Every year we inspect thousands of homes with one brand or another of housewrap installed as the water-resistive barrier (WRB).
As energy costs increase and energy code requirements become more stringent, we are seeing housewrap installations where the seams are sealed with tape. Many housewrap manufacturers have proprietary seam seal tapes that they sell for exclusive use with their housewrap system.
As implied by the name, the tape is used for sealing the seams of the housewrap. The purpose of sealing the seams is to create a continuous air barrier. Some of the manufacturers imply that the use of their tape will also reduce moisture intrusion.
Horizontal tape is problematic
The installation procedure for housewrap, regardless of the manufacturer, is fairly standard across the board.
Installation begins with a course at the base of the wall and that course is overlapped horizontally with the next course. The amount of the horizontal overlap varies by manufacturer. Additionally, vertical seams must also be overlapped.
If the seams are going to be taped, the work generally occurs after the entire house is wrapped or after several courses of wrap are installed.
The horizontal seam tape is installed by lapping the tape over both layers of wrap. This means that the seam tape installation creates a reverse lap at the top of the tape, creating an opportunity for water to get behind the tape at the upper edge of any horizontal tape.
While this reverse lap might not result in leakage in laboratory conditions, in the field the installation of the tape is not always done properly. At times the wrap is not clean when the tape is applied. Other times the surface is damp, preventing the tape from adhering properly.
Many of the problems related to the seam seal tape start with the wrap installation, particularly the fastener placement. Oftentimes cap fasteners installed at the tape edge prevent a complete seal. Wrinkles in the wrap can leave voids at the tape contact surface.
All of these conditions can allow water to migrate behind the tape, follow the horizontal seam to the nearest vertical seam, and ultimately into the structure. Since most areas of housewrap are over wood-based sheathing, leaks at the seams may go undiscovered for years.
Water entry leads to litigation
There have been litigation cases where the major contributing factor was improper sealing of the housewrap causing major structural damage to the wood sheathing and other building components.
Except under rare circumstances where the reverse lap is part of a small repair, our company would never recommend a reverse lap installation. Manufacturer’s window installation details no longer recommend wrapping housewrap into the rough opening and then taping the window head nailing flange to the wrap as an effective means of sealing the window. They now indicate a weatherboard installation.
Why not use double-sided tape?
We have contacted one of the larger housewrap manufacturers about these problems and asked about the possibility of a double-sided tape for use on horizontal seams. We were informed that they make such a tape, but it is not for sale in the U.S.
We will be contacting all of the manufacturers to attempt to encourage them to provide a double-sided tape or other method to eliminate reverse laps.
Until such tape is available, when you are sealing the horizontal seams make sure to follow all of the manufacturer’s instructions and recommendations, including making sure the wrap is clean and dry and that you are installing the tape within the effective temperature range of the tape as stated by the product manufacturer.
Additionally, make certain that fasteners and other objects are not installed in a location that will prevent or compromise the complete seal of the tape. Always use a roller to bond the tape and never rely on smoothing it out with your hand. Care must be taken and attention to detail is critical when installing the seam tape at transitions to avoid gaps between the tape and the wrap.
For any additional information or details always consult your housewrap system manufacturer’s details and specifications.
This article is © Quality Built and is reprinted with permission.
Jeff Hoch is an architect and field consultant at Quality Built in San Diego, California. Jeff has been involved in the inspection industry and related fields for over 23 years.