head joints are weep details commonly used on lintels and shelf angles.

Sometimes, the bed joint of mortar is left in place because raking it out is not architecturally appealing (it breaks the coursing lines of the bed joint).

Sometimes, the bed joint of mortar is left in place because raking it out is not architecturally appealing (it breaks the coursing lines of the bed joint).

When employed with a bed joint of mortar, there is a chance the bed joint directly below the open head joint will not be raked clean of mortar. If this occurs, water flow out of the detail is dammed up. In other cases, the bed joint of mortar is left in place because raking it out is not architecturally appealing as it breaks the coursing lines of the bed joint (Figure 5).

The introduction of rainscreen drainage planes have improved the predictability of masonry veneer walls.

The introduction of rainscreen drainage planes have improved the predictability of masonry veneer walls.

It is critically important the cavity or core (the void behind the veneer) is open and clear of obstruction to allow liquid water to move from a high point of entry to the lowest point of the cavity or core, which is the top surface of the flashing. In the past, attempts to produce this part of a masonry veneer wall have been the responsibility of masons. The results have varied from good, open, clean cavities to those bordering on being poured solid. Predictable, high-quality results are required to effectively manage moisture. The introduction of rainscreen drainage planes to maintain this void has improved the required predictability (Figure 6).

Detailing the solution: a case study
Proper moisture management for masonry assemblies involves more than just knowledge of weeps. In devising the best approach, dividing the envelope into ‘risk zones’ is crucial. These ‘separations’ are determined by factors such as the building site and climate, the structure itself (i.e. multistory versus low and sprawling), and the materials specified for the envelope. Ranging in intensity from very low to extremely high, the zones are specific sections of the exterior building with unique exposures to moisture. There are many examples of premature failure of the exterior building envelope illustrating entrapped moisture has migrated from one location (zone) to another. This migration, along with the costs associated with premature failure, can be prevented with the appropriate detailing.

The process of determining moisture management zones begins at any part of the exterior envelope. In most cases, since moisture moves from a high point of entry to a low point in the exterior building envelope, starting at the top makes sense.3

A sample building highlighting moisture management risk zones.

A sample building highlighting moisture management risk zones.

A detail of a parapet wall.

A detail of a parapet wall.

In some cases, the process is two steps: first, a determination of a ‘general’ risk zone, followed by a second determination of ‘associated zones’ within (e.g. parapet walls and window openings). Figure 7 is an example of assessing moisture management risk zones for the purpose of designing the appropriate flashing and weep detail to help modify the moisture management risk. They include:

  • parapet wall (Zone 1);
  • decorative cornice belt (Zone 2);
  • window openings (Zone 3);
  • louver openings (Zone 4);
  • door openings (Zone 5);
  • intersection of non-frost-affected concrete stoop and masonry wall (Zone 7);
  • intersection at grade of masonry wall and frost affected sidewalk (Zone 10); and
  • intersection at grade of a masonry wall and landscaping (Zone 11).

Parapet
Zone 1 (Figure 8,) is an example of a parapet wall with multiple associated moisture management details:

  • coping;
  • roof flashing and counter flashing; and
  • transition point from bottom of parapet wall to top of exterior building envelope that encloses the interior spaces—the ‘decorative stone cornice band.’

The coping on the parapet wall is the roof of the parapet and must be waterproofed (Figure 9). One of numerous exterior building envelope details with many responsibilities, coping stones are frequently positioned out of sight. The intersection of the roof and bottom back side of the parapet is another moisture management detail with numerous roles. The roof flashing and the parapet wall counter flashing must be designed to be both waterproof and movement-absorbing; they must be able to accommodate expansion and contraction of the roof assembly.

Decorative cornice
The point where the bottom of the parapet wall ends, and the top of the exterior building envelope enclosing the interior begins, is sometimes unclear. Zone 2 is the top of the decorative stone cornice band (Figure 10). One should not be misled by the term ‘decorative;’ it is also a moisture-diverting detail and a ‘roof’ for the wall and windows below it.

Detail of coping stone.

Detail of coping stone.

Detail of a decorative cornice.

Detail of a decorative cornice.

While attractive, this stone has many open areas that trap snow and moisture and allow it to build up and hold. The flat window ledge also traps and holds moisture.

While attractive, this stone has many open areas that trap snow and moisture and allow it to build up and hold. The flat window ledge also traps and holds moisture.

