I’m about ready to put all my windows in my new dormer and needed some advice on flashing the window openings. I haven’t yet housewrapped the house. Do I have too before I put the windows in? I’ve seen lots of builders flash the openings with tar paper then put the windows in and house wrap later. This is what I would like to do. Any problems with this method? Or any better alternatives?
Craig
Replies
Use Vycor. Its a self adhesive rubber flashing.
flash the RO sill, wrapping the Vycor over the paper on the outside.
Run strips of Vycor up along the sides of the RO on the sheathing.
Install a final strip of Vycor over the head flashing.
You need to leave the bottom of the sill flashing loose so you can get the housewrap under it. The wrap goes over the rest of the flashing. Think thru the path that a drop of water would take, you want to shed it to the outside, not funnel it in.
-- J.S.
Here's the Tyvek method... highly recommended (this same method is increasingly shown on window manufacturers sites and is also on the Typar site). You need to splurge on a roll of Flexwrap to make sill pans, or actually buy/make a galv or copper sill pan. IMO any window install without a sill pan is asking for trouble. I figure the cost of Flexwrap and Vycor for an average window install at about $20.
http://www2.dupont.com/Tyvek_Construction/en_US/assets/downloads/K02107HRBeforeInstall.pdf#search=%22Tyvek%20window%20flashing%20details%22
The same detail can be done with felt as well, which is what I like to use rather than wrap.
On the west coast our houses are already covered with a shell of shear ply before the windows are installed. Heres how we do it most of the time. I uses 6" strips cut out of a roll of bituthane instead of vycor. It is better and cheaper. Tar paper up to the window sill Flash the sill over the plywood and fold an inch or two inside the sill surface. Now install the window. No need to caulk under the fin if you use bituthane but you can if you want. Apply the side pieces over the fin and then install the tar paper and siding. Before the siding goes over the top and after the tarpaper is applied, flash over the head. The tar paper should be cut so that it just overlaps the fin but does not fit tight to the window. This gives the bituthane something to stick to when you flash the head. I always use 30# tarpaper because I think housewrap is bogus.