The purpose of the design professional’s instruments of service (drawings and specifications) is to convey design intent. Their exterior enclosure designs are intended to perform under anticipated natural and potential man-made conditions. Building codes and industry standards establish specific performance requirements for the exterior enclosure, including structural loading, weather protection (wind-driven rain), fire resistance, acoustical separation, thermal resistance, and others. With all this effort to consider the holistic impact of both environmental and man-made conditions that may be exerted upon the exterior enclosure, why do we see so many water-intrusionrelated deficiencies in mid-rise wood frame construction? While there is significant effort spent in conveying design intent, far less effort seems to be spent in ensuring our designs will actually perform to the standards we often cite in our construction documents. As architects and building enclosure consultants, we have investigated numerous water-intrusion-related deficiencies in mid-rise wood frame buildings and developed checklists and report formats based on project type, needs of the client, and project conditions. These checklists are derived from building codes, industry standards, and personal experience. For example, the recommended format for property condition assessments is ASTM E2018, Standard Guide for Property Condition Assessments, and property maintenance reviews are typically based on the International Property Maintenance Code. Regardless of the type of building enclosure consulting services being provided, we have observed that mid-rise wood frame construction tends to experience similar problems with regard to water intrusion. This article will provide an overview of the most common water-intrusion-related deficiencies observed within the building enclosure on these types of projects. ORGANIZATION OF BUILDING INFORMATION There are several well-recognized organizational structures for building information used in building evaluation reports. We have found that unless otherwise required, we prefer to use a customized organizational logic based on building elements as published in UniFormat, A Uniform Classification of Construction Systems and Assemblies by the Construction Specifications Institute (CSI) and Construction Specifications Canada (CSC). This structure is commonly used for arranging cost information, preliminary project descriptions, performance- based project manuals, building information modeling (BIM) object libraries, facility management information, and other applications. As such, it is well understood 1 8 • I I B E C I n t e r f a ce Oc t obe r 2 0 1 9 Figure 1 – Exterior corner sheathing fasteners failed to be fully anchored into the stud framing. by owners, designers, contractors, building product manufacturers, and most users of building information. For the purpose of addressing building enclosure weather protection problems in this article, we have grouped the design and construction problems into two primary building elements: exterior vertical construction and exterior horizontal construction. Elements are divided into sub-elements, and specific construction-related problems are addressed under the sub-element. EXTERIOR VERTICAL CONSTRUCTION Exterior Cladding Exterior cladding provides the initial rain-screening function for the exterior vertical building enclosure. There are many types of exterior cladding (e.g., anchored masonry, adhered masonry, stucco, and fiber-cement siding, to name a few), and many construction-related problems can be specific to each type of product. There are also common problems, regardless of cladding type. Below is a discussion of these common problems. Cladding Attachment Most building codes and building product manufacturers have attachment requirements for the exterior cladding based on material type, building height, and wind velocity. We often see problems in exterior cladding with missing fasteners, fasteners not anchored in structural framing, incorrect spacing of fasteners, and incorrect type of fasteners. Attachment requirements are typically established by either prescriptive or reference standard methods. Designers need to clearly understand the code requirements for cladding attachment and convey the design intent in their construction documents (Figure 1). Drainage One of the most common problems we experience is the failure to provide adequate drainage of moisture from behind the exterior cladding. Whether a drainage cavity wall or a drainage plane wall, designers and contractors must ensure that an open pathway exists with properly integrated flashing and weeps to allow for moisture drainage. We strongly recommend rain screen walls with cladding attached to furring strips or a drainage mesh material behind the exterior cladding. This is the most effective method to avoiding entrapped moisture behind the cladding that negatively impacts the water-resistive barrier (WRB) and the underlying structural elements. Expansion Control All materials