There is a misconception patterns on the exterior of the building envelope veneers (e.g. stucco, wood, brick, or stone) are simply decorative. In truth, their primary function is protection. They direct moisture away from sensitive details, such as windows and doors. In the past, the construction industry understood this multipurpose concept and had the sense to make them both functional and aesthetically appealing. The current trend seems to concentrate solely on the aesthetic aspect. The unintended consequence of this singular focus is the creation of surface patterns (or details) that actually cause moisture management problems (Figure 11).

Window flashing
Zone 3 is the group of six windows on the second and first floors on the right and left sides of the exterior building envelope (Figure 12). In many cases windows or numbers of windows should be grouped into a single risk zone because their moisture management details are so interconnected and interdependent.

Louvers and windows
Zone 4 is the pair of louvers and windows on each side of the entryway (Figure 13). Obviously, the two types of openings are different, but the moisture management detail is virtually the same. Further,

their proximity to one another joins them into one, unified moisture management risk zone.

In many circumstances, the wall opening directly above another opening will have an impact on the latter’s detail even though they may be of different types. The explanation is obvious: water runs downhill.

Detail of the window flashing.

Detail of the window flashing.

Louver and window flashing.

Louver and window flashing.

Arch above the door
Zone 5 is the arch above the front entry (Figure 14). The arch is probably the most misunderstood moisture management detail of all the wall-opening details—for example, weeps protruding from the radius of an arch is not a good idea, but it still occurs.

If the weeps installed on the radius were to be functional at all, there would need to be an upturned stop flashing at that point of the arch flashing to stop moisture, and the weep would need to be installed at the bottom of the valley in the flashing. It would also have to have the same elevation in the masonry joint. The skill to execute this type of detail is difficult, if not virtually impossible, to find.

Like many good practices and details in the construction industry, the moisture management detailing for arches has been lost to history. Arches have been in common use since the time of the Romans, and so has the moisture management detailing required for their preservation. Nevertheless, most people today simply pass them off as decoration. The gaping mouths in the heads of animals and gargoyles that serve as column caps supporting arches on ancient and medieval structures are actually the weep exits (holes) for the arches’ moisture management system.

Decorative band stone.

Decorative band stone.

Arch detail.

Arch detail.

Decorative band stone
Zone 6 is the decorative band stone separating the bottom of the first floor exterior building envelope from the garden level exterior building envelope (Figure 15). This veneer detail has many responsibilities, including diverting moisture out, over, and away from the windows and wall below it. This decorative band stone also has an aesthetic appearance aspect.

Intersection of vertical wall and stoop
Zone 7 is the intersection of the vertical wall and the top surface of the non-frost affected stoop platform (Figure 16). This vertical wall veneer surface will be subjected to water splash back from the top surface of the platform of the stoop. Additionally, various types of ice control chemicals (e.g. salts and de-icers) may contaminate it, and snow removal tools (e.g. shovels and scrapers) may contract it. This wall detail needs to be durable, aesthetically pleasing, and backed by a waterproofing system because it is an exterior wall system with an interior living space behind it.

Front stoop steps and stoop platform
Zone 8 is the front stoop steps and platform. The seventh and eighth risk zones are the perfect example of the interdependence of moisture management systems. In the case of the stoop platform and steps, the slope-to-drain of the surfaces and their ability to resist moisture penetration is absolutely critical.

Decorative band stone .

Decorative band stone .

Garden-level window.

Garden-level window.

A detail that will allow for replacement of the stoop platform and steps without major impact on the veneer wall system is the appropriate design (Figure 16). This is an example of how a comprehensive understanding of moisture management risk zones influence the original building design and its detailing to allow for future maintenance, repair, and replacement of the exterior building envelope components with the least amount of interruption to adjoining details.

In this instance, the stoop platform is the construction detail that has the most exposure to moisture. In all likelihood, it will need to be repaired or replaced before the other adjoining details. The band of stone at the bottom of the vertical brick wall should be more durable than the brick. It separates the edges of the top surface of the stoop platform from the brick veneer and diverts water away from the intersection of this moisture sensitive detail.

Bottom of wall
Zone 9 is the set of two garden level windows on each side of the front entryway stoop (Figure 17). Window openings at this elevation on an exterior building envelope have several unique moisture management concerns, including their proximity to grade level and accumulating moisture, along with the potential for splashes.

Details at the bottom of the wall: frost-affected sidewalk and landscape stone.

Details at the bottom of the wall: frost-affected sidewalk and landscape stone.

Designing/detailing the grade surface that adjoins these types of grade-level windows is an important factor that will play out in the daily maintenance and their long-term sustainability. The other obvious concern with windows in this location is security. A damaged window is also not waterproof.

