How to address gap under window sill
I was pulling trim and notice that there is a gap between the window sill flashing and the vinyl siding channel. See photos.
My plan is to
1) stuff 3/8″ or 1/2″ backrod as far as I can go
2) fill with spray foam (non-expanding)
Should I also caulk the seam on the exterior?
We’re about 5 years away from stripping to sheathing and re-siding the house with a new WRB.
For context, the external wall assembly is
– vinyl siding
– 1/2″ foil faced foam (EPS?)
– cedar shingles
– tar paper(?)
– board sheathing
– mix of fiberglass and blown in cellulose (new cellulose from MassSave)
– lath & plaster
– gypsum drywall
I’m going to try to get the backer rod all the way to the vinyl siding.
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Replies
Windows need to serve many functions, including being part of the air control layer, the thermal control layer and the water control layer. There are several different installation techniques that provide all of the above. Your current situation has none of the above.
The most important layer is the water control layer. The best way to handle that is with a sill pan that can drain to the exterior. Another approach is called the full barrier system, commonly done on job sites but generally frowned upon in the building science community. For a full barrier system you can seal it as you describe.