have a coefficient of thermal expansion and will expand and contract with changes in temperature. Also, some materials expand and contract with changes in moisture, due to drying (shrinkage) and absorption (expansion). Building design and documentation must take into consideration the need for expansion control and the proper location and spacing of expansion and control joints. Consideration must also be made for the differential movement of dissimilar materials. Codes and reference standards often provide not only spacing requirements but also maximum ratios for joints and joint size. Failure to properly design and install expansion control may result in the premature failure of joints and expansion devices, which can lead to water intrusion into the building. If the wood frame structure is to be clad with brick, the expansion of the brick in direct opposition to the shrinkage of the wood framing must be carefully considered to avoid damage and cladding failure (Figure 2). Openings Building openings include doors, windows, skylights, louvers, vents, and basically anywhere the vertical plane of the exterior enclosure is interrupted or penetrated. We have found wall openings to be one of the most common locations for water intrusion in buildings; therefore, we typically start our investigations at these locations. In addition to the window, sheathing, and WRB installation problems, failure to properly install exterior cladding drainage can first appear at windows. Below are a few of the most common problems we see at window openings. Window Installation Windows are typically nailing-fin or flange type, which is most commonly utilized in wood-frame, or flush-fin type, which is most commonly used in CMU construction. There are three primary treatments of rough openings, including the framing itself, the correct installation of the window, and the flashing of the window to the exterior wall. It is imperative that the rough opening is properly tied in to the sheathing and the framing. Each manufacturer of windows and WRBs provides instructions for the correct treatment of the rough opening prior to window installation. In some cases, there may be conflicts between the WRB system manufacturer’s instructions and the window manufacturer’s instructions. These conflicts should be resolved prior to installation. The window installation itself is governed by ASTM E2112, Standard Practice for Installation of Exterior Windows, Doors, and Skylights, as well as the window manufacturer’s instructions. These should be followed closely to ensure the window is installed plumb, level, and square, as alignment issues affect not only the day-to-day operation of the window but its ability to prevent water intrusion to the interior. If the window is not installed to the tolerances outlined in ASTM E2112 and the manufacturer’s installation instructions, then the manufacturer’s warranty is void. Oc t obe r 2 0 1 9 I I B E C I n t e r f a ce • 1 9 Figure 2 – Although the control joint was installed, it was not installed continuously through the entire brick assembly. The final piece of the window installation process is flashing the window to the WRB. Once again, the manufacturers of both the window and the WRB provide installation instructions that need to be coordinated. We recommend that a mock-up of the installation be constructed and tested prior to the full installation process to ensure any issues are resolved up front (Figure 3). Door Installation Doors tend to have issues at the thresholds— primarily in locations where a stepup is either not allowed or not part of the overall design. In a zero-entry condition, the threshold component is exposed to water that is pushed via wind or by sheer volume onto the threshold and typically enters at the jamb-to-threshold detail. Another condition that can lead to interior water intrusion is the installation of in-swinging doors. This condition prevents the door from having a secure back leg seal at the threshold. The installation of a one-piece sill beneath the threshold that end-dams at each side behind the jambs, as well as the installation of out-swinging doors, can prevent a majority of the issues observed at these locations. Issues discussed above with regard to rough opening treatment, door installation, and final flashing to the WRB as discussed in the window installation section above should be taken into consideration as well. Wall Penetrations (Exhaust Vents, Lights, Conduit, etc.) In our building observations, we often see conditions in which the sealing and flashing of penetrations through the building enclosure are not properly made w e a t h e r t i g h t . Typically, these types of penetrations rely only upon sealant at the exterior cladding, and the penetration through the backup wall is largely ignored. In this case, if water gets behind the perimeter sealant at the exterior cladding, it will then stay in the wall cavity, possibly getting behind the WRB and damaging the structure. Penetrations should be treated similarly to window and door openings in that