On-grade
Zones 9 and 10 are the two on-grade details that contact the bottom perimeter of the building on each side of the front stoop (Figure 18). The grade surface in the first detail is a frost-affected sidewalk; the grade surface in the second is landscaping stone. These two very different ‘on-grade’ materials need to follow many of the

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same rules of good moisture management:

  1. They both need to maintain good slope-to-drain away from the structure they contact.
  2. Their top surface elevation must not interfere with the drainage weeps of other exterior building envelope components (these risk zones). Further, one must consider their movement up or down in elevation due to expansion or contraction of supporting soils due to the wetting, drying, or freeze-thaw of supporting fill material, or because of expansive soils.
  3. These details can never become attached to the structure they abut. The attachment and potential movement of these details will result in severe damage to the structure and the ‘at-grade’ details.

Conclusion
Understanding weeps and identifying unique moisture management risk zones on and in the exterior building envelope are critical for creating and maintaining a sustainable building. However, while these moisture management risk zones can be identified as separate and unique for the purpose of designing and detailing, they are not and cannot be disconnected from each other when it comes to moisture management.

From top to bottom and from bottom to top, they all interconnect and impact each other. No good wall system can survive a bad roof and no good roof can survive a bad wall system; they support and protect one another. This is what holistic and sustainable is all about—knowing that nothing is separate, all things are connected and nothing stands alone.

Notes
1 This reference comes from the 2006 edition—it is puzzling the reference to weeps was discontinued in the 2009 and 2012 versions of IBC given the importance of moisture management in the exterior building envelope. (back to top)
2 It should be emphasized, however, the ability of masonry cavity airflow to dry out or remove moisture is extremely limited. This airflow should not be expected to effectively remove or alleviate any type of ponding water condition—this should be the job of a well-designed weep system. (back to top)
3 Although this article concentrates on the wall portion of the exterior building envelope, it is important to remember many serious wall moisture management problems are actually caused by roof leaks, both low- and high-sloped. (back to top)

John Koester is the founder and CEO of Masonry Technology Inc. With construction experience dating back almost 40 years, he has been a card-carrying mason and cement-finisher, and for many years operated his own masonry construction business in the Minneapolis-St. Paul area. Koester has extensive background in waterproofing systems in the areas of forensics, design, and installation oversight—both in restoration and complete re-roofing projects. He can be contacted via e-mail at john@mtidry.com.

To read the sidebar, “Weep Now or Weep Later: Of Ropes and Tubes,” click here.

Weep Now or Weep Later: Of Ropes and Tubes

by John H. Koester

One of the first commonly employed weep details was the sash cord or ‘rope’ weep. In some cases, this detail was expanded with sections of the sash cord laid in the cavity and then extended through

the wall, usually at a head joint. In other cases, the sash cord was fastened vertically up the backside of the cavity. In yet other instances, it would be pulled out of the wall, leaving a hole through the head joint or bed joint of mortar.

How and when these sash cord sections were placed or embedded in the bed joint of mortar impacted whether they had any weeping capacity. If they were placed on the flashing and the bed joint of mortar was spread on top, the finished detail looked like Figure A. However, if the bed joint of mortar was spread and the sash cord section was laid or embedded into it, the finished detail looked like Figure B. The theory was the cotton sash cord (or a synthetic one) would ‘wick’ water out of the core or cavity and dry the units. However, if there is one takeaway from this article, let it be that one should not get into a wicking contest with mortar or masonry units—how can a 9.5-mm (3/8-in.) diameter sash cord compete against an entire masonry assembly?

Many have seen an example of a rope weep that has moisture stains around the outside end of the cord; it appears to have moisture ‘weeping’ from it. What is really happening is a small amount of moisture is actually exiting the cavity through small voids in the bed joint of mortar at the 5 o’clock and 7 o’clock positions on the bottom radius of the sash cord.

Various tube weeps—pieces of plastic pipe cut to length—have also been introduced to the masonry industry. Their installation procedure is virtually the same as the sash cord material and so are the shortcomings. Even when the tubes are correctly installed on the flashing’s surface, the weep’s wall thickness is still a water dam.

All images courtesy Masonry Technology Inc.

Image courtesy Masonry Technology Inc.

To read the full article, “Weep Now or Weep Later: Moisture management and risk zones for masonry,” click here.

 

Troubleshooting Exterior Masonry Walls

Photo © BigStockPhoto/Ronald Hudson

Photo © BigStockPhoto/Ronald Hudson

by Michael Gurevich

In a sense, all buildings are alive, and they mainly breathe and move through their exterior walls. If a design/construction professional tries to restrain breathing or movements of the exterior walls, then side effects should be expected. Therefore, when a new building is designed and constructed, the brick veneer expansion joints should be provided to accommodate the movement in the brick veneer.

