Why Wall Flashing Installation Errors Are So Common
Originally published by: The Journal of Light Construction — August 27, 2020
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As Christine Williamson (the architect behind Instagram's Buildingsciencefightclub) explains in a recent IG post, lots of builders confuse the cladding of a building with the building's water control layer, and, she surmises, this is the reason for a very common omission: Not installing through-wall flashing, the (usually) L-shaped piece of metal above an opening or at the base of a wall.
In her post (embedded below), Ms. Williamson aptly notes that installing through-wall flashing and allowing water to drain out is a much more reliable approach to protecting a wall from water damage than trying to prevent water from entering in the first place. As she says it: "You will never be perfect at keeping 100% of water out of the wall - in providing drainage, you don’t have to be. This isn’t a compromise position that 'accepts' poor craftsmanship, it’s just smart design."
Be sure to click on all the slides in the post above to understand the scope of the problems and Ms. Williamson's guidance on solving them.
It's surprising to us here at JLC that this omission continues to be so prevalent after all the attention we have brought to it over the years, but we agree with Ms. Williamson that it remains incredibly common.
One solution that works on cantilevered areas is to build a drainable reveal. Click to enlarge.
Stucco buckets. One distinct and especially thorny problem Ms. Williamson points out is a problem we earlier dubbed "stucco buckets" - overhangs where stucco wraps from the vertical wall to the horizontal surface without anywhere for liquid water to drain out (see "Avoiding Stucco Buckets"; Nov/18).
One solution is a drainable reveal, with variations that work for stucco (shown left), as well as thin brick. Another option described in "Avoiding Stucco Buckets" is to divert the water with a channel that drains the water away from the bucket (the closed cladding above an opening).
As Ms. Williamson notes, the omission of through-wall flashing is especially common with stucco, but it's not the only cladding that gets short-changed. Providing an escape route for water is vitally important for all cladding.
Here are some good resources for detailing through-wall flashing in a variety of cladding types:
- Masonry Through-Wall Flashing at Windows
- Installing Effective Rainscreens
- Best Practices: Adhered Concrete Masonry Veneer
- Synthetic Stucco Without Failures