the penetration should be fully flashed to the WRB and then sealed at the perimeter where the projection meets the cladding. Some cladding materials, such as fiber cement board products, require metal flashing and blocking details at projections (Figure 4). WRBs WRBs are generally the last line of defense in the protection of the building enclosure from water intrusion. WRBs include both sheet and fluid-applied products. Our experience is that sheet products are far more susceptible to installation problems. Below are a few of the most common installation problems we see in these types of products. Discontinuity of the WRB Discontinuity of the WRB results in many installation errors, including tears in the WRB, improper lapping, failure to tape seams, failure to completely install the WRB at some locations in the building, and 2 0 • I I B E C I n t e r f a ce Oc t obe r 2 0 1 9 Figure 3 – Improper flashing of the window head to the WRB causing sheathing damage and degradation. Figure 4 – Improper flashing of these dryer vent penetrations caused moisture to penetrate and damage the exterior sheathing below the vent penetrations. the mixing of materials and manufacturers. While it is difficult to pick the single most common installation problem with WRBs, reverse lapping of mechanically fastened sheet WRBs directs moisture behind the WRB and creates the most damage to wood structures. This most commonly occurs at the head flashing of doors and windows, floor lines, and at the base of wall assemblies. In this condition, the installer fastens the flashing material over the WRB as opposed to inserting it under the WRB so that the WRB shingles over it. This prevents the proper functionality and entraps moisture behind the cladding and possibly the WRB itself. Sheathing In addition to traditional sheathing panels, wall sheathing includes a wide range of materials and may be insulated, fireresistant treated, weather-resistant, or have other properties, depending on the facer or treatment. Weather-resistant sheathing panels do not require a separate WRB; however, the panel joints and fasteners must be taped or treated to prevent moisture intrusion. During testing of a magnesium oxide (MgO) sheathing board product, the test sample failed to provide adequate weather protection in accordance with ASTM E331, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference, and exhibited significant water intrusion at panel joints and at fasteners. Other similar products have been shown to absorb moisture and emit magnesium chloride (MgCl2) that can deteriorate cladding fasteners. The sheathing ultimately provides the underlying support structure for the WRB and cladding, and therefore, it is important that it is fastened correctly with proper fasteners and in accordance with local building codes and other standards applicable to the installation. Fasteners Most manufacturers of sheet WRB products require the use of cap nails or screws for the installation of their products. We often see the use of slap staples, which cause tears in the material, rust over time, and create thousands of holes in the WRB. If staples are used to assist the installation of sheet-applied WRBs, they should be used in accordance with the manufacturer’s instructions and must be taped over to prevent the transmission of water through the WRB to the sheathing. As discussed in the previous section, be mindful of the fastener type, as this affects both the structural and fire rating of the wall assembly as a whole (Figure 5). EXTERIOR HORIZONTAL CONSTRUCTION Roofing Roofing systems on mid-rise wood frame construction can be divided into steep-slope and low-slope assemblies. Per code, lowslope assemblies have a minimum of 1/8:12 slope for coal tar built-up roofs and 1/4:12 slope for all other types up to 2:12 slope. Steep-slope roof assemblies are those that have a slope greater than 2:12. Asphalt shingles tend to be the most common type of steep-slope roof covering on mid-rise wood frame construction. Each of the two types of roofs has specific issues that will be discussed below. Steep-Slope Roofing Sheathing The roof sheathing provides the support for the underlayment and the roof covering. If the sheathing is improperly installed, then it will be challenging to install the underlayment and roof covering in a uniform manner. The sheathing should be installed with the appropriate spacing around all four sides to allow for expansion and contraction of the materials during seasonal changes. Failure to do so will cause telegraphing through the underlayment and roof covering that is not aesthetically pleasing and can cause premature failure of the asphalt shingles. Underlayment Discontinuous underlayment is a condition we frequently observe on steep-slope shingle roofs. This is caused either by the installing contractor simply missing areas or by improper or missing perimeter attachment detailing. Wind uplift forces are more significant at the eaves and corners as opposed to the field of steep-slope assemblies due to roof geometry in relation to