Volume Changes: Analysis and Effects of Movement, and 18A, Accommodating Expansion of Brickwork, with recommendations for the brick veneer wall system. It advises vertical expansion joints in the brick veneer be located approximately 7.6 m (25 ft) apart in addition to the joints at each side of the exterior corner within 1.5 m (5 ft) from the corner.1

Clay brick veneer of the masonry walls normally would have a moisture expansion and a thermal expansion/contraction, which should be absorbed by the brick veneer expansion joints. For example, the moisture expansion of a 12-m (40-ft) long or high brick veneer panel could be calculated with the BIA formula:

0.0005 x L
= 0.0005 x 40 ft x 12 in.
= approximately 6.4 mm (1/4 in.).

The moisture expansion behavior of the clay brick primarily depends on the raw materials and secondarily on the firing temperatures. Additionally, the clay brick’s moisture expansion is an irreversible process with most expansion taking place during the first months of manufacture, but expansion will continue at a much lower rate for several years.

A vertical crack developed in the brick veneer in the middle of this large, first-floor window. It began at the window head shelf angle as a wide, open crack, and disappears into a hairline above.

A vertical crack developed in the brick veneer in the middle of this large, first-floor window. It began at the window head shelf angle as a wide, open crack, and disappears into a hairline above. Photos courtesy New York City Brickwork Design Center

Dealing with cracks
In this hypothetical example, crack development in the brick veneer was the evidence the expansion joints were not adequately provided to absorb the brick veneer movements. For example, with restoration projects of exterior masonry walls, some design professionals are trying to cut vertical expansion joints in 30-year-old brick veneer at 7.6 m (25 ft) apart with additional joints at each side of the corner. However, the problem is the moisture expansion in this brick veneer happened some three decades ago, and Mother Nature has provided the brick veneer with cracks (i.e. natural expansion joints). In other words, the cracks can be replaced with expansion joints, but one should not cut them at 7.6 m apart. (The aforementioned BIA recommendations are mainly for new construction.)

American Concrete Institute (ACI) 530/American Society of Civil Engineers (ASCE) 5/The Masonry Society (TMS) 402, Building Code Requirements for Masonry Structures, has been adopted into the International Building Code (IBC). Chapter 6, “Anchored Veneer,” of the standard has the following requirements for brick veneer:

The horizontally spanning element supporting the masonry veneer shall be designed so that deflection due to dead plus live loads does not exceed L/600.

In Figure 1, a vertical crack had developed in the brick veneer in the middle of the large first-floor window. It started at the window head shelf angle as a wide, open crack, and had disappeared as a hairline crack above. This serves as a perfect example of the spandrel beam excessive deflection, which was translated into the brick veneer as the vertical crack.

The problem is this building was designed in the early 1980s, when spandrel beam deflection had limits of L/360. To fix this problem, one must reinforce the spandrel beam, which would be an expensive proposition. Another option would be to treat the crack as a movement joint, which means to brace the brick veneer on each side with masonry restoration anchors before sealing the fissure.

Another option would be to reinforce the brick veneer with helical stainless steel rods—a technique popular in the United Kingdom with landmark building renovations. Horizontal mortar joints should be raked for a minimum depth of 25 mm (1 in.), and be extended for approximately 406 mm (16 in.) on each side of the crack. The rods should be embedded into the raked joint with a soft grout; they should be located every three to six brick courses apart to reinforce the veneer.

Other examples
In Figure 2, one can see the horizontal crack in the parapet brick wall mortar joints at the roof level with approximately 6.4 to 9.5-mm (¼ to 3/8-in.) vertical displacement in the crack. In this case, the author observed a vertical crack, which started as a hairline at the horizontal crack location, and was wide open at the top of the parapet wall. It looks as if some forces had pushed brick up from the horizontal crack location to the top of the wall. Rust had most likely developed at the top of the steel spandrel beam.

This horizontal crack in the parapet brick wall mortar joints at the roof level resulted in approximately 6.4 to 9.5-mm (¼ to 3/8-in.) vertical displacement.

This horizontal crack in the parapet brick wall mortar joints at the roof level resulted in approximately 6.4 to 9.5-mm (¼ to 3/8-in.) vertical displacement.

This author’s team opened the wall to expose the top of the steel beam, and observed the rust—which had delaminated and expanded up to 9.5 mm—built up atop the beam. Steel beam rust could expand up to 10 times, creating tremendous forces, which pushed the masonry wall up—this created horizontal and vertical cracks in the masonry walls.

