Window Head Flashing w/T1-11 Siding

[neubanksc5]

I'm looking for a detail of a finned new construction window with t1-11 siding and 2x trim all the way around. I can't visualize in my head how the t1-11 would be cut to install the flashing. Only way I can think of is installing the siding, holding a piece of trim to the siding to see where the edge is and then kerfing the siding to install the flashing. Seems like there would be a better and easier way to do it, which is why I'm asking ya'll for help. Thanks!

[NW Architect]

Re: Window Head Flashing w/T1-11 Siding

Start by figuring out two things:
1. Detail between trim and siding: You can overlay trim ON the siding, butt the trim to the siding with a rabetted edge on the trim, or butt trim to siding with a sealant joint. Your options may be limited by the amount of framing you have at windows and the presence or absence of nailable sheathing
2. Will you be using a sheet metal head flashing? If so at top of window, at top of head trim, or both

[dgbldr]

Re: Window Head Flashing w/T1-11 Siding

You didn't say if this is new construction or retrofitting a window into existing siding.

Around here T1-11 was done as sheathing AND siding, i.e. no sheathing under the T1-11. I haven't seen any flashing detail that can properly compensate for that.

If existing, I would treat it as if the T1-11 is the sheathing and then pretend that the trim is the siding. Maybe some sealant and bevel the head trim for drainage. And pray.

If it's new construction, I just wouldn't do T1-11 without sheathing.

[Norm Yeager]

Re: Window Head Flashing w/T1-11 Siding

I would cut the T111 about 1/2" above the top of the trim and slide the flashing behind the siding and lipped over the top of the trim with the ends of the flashing folded down over both ends of the trim. Keep the siding up off the flashing about 3/8" to let the water drip off the siding onto the flashing with no wicking. I'd run the head trim long over the side trim and bevel it where the side pieces butted into it. The side pieces run long with the bottom piece butted into them. This still leaves you dependent on sealant around the two sides and the bottom of window between trim and window. I'd also bevel the bottom portion of the trim that sticks beyond the window sill. Run a saw kerf in the bottom edges of the side trim and the bottom piece so water drips off rather than running down siding. I'm interested to see more responses. I think this is one of the tougher flashing problems to get it right

[neubanksc5]

Re: Window Head Flashing w/T1-11 Siding

To clarify a couple things:

1. This is all existing construction. We do a lot of HOA / Property Management type work, which includes lots of trim replacement.

2. All of the homes we've worked so far like this will have T1-11 Siding with the 2x6 (typically) trim installed on top of the T1-11. Most communities we work in have shearwall behind the siding, but a few communities do not.

3. Flashing to preferably be sheet metal on top of head trim

[S.Joisey]

Re: Window Head Flashing w/T1-11 Siding

This was discussed at he end of this thread:

http://forums.jlconline.com/forums/s...ighlight=T1-11

[David Meiland]

Re: Window Head Flashing w/T1-11 Siding

There is a pretty good way to do this, although it takes some careful cutting of the T1-11, and it takes a particular order of work. It does not depend on having sheathing in place, although it's easier since you have something to push against as you install the SAF.

1. Install the wrap or felt.
2. Install the window.
3. Cut the head trim to exact size, and cut a piece of Z flashing for it.
4. Use the head trim as a spacer to position the Z flashing on the wall EXACTLY where it will go, and nail the flashing.
5. Tape the window and the flashing in and lap the wrap, etc.
6. Cut the siding panel with a hole for the window (hole = outside of frame + a hair) AND another hole for the flashing. The two holes are not connected. The hole for the flashing is ~3/4" tall and as wide as the flashing, and the bottom edge of the hole is set the tuck right under the flashing. It's like a mail slot.
6 and a half. Use a router to rabbet the back of the siding for the window flange, usually about 1/4" deep by 2" wide all the way around.
7. Install the siding.
8. Install the trim. Tuck the head trim under the head flashing.

The hole you cut for the flashing has to be perfect. You have to measure carefully from the adjacent piece, and it really helps to have a track saw. The cut in the siding that's above the flashing is very visible after the siding is up.

Of course some times the window is captured by two pieces of siding, so you have to project your cuts over both pieces.

Allow extra time for the first few openings. Then it will start getting quick and easy.

[NW Architect]

Re: Window Head Flashing w/T1-11 Siding

Easier way, if trim is set ON the T-111 (which it will have to be if the framing is existing - nothing to nail T-111 to outboard of the trim): Flash at the top of the window, not at the top of the head trim.

The plant-on head may run afoul of code requirements for "continuous flashing over projecting trim", depending on how projecting and trim are interpreted in your area. I mitigate by ripping the top to slope, priming all sides, and priming the mating surfaces of T-111 then get specific AHJ approval as an alternative means and methods.

If trim is to be painted, I will sometimes even coat the trim pieces all over with CPES, or upgrade the material to a less water sensiteive material

[David Meiland]

Re: Window Head Flashing w/T1-11 Siding

NW, in my description above, the T1-11 is nailed next to the window frame and the trim is planted on.

[NW Architect]

Re: Window Head Flashing w/T1-11 Siding

Ah. THAT's why the two cuts are not connected to each other!