the walls. Over time, standard felt underlayments that are not fully secured at these locations can be torn, leaving the sheathing exposed. Also, in our experience, a peel-and-stick type of membrane should be utilized at all times at the eaves of the roof, as well as at the valleys. Often, peeland- stick is not utilized at the eaves due to ambiguity in the code language; however, the installation of this material—as opposed to standard felt underlayment—provides protection at this critical location (Figure 6). Oc t obe r 2 0 1 9 I I B E C I n t e r f a ce • 2 1 Figure 5 – WRB in this location was fastened with two button-cap nails while the rest of the fasteners consisted of slap staples. Flashing Flashing installation is critical in steepslope assemblies. Typically, we see the sidewall flashing and chimney flashing installed, but kick-out flashing is often omitted. Kickout flashing is critical where the roofline meets a wall surface that extends beyond the roofline. At these locations, the capillary action of water as it sheds down the roofline will remain in contact with this vertical wall surface, saturating it beyond what it can capably manage. In these cases, internal damage can occur as the wall remains wet over extended periods of time. Kick-out flashing breaks this capillary action and pushes the flow of water toward the perimeter gutters located at the eave. Another typical failure location is where the eave flashing is installed without the proper leg dimension at gutters. This allows water to curl behind the gutter as opposed to being directed into the gutter, damaging the fascia board material. Roof Covering Steep-slope roofs can have coverings of many different types of materials. In our experience, the most common materials are metal or asphalt shingles. Many asphalt shingle issues are related to sheathing and underlayment deficiencies, discussed in the previous sections. Those conditions not related to incorrectly installed sheathing and/or underlayment can be traced to improper fastening patterns, incorrect nailing location, penetrations through the roof covering, and flashing. When anomalies exist in the asphalt shingles, it is common for the fastening pattern and location to be incorrect. Metal roof coverings in steepslope assemblies tend to perform well and typically are mechanically seamed or have snap seams. Problems tend to occur where the structure does not allow for enough slope and where flashing is improperly installed for the condition. Low-Slope Roofing Drainage The number-one way to avoid water intrusion into a structure is to provide adequate drainage capabilities. This is true regardless of whether you are dealing with the roof, the walls, or the perimeter grading. The most common issue that we see is the improper flashing of through-wall scuppers and improper heights at these locations. The scupper heights are dictated by the framing, and a lack of coordination between the framing contractor and the roofing contractor will often cause the area at the scupper to collect water. Scupper locations have numerous seams and, therefore, water intrusion is common. The other issue that arises with regard to drainage is the installation of HVAC, exhaust, and roof hatch curbs in drainage lines. Once again, this causes ponding water behind the curb and can lead to water intrusion (Figure 7). Coping Coping cap installations at perimeter parapet walls are often lacking the appropriate details to prevent water intrusion at these locations. Where a stone coping 2 2 • I I B E C I n t e r f a ce Oc t obe r 2 0 1 9 Figure 6 – Underlayment was not properly fastened at this location, leaving the sheathing exposed. Figure 7 – Voids in the flashing at this scupper location allowed water to penetrate into the interior space below. is installed, the roof membrane is typically terminated just below the stone without a flashing component installed beneath the coping stone. This allows water to roll over the coping stone and get behind the roof membrane. The roof membrane must be secured over the parapet wall in a manner that keeps water from penetrating behind it as water flows over the coping material. Flashing Flashing on low-slope roof systems at curbs and perimeter walls is required to be a minimum of 8 inches in height from the horizontal roof membrane. This prevents water from pushing up against the wall or curb and over the flashing and entering the building. This is most commonly a problem when equipment is installed post construction, such as when an exhaust vent or HVAC system is added after the building is completed. Often, the installing contractor of these secondary systems does not allow for the required flashing height, leading to penetrations that are vulnerable to water intrusion. Balconies Balconies are the most common location for water intrusion problems on mid-rise wood frame buildings. The lack of proper slope and integration of flashing and waterproofing seems to be treated almost as an afterthought in the overall design and construction of the exterior wall