This is not, it must be made clear, a ‘masonry wall problem.’ When this building was constructed in the 1920s, no waterproofing was installed at the spandrel beam. Today, one must remove the masonry wall to expose the steel beam for the structural engineer’s evaluation and reinforcement (when necessary). Then, the masonry wall needs to be rebuilt with the steel beam waterproofing and a drainage system installation.

A similar problem can be seen in Figure 3. Multiple cracks had developed at the brick parapet wall located at the exterior corner. Cracked masonry was removed from the wall, and this author observed badly rusted steel beams. About 3.2 mm (1/8 in.) was lost from the steel beam web, given rust expanded eight times. It means rust had expanded for 25 mm (1 in.) and then forced masonry up or out for another 25 mm, developing multiple cracks in the masonry walls.

Multiple cracks had developed at the brick parapet wall located at the exterior corner. Cracked masonry was removed from the wall; badly rusted steel beams were observed.

Multiple cracks had developed at the brick parapet wall located at the exterior corner. Cracked masonry was removed from the wall; badly rusted steel beams were observed.

In Figure 4, one can see a building partially one and two stories. The photo is looking at the ‘low roof,’ toward the brick veneer exterior corner. A vertical crack had developed in the brick veneer at the corner’s roof side, which was located approximately 102 mm (4 in.) from the corner. This author observed vertical displacement of approximately 4.8 mm (3/16 in.) at this crack.

The problem is the brick veneer located at the roof side of the corner was supported by the roof spandrel beam and did not move. The brick veneer facing the street was supported by foundation 5.5 m (18 ft) below. When the brick veneer facing the street had reached the low roof level, it had irreversible moisture expansion and the thermal expansion, which shifted this part of the brick veneer from foundation up to the low roof level for approximately 4.8 mm.

Differential movement of the brick veneer supported by various elements at the different levels had caused this crack. What is the remedy? This vertical crack could be treated as an expansion joint. Brick veneer on each side of the crack became unbraced, and should be anchored to the wall backup system with masonry restoration ties located within 203 mm (8

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in.) from the crack on each side of the crack. The crack should be cut straight, and filled with backer rod and sealant.

A vertical crack had developed in the brick veneer at this corner’s roof side. Vertical displacement of approximately 4.8 mm (3/16 in.) was noted at this crack.

A vertical crack had developed in the brick veneer at this corner’s roof side. Vertical displacement of approximately 4.8 mm (3/16 in.) was noted at this crack.

The low roof parapet had a vertical expansion joint located between the end of the parapet wall and the brick veneer facing the roof. It was the proper location of the vertical expansion joint, but the author observed the end of the parapet wall had leaned toward the roof with the horizontal displacement of approximately 19 mm (¾ in.) from the brick veneer facing the street.

The problem was the end of the parapet wall became unbraced at the vertical expansion joint, and the brick veneer facing the street had expanded up from the foundation 5.5 m (18 ft) below toward the top of the parapet wall. This caused the unbraced end of the parapet wall shifting towards the roof.

The original design/construction should be providing the vertical rebar in the parapet wall backup system to reinforce the unbraced end of the parapet wall. The structural engineer should evaluate this problem; he or she will call for the parapet wall reinforcement if necessary.

Conclusion
For new projects with brick veneer cavity wall systems, architects and engineers should provide the vertical and horizontal expansion joints following the BIA recommendations. Before beginning the exterior wall assembly, design/construction professionals should call for a preconstruction meeting to verify locations and size of brick veneer expansion joints.

Existing building cracks in brick masonry walls should go through the process of design/construction evaluation and diagnostics. Proper rehabilitation techniques must be employed to replace cracks with the expansion joints. After all, it is important to remember expansion joints are essentially just ‘pre-cracking’ the veneer in the proper locations.

Notes
1 Visit www.gobrick.com/Technical-Notes. (back to top)

Michael Gurevich is a masonry consultant at the New York City Brickwork Design Center (NYCBDC), which conducts free seminars on a variety of topics—such as brick veneer metal stud backup exterior walls—for CSI and American Institute of Architects (AIA) chapters. He has 25 years of experience working with exterior masonry walls. Gurevich holds a master’s degree in structural engineering from Belarussian State Polytech University in Minsk. He can be contacted via e-mail at nycbdc@aol.com.

Exploring Mica Coatings’ Potential: A look at Port Canaveral’s Exploration Tower

Photo (c) Rip Noel, Noel Studios Inc. Photo courtesy Valspar Corp.

