DRAINABLE WRAP INSTALLATION BEST PRACTICES

Images courtesy of TAMLYN

The Issue: Sometimes a great product doesn’t perform as it should because it isn’t installed in the building properly.

The Solution: Following best practices as determined by product manufacturers or building science specialists can help assure that the intended performance is achieved. Architects or envelope commissioning agents making on-site inspections should be aware of the following best-practice recommendations when drainable building wrap is installed.

Installation Process: Drainable building wrap should always be lapped in shingle fashion starting from the lowest point. This means that it is installed first from the bottom of the wall and the installers work their way up the wall. In this way, the required proper shingling of wrap layers allows the installed system to shed water to prevent water from entering the wall system. Further, when using drainable wrap as the primary air barrier, tape all seams using seam tape, always ensuring that the seam area is dry and clean. It is recommended that for best adhesion a hard roller or hand applicator is used.

With the above in mind, these are the typical, preferred installation steps.

• Unroll the drainable wrap with the spacers facing to the exterior.
• Drainable wrap should be installed shingle-lap fashion (i.e., begin installation at the base of the wall assembly).
• Extend the drainable wrap a minimum of 2 inches over the sill plate.
• Fasten the first course of drainable wrap to the sheathing using cap- fasteners.
• Seam tape is applied to the first course by removing one side of the release paper and, for best results, is laid down using a hard roller or hand applicator.
• With the first course in place, unroll the next course of drainable wrap maintaining the required overlaps with fastening stopping 9 inches from the bottom of this course, allowing for it to be folded up.
• Overlap all horizontal seams by at least 6 inches, all vertical seams by at least 6 inches, and corners by 12 inches.
• Fold the upper layer of the drainable wrap up and remove the release paper on the seam tape, then press the layers together using a hard roller or hand applicator. Then complete fastening along the seam.
• Continue the process above until the entire wall is properly covered.

There are also some general installation best practices to be aware of:

• Use only commonly available scissors to cut drainable wrap since the use of a utility knife will break the bond of the filaments (spacers).
• Fasteners should provide a minimum ½-inch penetration into the nail base and be spaced approximately 12 to 18 inches apart along the horizontal and vertical laps through seam tape. Fasten every 3 square feet everywhere else.
• Assure that the drainable wrap installation and flashing provide for positive drainage to the exterior of the assembly.
• Do not allow the drainable wrap to be exposed to sunlight in excess of 120 days. In fact, it is recommended that it be covered within 30 days.

The above practices apply to the solid wall areas where drainable wrap is being used. For windows, doors, and other openings, consult manufacturer-recommended procedures for sealing and flashing around all of these building components.