assembly. Special attention must to paid to the detailing and installation of T-bars and the underlying drainage plane in concrete balconies. We strongly recommend the use of a drainage mat above the waterproofing and water testing to ensure performance. Waterproofing The order of work for balconies typically means that the waterproofing may be left unprotected for a certain period of time. This can lead to voids in the waterproofing membrane applied to the wood decking or concrete as trades continue working in the area that has been waterproofed. Additionally, handrail stanchions are often installed through the topping slab in a manner that penetrates the underlying waterproofing system (Figure 8). Transitions The transition where the horizontal framing of the balcony meets the vertical framing of the walls often is not properly tied in from a waterproofing standpoint. There is a lack of integration between the horizontal waterproofing and the vertical WRB components. This leads to a scenario where the water may not be penetrating the deck waterproofing or the WRB, but the Oc t obe r 2 0 1 9 I I B E C I n t e r f a ce • 2 3 Figure 8 – Failed waterproofing on this balcony caused severe damage to the structure and underside of the deck surface. Figure 9 – This balcony structure was not properly integrated into the vertical wall assembly, causing constant water intrusion at the location where the balcony meets the vertical wall. space between the two. Another problematic location is where the exterior wall meets the balcony. In these locations, the cladding materials are not properly separated from the balcony structure, leading to water migration from the wall cavity to the balcony structure or vice versa (Figure 9). CONCLUSION Good construction documents are an important tool in achieving a building that performs well, but without verification of compliance with the contract requirements through rigorous construction contract administration and field quality assurance, actual performance of the building is unknown. As the old adage goes, “You get what you inspect, not what you expect.” It is imperative that the building enclosure consultant, engineer, or architect who is responsible for analyzing the performance of existing construction in mid-rise wood frame buildings perform a systematic analysis that moves through the various exterior elements with a fundamental baseline of possible conditions. Quality assurance can only be accomplished through testing and inspections. The list above, while not exhaustive, provides a source for common deficiencies found in our experience in the investigation of these types of structures. This information can assist the professional with the water intrusion investigative process as elements and details are examined and possibly eliminated, until ultimately, the sources of water intrusion and migration throughout the building are determined and a plan for repair and mitigation can be developed and executed. Lonnie S. Coggins is a vice president of HALL|AEC and directs the firm’s field quality assurance team, including testing services. He has more than two decades of experience in providing roof, waterproofing, and building enclosure investigation and consulting services on projects in the U.S. and around the world as a consultant for the U.S. government. Coggins currently serves as vice president of the Carolinas Chapter of IIBEC. Lonnie S. Coggins Dennis J. Hall, FAIA, FCSI, is managing principal of HALL|AEC, headquartered in Charlotte, NC. He has over 40 years of experience as an architect, construction specifier, construction contract administrator, and building enclosure consultant. Hall has a bachelor’s degree in architecture from the University of North Carolina at Charlotte and a master of architecture degree from Washington University in St. Louis. He is a former national president of the Construction Specifications Institute. Dennis J. Hall, FAIA, FCSI 2 4 • I I B E C I n t e r f a ce Oc t obe r 2 0 1 9 New homes built in California after January 1, 2020, must be equipped with a solar electric system. They must be sized to offset 100% of the home’s electricity usage, though homes can still use energy from other sources, such as gas. The size of solar arrays can be reduced if other energy efficiency improvements are made elsewhere, such as inclusion of energy storage or green building materials. The California Energy Commission (CEC) estimates the mandate will add roughly $9,500 to upfront construction costs, but save the homeowner $19,500 over the life of the system. The mandate is part of an initiative by the CEC to have at least 50% of the state’s energy produced from clean energy sources by 2030. New Jersey, Massachusetts, and Washington, D.C., have considered legislation to require new buildings to be solar-ready, but California’s move is the boldest and most consequential to date. This, on top of a shortage of affordable housing, is one of California’s most pressing issues. Image by Alex Csiki from Pixabay. California Solar Energy Mandate Soon in Effect