Photo © Rip Noel, Noel Studios Inc. Photo courtesy Valspar Corp.

by Tammy Schroeder

With its shimmering, iridescent exterior, Exploration Tower at Florida’s Port Canaveral beckons visitors to one of the world’s busiest cruise hubs with its unique appearance as its color changes in different light and at different angles. Opened in November 2013, this soon-to-be-iconic welcome center showcases the first use of a new type of mica coating on the building’s exterior metal cladding.

An integral part of Florida’s Space Coast and Canaveral Cove’s revitalization, Exploration Tower is owned by Canaveral Port Authority. Its opening coincided with the Port’s 60th anniversary of its establishment, and the 500th anniversary of Ponce de Leon’s landing on Florida’s east coast.

Taking its cues from the shapes and hues of the port, GWWO Inc./Architects designed the $23-million, seven-story, sail-shaped structure to express the common characteristics of “transience, function, and imagery.” (Other members of the design team included AECOM [master planning] and Thornton Tomasetti [structural engineering].) The building’s southern elevation soars from the water to the sky. It narrows in scale and reduces its exterior coverage until only the steel frame remains to outline the curvature and comes together at a peak of 18.3 m (60 ft) above the main roof level.

Skanska USA served as the general contractor of the 2137-m2 (23,000-sf) project. The subcontractor responsible for the exterior metal façades and wall system, Kenpat USA, worked closely with the manufacturer that engineered and fabricated the aluminum panels. Another firm provided both the curved structural framing and the 3-D building information modeling (BIM) to coordinate the connection points for each panel in the building’s parabolic curve. In total, Kenpat installed 42 pre-fabricated structural panelized units as sub-structure for the cladding, with the largest being 11 x 3.1 m (36 x10 ft).

According to the architects, the building’s form—sun louvers, exposed structure, and iridescent skin—contribute to a constant sense of movement as the sun plays across the structure. It also meets functional needs, and evokes imagery of Port Canaveral and surrounding Brevard County: a rocket ready to launch, a surfboard in the sand, a ship’s hull, and a rocket contrail.

Canaveral Port Authority’s senior director of construction and infrastructure, David Perley, AIC/CPE, elaborated.

“The Port Canaveral Team, along with our designer, GWWO, wanted a building with a finish that reflects the transient nature of the Port,” he said. “Everything here at the Port is constantly changing—what better way to express change than through the finish of our new Exploration Tower?”

Choosing the coatings
GWWO selected a custom color-changing paint to capture the themes of revitalization and change it sought to represent the Port Canaveral area. Spray-applied to metal wall panels, the coating uses mica flakes to create a consistent, iridescent look. It employs a blend of ceramic and inorganic pigments for its ‘rich’ look.

The southern elevation of Exploration Tower’s sail-shaped structure soars from the water to the sky. Its metal wall panels were finished in a new type of ‘color-changing’ paint. Photos courtesy Kenpat USA

The southern elevation of Exploration Tower’s sail-shaped structure soars from the water to the sky. Its metal wall panels were finished in a new type of ‘color-changing’ paint. Photos courtesy Kenpat USA

The color-changing quality is caused by the way visible light reflects off the mica flakes. The reflective property of the mica flakes means the painted surface will look differently depending on the viewing angle, and the intensity and angle of the light source (e.g. the sun).

Along with its unique appearance, the finish must withstand Florida’s hurricane wind speeds, unrelenting sun, and salt spray. The color-changing mica coating offers the same protection as other 70 percent polyvinylidene fluoride (PVDF) high-performance, resin-based architectural coatings (explored later in this article).

The 70 percent PVDF coating for Exploration Tower’s exterior wall panels was applied as a three-coat system consisting of a primer, basecoat, and color coat. A clear coat was also applied over top for enhanced durability.

As this coating system was new, there was some trial and error during the application process. It was critical each paint run maintain the same parameters, so the spray conditions, paint preparation, and application conformity were all extremely important. The slightest change could alter the final look.

To ensure consistency and minimize variation, the finisher for Port Exploration Tower’s metal cladding and curtain wall assemblies modified its existing paint protocol process. The amount of paint needed for the entire project was determined and ordered as a single batch at the beginning of the project. The special mica technology was prepared all at one time with excellent consistency, taking out the variable of multiple paint batches. The entire project was painted in four phases, starting in March 2013 and ending in May.

In addition to the color-changing mica finish on southern seaside elevation, a 70 percent PVDF white coating was also applied to the northern elevation’s aluminum-framed—and hurricane-rated—curtain wall that offered views of the bustling port.

