Architectural Record BE - Building Enclosure

Detailing Continuity in Building Enclosure Systems

Integrated products and proper detailing help maintain air, water, and thermal barrier integrity
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Sponsored by Huber Engineered Woods, LLC
By Peter J. Arsenault, FAIA, NCARB, LEED AP

Choices in Barrier Systems

As with most design and construction systems, there are choices available in how to achieve each of the four building enclosure barriers and assure their continuity on and around a structural framing system. The conventional approach is to use a multi-product, multilayer solution where each of the four barriers is specified and installed as a separate layer in an assembly. This requires specifying multiple products that need to be compatible and performing multiple labor tasks, perhaps by different trades, during construction, all of which need to be coordinated. Further, to be assured that their installed performance will be met, the particular combination of products needs to have been tested to assure they meet all of the water, air, and thermal thresholds required for the assembly. There also needs to be proper detailing between the materials to assure the total system will work as intended.

As an alternative, there are integrated product solutions that have become available, most notably in the form of integrated sheathing. These products typically come in the form of engineered structural wood sheathing that can also provide at least two of the needed barriers with preapplied coatings that qualify as both a WRB and an air barrier. This means that a single, high-performing wood sheathing product can be specified, used as the basis of design, and installed by a single trade in the building. Such integrated sheathing systems rely on factory-created surfaces on the sheathing that can meet both air and water barrier requirements with a higher assurance of performance since they are installed under controlled conditions. In some cases, they can also include a thermal barrier of continuous insulation of differing thickness preapplied to the sheathing and ready to install. Overall, the installation can be simpler and quicker, reducing the amount of labor and skill needed to create an effective end result.

Of course, such integrated sheathing products need to address the joints, penetrations, and openings, just like any other system, to assure continuity and effectiveness. In this case, that is achieved with compatible self-adhering tape, sealants, and even liquid flashing where appropriate.

construction worker using a roll tape system

Photos courtesy of Huber Engineered Woods, LLC © 2016

A complete roll tape system includes everything needed to seal any gaps or seams for both water and air barriers, including along flashing locations.

The beauty of these components is that they allow for a lot of versatility to accommodate the differing site conditions and design variations that may occur. The flexible nature of the sealing tape and liquid flashing is such that they can conform completely to the shape of the substrate surface to seal and protect the surrounding construction in a truly continuous manner by covering the joints and seams between the pieces of sheathing. This allows for the needed structural gapping in the sheathing but assures that the air and water barrier is fully continuous even with minor expansion and contraction of the sheathing panels.

Other conditions of construction need a little more attention. Small bump-outs or recesses in a wall system should be sheathed with the same integrated sheathing as the flat, continuous sections. Then, the tape can be used to cover all of the irregular shapes and edges of the condition to assure full continuity of the barriers. Penetrations should be treated in the same, with the self-adhering tape covering the entire perimeter of the hole or opening and wrapping the edge of the sheathing. Once the reason for the penetration is installed (i.e., pipe, duct, wire, etc.), then a compatible sealant should be used to fill in completely any remaining gaps.

Window and door openings also require attention. It is important that the barriers continue tightly and seal completely against the window and door frames to avoid gaps and breaches in the air and water barriers. It is also critically important that those windows and doors are properly flashed to avoid any water or air seeping in behind the frames and causing damage. Metal head flashing can be used in these cases, or “self-flashing” clad windows may have the flashing already incorporated. Either way, the place where the flashing meets the integrated sheathing should be covered with self-adhering tape too in order to assure full continuity.

Recessed conditions or areas prone to more severe weather may warrant that the full perimeter of the opening is covered and treated with a continuous, flexible, liquid flashing that will cure to protect the opening and assure continuity of the barriers. Then, a compatible sealant can be used to fill any remaining gaps between the sealed rough opening and the window or door frame.

Construction workers filling in liquid-applied flashing

Photo courtesy of Huber Engineered Woods, LLC © 2017

Liquid-applied flashing can be used to seal surfaces completely even in wet or cold conditions.

 

[ Page 3 of 4 ]       
Originally published in Architectural Record

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