I’ve been wanting to write this column for years. The topic has been a burr under my saddle, but I needed to base the column on proof, not speculation.
That proof arrived last week in a desperate phone call from my son-in-law. He and my daughter are having a new home built in Maine, and rainwater was leaking into their home across the tops of windows, just days before the drywall was to be installed. I predicted this might happen — and, sure enough, it did. (I’m not the builder of this home, but I am their principal adviser.)
I’ve been aghast at a growing trend in the residential construction industry over the past few decades to abandon hard-earned, tried-and-true construction methods that were developed and used by builders for centuries. Specifically, I’m talking about the explosion of flashing tape that’s being installed around countless windows and doors in homes and room additions.
Each day, older craftsmen and craftswomen die, and often they take their knowledge with them to the grave. Young homebuilders are left to try to come up with solutions to problems on their own — if they’ve failed to pay attention to these older builders.
The water that was leaking into my daughter and son-in-law’s new home was happening because the construction detail that’s intended to prevent a leak depends on the adhesive on a piece of tape. Should the adhesive fail, water is sure to enter the house. It also depended upon methods of the person installing said tape. Another disturbing trend I’ve been observing is the disappearance of skilled laborers, but that’s a column for another day.
Mother Nature knows all about how to shed water to keep things dry. Apply your critical-thinking skills to how feathers are layered on birds. Think about how the fur is coated on animals that need to survive outdoors in cold and rainy climates.
This same simple technology was used for centuries by builders to create dry and rot-free wood structures. Roof shingles and flashings are layered on roofs like feathers. Each shingle on a sloped roof overlaps the one below it, and gravity pulls water over the roof and down to the ground.
Builders of old used the same method to keep walls dry. They overlapped pieces of asphalt-saturated paper in the same overlapping manner. When the paper came to a door or window, the builder carefully installed a simple metal flashing that extended up the wood wall, was bent to pass over the top of the window or door trim, and was bent a final time so about 1/4-inch of the metal lapped over the front of the window or door trim.
The metal was angled out slightly from the window or door trim to prevent capillary attraction from pulling the water up under the metal flashing.
Water dripping down behind the siding, brick, stone or stucco would flow across the asphalt-saturated paper that overlapped the metal flashing on the wall. The water would then roll across the metal flashing and then flow out over the front of the window or door.
That simple, yet remarkably effective building detail is being sacrificed at the altar of “build it faster.” Most modern windows and doors have a built-in weatherproof nailing flange that can take the place of the older metal flashing. The top nailing flange just needs to be placed behind the overlapping layers of weatherproof barrier above it. This weatherproof barrier is required to protect the wood framing of the house from water that gets behind siding, brick, stone or stucco.
Many — but not all — builders and laborers are using wide flashing tape that overlaps, rather than underlaps, the materials above it. They hope that the adhesive doesn’t fail, because if it does, water will get behind the tape and it’s game over.
I’ve maintained for years that it’s possible the adhesive on these tapes won’t stand the test of time. Can the adhesive survive thousands of expansion and contraction cycles when the sun beats on a wall and transfers that heat to the tape?
My biggest beef is with the tape that’s applied to the popular plastic-coated wall and roof sheathing. Any hopes for a dry structure are based entirely on whether or not the tape adhesive was installed perfectly and holds forever to that plastic coating.
As a builder, I’m not a big fan of hope. You should only hope for things you can’t control. You can control how to make sure your new home or room addition never leaks. Just follow in the footsteps of the master builders of old.
Tim Carter has worked as a home improvement professional for more than 30 years. To submit a question or to learn more, visit AsktheBuilder.com.