As with other 70 percent PVDF coatings, the white and color-changing mica paints used on Exploration Tower meet the most stringent, exterior, architectural standard: American Architectural Manufacturers Association (AAMA) 2605, Voluntary Specification for Performance Requirements and Test Procedures for Superior Performing Organic Coatings on Aluminum Extrusions and Panels. This specification requires paint coatings to meet rigorous testing performance standards, including heat- and humidity-resistance and more than 2000 hours of cyclic corrosion per Annex 5 of ASTM G85, Standard Practice for Modified Salt Spray (Fog) Testing. Per AAMA 2605, the coating also must maintain its film integrity, color retention, chalk resistance, gloss retention, and erosion resistance properties for a minimum of 10 years on the South Florida testing site.

Coatings selection
Whether the project is a landmark in Port Canaveral or a more typical office building, specifying paints for architectural aluminum products requires careful consideration. It is important to remember to review performance strengths and limitations, composition and sustainability, specification standards, warranty, and maintenance practices with respect to the project’s unique application, location, and function.

This chart summarizes paint standards published by the American Architectural Manufacturers Association (AAMA).

This chart summarizes paint standards published by the American Architectural Manufacturers Association (AAMA).

Architects and building owners should determine which performance specification is required, along with the paint color. In order to ensure the paint performance expected for a given application, one of three standards should be referenced:

  • AAMA 2603, Voluntary Specification for Performance Requirements and Test Procedures for Pigmented Organic Coatings on Aluminum Extrusions and Panels;
  • AAMA 2604, Voluntary Specification for Performance Requirements and Test Procedures for High-performance Organic Coatings on Aluminum Extrusions and Panels; or
  • AAMA 2605—the one used for the Port Canaveral project.

These three specifications apply to progressively stronger levels as indicated by South Florida outdoor exposure and laboratory accelerated testing results as shown in Figure 1.

Strengths and limitations
A particular coating’s strengths can come down to several variables. Some include:

  • color retention (i.e. ultraviolet [UV] resistance)—AAMA 2605 specifies that paints show no more than 5∆E color-fade in 10 years of exposure;
  • salt-spray resistance—AAMA 2605 specifies paints resist up to 4000 hours of accelerated salt spray testing;
  • vast array of color choices;
  • protects and maintains the aluminum’s structural integrity;1
  • field touchup/repainting capabilities; and
  • small-batch and custom color capabilities that allow maintenance to be fast and cost-effective.

Possible limitations to consider include:

  • fair hardness;2
  • cost of high-performance products (pricing typically increases with stringency and weathering performance—in other words, paints specified to meet AAMA 2603 tend to be less costly than those to meet AAMA 2605); and
  • potential for inconsistent appearance of ‘metallic’ paints.

Further to this last point, a consistent, random orientation of metallic and mica flakes produces uniform color and brightness. To achieve perfectly random flake orientation, many variables need to be managed in a spray-application process. These variables include:

  • different part geometries;
  • electrostatic/grounding effects;
  • fluid pressures;
  • paint-to-part distances;
  • overlapping spray areas; and
  • supplemental hand-spray to reach recessed or corner areas.

Solvent-based paints may not be considered environmentally sustainable without an oxidizer. The primary environmental concern with liquid paints is the solvents used to deliver the paint to the part; some of the solvents used are considered volatile organic compound (VOC) content and must be destroyed. VOC content, when released directly into the atmosphere, has been known as a contributor to ozone depletion. However, environmentally conscious finishers use a 100 percent air-capture system and destroy the VOCs with a regenerative thermal oxidizer, so there is no adverse environmental impact.

Composition
The exact composition of a particular paint coating often is complex and proprietary. In general, paints contain resins, pigments, reducers, and additives. A typical gallon of paint is 10 percent pigment, 20 percent resin, and 70 percent solvent (i.e. reducers and additives).

Capturing themes of revitalization and movement, Exploration Tower at Port Canaveral incorporates sun louvers, a partially exposed structure, and iridescent skin.

Capturing themes of revitalization and movement, Exploration Tower at Port Canaveral incorporates sun louvers, a partially exposed structure, and iridescent skin.

Resins are the compounds in the paint that form the film and hold the pigment in place. The resin system incorporated into the paint is the determining factor in the specific characteristics and performance properties. In the architectural industry, two primary resin systems are involved in refinishing of metals: fluoropolymer-based (i.e. the aforementioned PVDF) or ‘baked enamel’ type, which is usually composed of acrylic or polyester resins. It is not uncommon for a coating to contain several resins, which help the coating perform to specific requirements.

Pigments are the material added to the paint to give it color, or to enhance certain physical properties of the coating. These are selected based on physical needs, durability, gloss, colorfastness, and chemical exposure. Pigments are both naturally occurring, as well as synthetic.

