What's the best way to install a new construction window in T-111 siding? If
you just place the window against the siding you have all the grooves leading
underneath the window flange on the top and bottom. I don't like the idea of
just a caulk to seal things well, although maybe that is the practice.
I was thinking of trimming the rough opening with a 1 x 4. The T-111 would butt
against this and the window would seal against the face of the 1 x 4. It still
leaves you with lots of butt joints to caulk around the 1 x 4, but at least no
grooves leading underneath anything.
We used a rough sawn plywood on our house, basically T-111 without the
grooves. I applied caulking under the window flange, then again around the
outside of the flange. We then used 5/4 cedar to trim out the window, and
that too got caulked. So, there are basically three layers of caulk as
protection. Not the ideal situation, but there aren't any good solutions
when you can't overlap the flange of the window.
One option I heard a few years ago was to use a circular saw and a straight
edge to cut an angled slot above the window (45 degree's, sloping down so
water can run out). Install the Window, then tuck flashing up into the
groove, overlapping the flange of the window. You could probably cover that
with trim and caulk to make it look better.
Of course, that only works with a square window. That approach wouldn't
work very well with our arch top window.
If the siding isn't up yet, put the window on first. If it is, I would
paint the T1-11 first, then install the window, put on rubberized window
flashing (the peel and stick kind) on each side and the top (in that order)
and finally install Miratec for trim. Leave 1/8" gaps between the trim
pieces and between the trim and window. Caulk with silicone if you are not
going to paint and polyurethane if you are.
That's a nice situation for the top of the window, but the side and bottom
window flanges would end up under the siding. Wouldn't any water running
down along the edges and bottom of the window end up behind the siding?
It's also easier to install windows after the wall is built, and makes
window replacement easier in the future.
Water running down the face of the window should drip off the end of the
sill. There shouldn't be much water coming in from the side although the
sides should be caulked and covered with flashing membrane in the same
manner as the top.
Replacing the window some decades down the road would be a little easier if
the window was on the outside of the T1-11. Saves the work of slicing the
plastic nailing flange off first.
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