The first time I used a self-adhered water resistive barrier was in 2019, on my own home. I had recently purchased a 1950’s vintage Cape Cod design fixer upper that was built using board sheathing covered by 15 lb. asphalt impregnated felt. I knew I wanted to improve the water management and air tightness of the structure but didn’t want to upgrade the sheathing. I had been researching self-adhered WRB’s and decided that option would be the best fit based on what I was trying to accomplish.

I’ve heard a few building scientists say as much as 10% of the water that contacts the cladding of a home during a severe, wind driven rainstorm may end up behind the cladding. Of course, the primary function of the WRB is to keep that moisture from moving to the water sensitive building components behind the barrier.
We’ve also figured out that it’s best if any moisture that ends up inside the wall, either from a construction defect that allows some water to bypass the WRB, or from air leaks that lead to water vapor condensing on a cold surface inside the wall, has a way to dry in at least one direction. This drying process is slow, by way of vapor diffusion. When outward drying is desired, the wall needs to have some level of permeability but remain both water and airtight. Many self-adhered WRB’s fit that bill perfectly.
Before we get into installing a window when using a SA WRB, we should first go over working with a self-adhered membrane. Basically, these products are large pieces of tape, with a slightly lower adhesive bond than you would find in quality construction tape. The product I chose to use at my home was Henry Blueskin. Blueskin comes in widths up to 4-foot by 100-foot-long rolls. The product can be used either horizontally or vertically with the only difference being the overlap of the seams. Horizontal applications require a 2-inch, shingle style overlap. A 3-inch overlap is needed when installing vertically.
Installation requires a clean and dry substrate, free of any oil or dust. Substrates can be OSB or Plywood (this includes board sheathing), exterior rated gypsum, concrete and some metals. If you are installing the WRB horizontally, it’s recommended that you snap level lines, so the product stays straight. It works best if you have at least two people for the installation, one unrolling the barrier across the wall, the second person peals the backing and sticking the WRB to the wall. My suggestion is to go slow, making sure to pull on the roll hard enough to remove wrinkles, but not so hard the membrane pulls off the wall. Don’t get too aggressive in sticking the WRB to the wall at the beginning of the installation, if there is a spot you are not happy with, often you can pull the product off the wall to reposition without damage (the nice part about not having an aggressive adhesive). If it’s rolled, that’s a much harder process. Once it’s in place, use a J-roller or squeegee to apply enough pressure for a full bond, making sure to work out any air bubbles that form.
Working with the product vertically is similar. Mark a plumb line on the sheathing and work the product from the top down, allowing gravity to help. In my opinion, a vertical installation is easier (this is how I applied the Blueskin to my home, solo). One additional piece of advice, the adhesive is very sticky if it touches itself. Applying solo on gusty days is not advised.
Preparing the rough opening
When installing self-adhered WRB’s, there are few different ways to address window and door openings. I’m going to cover Henry’s recommended installation first, and then a slight variation that I used on my personal house. I constructed a mockup for ease of photographing the process.
The first version is to install the Blueskin per the manufacturer’s instructions, covering any window (door or other planned opening). Once the WRB is installed, come back and mark the window with a two-inch cutback from the rough opening. Remove the WRB from the opening.
This two-inch cutback method for integrating a window into a WRB is gaining in popularity. Henry recommends this detail when using both their self-adhered and mechanically attached WRB products. The reason is to better prevent bulk water migration between the WRB and window rough opening by using a flashing tape with better adhesion bonded directly to the wall sheathing.
Once the rough opening is exposed, we prepare the opening for the window installation. First, install the sill flashing material. I’m a fan of sticking with one manufacturer’s products to maintain a system. (In the case of Henry, you’ll get a 15-year warranty when using their product lines.) The sill flashing tape used is Henry’s FortiFlex Butyl (very similar to Tyvek’s Flexwrap).
One trick I’ve found with installing flashing tapes, purchase a cheap wallpaper squeegee for working tapes into and around corners. Once the tape is in place, use a J-roller to get the pressure sensitive adhesive to fully bond to the subsurface.
Air sealing details
My next step is an air sealing detail. Where the window rough opening framing and exterior wall sheathing meet, and where the inside corner window framing connect, there is always a potential for air leakage. There are a couple ways to deal with this, the first is to install a sealant between the framing and sheathing and between inside corner framing members while the home is under construction. I choose to use a tape after framing is completed, this second detail would also be used for existing construction.
Installing the window
Once the rough opening is prepped, the window can be installed per the manufacturer’s instructions. Henry has its own line of sealants, two of which are used in window installations. The first is Moistop sealant, which is used to seal the window flanges to the sheathing. Again, follow the window manufacturer’s instructions, which will usually include the sealant being applied to the top and two sides, not the bottom. Once the sealant is in place, the window can be checked for level, plumb and square and then fastened into the opening.
Once the window is sealed and fastened into the opening, the metal (usually) head flashing can be installed. The head flashing detail was not shown in this mockup assembly, but here is a window head flashing we recently installed on a SA-WRB project that included a continuous exterior insulation. This detail required a more complex head flashing, we custom bent these on a metal break. You will be seeing more on this project, which we are calling Bojou Resort in the near future.
Next, we apply tape, first to the sides, from the window nailing flange, across the bare wall sheathing, and seal to the SA WRB. This alternative connection allows for the more aggressive tape adhesive to bond between the window and WRB, breaking the potential for moisture to migrate laterally which can potentially end up behind the WRB and window flange and enter the rough opening, a belt and suspenders strategy.
Because the head flashing tape is a reverse lap, Henry requires a bead of its Crystal Clear 212 Sealant be installed at the top leading edge of the tape, and troweled flat.
I’m not a fan of this detail, so I used an alternate installation method to address the window head flashing assembly on my personal home and other projects I’ve been involved in that use a self-adhered WRB.
My preference is to not install the Blueskin WRB over the window before the window install. This isn’t a big deal when working the eave end of a building, it can create a sequencing challenge on the gable ends. The process isn’t difficult, it just requires a little more planning.
The window is installed exactly like the first method, sealed in the opening using a sealant. Install the metal head flashing then tape the sides and the top. Once this process is complete then finish the WRB installation which is shingle flashed over the window, no additional sealant is required. Just remember that Blueskin requires a minimum of 3-inch overlap onto the adjacent, previously installed SA WRB.
Working with a self-adhered WRB isn’t as simple as the more common mechanically attached products. The membrane is more expensive, more challenging to work with, and a few different details will need to be learned. But there are a lot of benefits. A product that provides two control layers (water and air) into one application is a major benefit, and the primary reason I choose to use Blueskin on my personal home.
This post first appeared on the Green Building Advisor website.