Reducers are used to serve different purposes. Using an active solvent reduces the viscosity, allowing the coating to be sprayed. Once on the substrate, the solvent evaporates and leaves the painted film. Volatile components can be solvents, waterborne (i.e. water-based and water-reducible), and 100 percent solids. Diluent solvent is used to extend a solution, but weakens the active solvent’s power. Thinner solvent can extend a solution, but does not impair the power of the active solvent.

Additives and fillers, meanwhile, are usually individualized to paint type and specification. These are used in small amounts to thicken the paint. They also can provide a wide range of modifications to the composition of the film and the film properties, such as enhancing gloss and hardness. Other characteristics may include improving flow properties, finish, or paint stability to UV exposure. Further, they can provide a non-stick surface to the paint film or anti-graffiti capabilities.

After the paint is applied, different types of curing systems include air dry, air dry/force dry, bake/cure, catalyzed, and radiation.

Warranty explanations
For aluminum coatings, the design professional should carefully review warranty explanations offered by the paint manufacturer and finisher. For example, if adhesion is going to fail, it will typically fail in the first year of its service life, and the warranty will cover the issue. When the adhesion is good from the start, it rarely fails during the service life of the finish.

It is also important to remember ‘gloss’ is the reflectance of the paint or anodize finish, and is measured on a scale from 0 to 100 units. ‘Zero’ gloss is completely flat, absorbing all light, while 100 gloss reflects all light back. All finishes will lose gloss over time, but some will lose faster than others.

Chalk is a ‘breakdown,’ typically caused by intense UV rays, of the resin system of the paint itself. Chalk occurs when conditions cause degradation of the resin system, as the resin breaks down it takes on a whitish, chalky appearance.

The leaching or oxidizing of pigment is known as ‘fade.’ Like chalking, fading also is caused by intense UV radiation. All pigments will fade over time, but the degree to which they fade depends on several properties. Aluminum finishes that have a high resistance to fading have a low Delta E reading.

Unless a particular project is in an extreme environment, one should expect a high-quality, high-performance finish to last several years beyond, and in some cases multiples of, the warranty period.

However, it is important to remember paint manufacturers and finishers do not have control of maintenance, location, or use. For this reason, warranties cannot be issued beyond a ‘guaranteed service-life’ timeframe in the most extreme environments.

Exploration Tower’s northern elevation features a hurricane-rated, aluminum-framed curtain wall.

Exploration Tower’s northern elevation features a hurricane-rated, aluminum-framed curtain wall.

Maintenance
To maintain the original beauty of finished architectural aluminum products, occasional cleaning is required on even the most highly durable finishes. One should select mild soap solutions that are safe for use with bare hands, such as those products typically employed to wash a car. Strong acid or alkali cleaners could damage the finish, as can abrasive materials such as steel wool or brushes.

Solvents no stronger than mineral spirits or denatured alcohol may be used to remove grease, sealants, or other materials. Cleaners or solvents should never be combined, as the resultant mixture can cause harmful or even dangerous results. Once heavy soil, grease, or sealant is removed, the mild soap solution should be applied with a soft cloth, sponge, or soft brush. The surface must be thoroughly rinsed with clean water and dried with a soft cloth. In coastal areas (where the finish is exposed to salt spray), or in locations containing heavy industrial pollutants, the cleaning should take place on a regular basis.

Conclusion
Specifying unique finishes for architectural aluminum products in harsh climates can be done with confidence when working in close collaboration with manufacturers and finishers to achieve the performance requirements and the desired, dynamic appearance. Exploration Tower at Florida’s Port Canaveral serves as a striking, color-changing case in point.

Notes
1 With its inherent corrosion resistance, aluminum’s ability to maintain structural integrity is well-documented. High-performance paint enhances this durability and aesthetic, extending the lifespan of these products. (back to top)
2 Also known as ‘pencil hardness,’ this correlates to abrasion resistance of the dry finish. AAMA specifications refer to ASTM D3363, Standard Test Method for Film Hardness by Pencil Test. The harder a finish, the more resistant it is to scratches and abrasions. Anodize Class I finishes have excellent hardness. (back to top)

Tammy Schroeder, LEED Green Associate, is a senior marketing specialist at Linetec. She has more than a decade of experience working with architectural aluminum products and finishes. She also develops the company’s American Institute of Architects/Continuing Education System (AIA/CES) programs, and serves on the American Architectural Manufacturers Association’s (AAMA’s) Tactical Marketing Plan Group and Value Proposition Work Group committees. She can be reached at tammy@linetec.com.