Flashing to T1-11 sheathing?

[MushCreek]

I built my barn as cheap as possible, so it is sided with T1-11 siding. It is just one layer; no sheathing under it. Now, after the fact, I want to add some exterior features, including another man door, windows, and a small roof over the overhead doors. I'm trying to figure out how to flash these features in a way that will keep water out.

I've done some searching on-line, and there are several possibilities. One is to simply surface mount the windows and caulk the living hell out of them, and monitor and maintain said caulking regularly. The better way seems to be to remove the T1-11 from the area, and attach the window or door to the framing, then apply the T1-11 over it. Flashing an attached roof will be trickier. I thought maybe cut a slot with a circular saw set on a 45 degree angle across the wall, then another cut below it to remove a strip of the material. Shove flashing up behind the T1-11, bend it out to accommodate the roofing, then put the strip of material back to close the gap. I could use a similar system above the door and windows.

My two concerns with that method would be 1), keeping moisture from rotting the T1-11 where it meets the flashing, and 2), How to terminate the end of the flashing so it doesn't leak there.

If I had the time and money, I'd use the T1-11 as sheathing, install everything, then put some kind of siding over it, but that involves 1000's of dollars I don't have. Thoughts?

 

[oldcarpenter]

Really no good/easy way to do it.
I would flash right over the siding and use a GOOD caulk, with maintenance. Urethane caulk preferred. Also hem the top edge of the flashing to create a thicker spot for caulk and prevent the sharp edge. Cutting and flashing behind the siding will allow the rot to start on the vulnerable plies exposed.


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[Bretny]

My 12yr old garage was built with T1-11. The windows are cawlked into place and surface mount. My gabel end has the second corse (above 8') flashed to each other with Z flashing...both are equaly as rotted. T1-11 *****.

I did make 12in overhangs when i redid my roof..next is new construction windows and vinyl siding.

 

[DFB]

Ya I've done a couple of large sheds using T-11 but all were properly flashed between horizontal joints during the original build

For the retro windows install, seal over the mounting flanges with ice and water shield first then trim. And you can neatly caulk behind the trim for added protection. I did our donut shop shed that way added 3 windows after the fact been years nothing leaks


Shed roof overhang surface flashing and caulk won't look great but its been done. Best way would be to remove a piece of the siding first. how much wall is above the new roof?

Thinking now maybe could flash roof to wall then a piece of ice and water shield to seal and install a trim board caulked also. IMO look neater anyhow

 

[lakeroadster]

My two concerns with that method would be 1), keeping moisture from rotting the T1-11 where it meets the flashing, and 2), How to terminate the end of the flashing so it doesn't leak there.

Thoughts?

T1-11 gets a bad name, because 9 out of 10 installations aren't done correctly and or it is not maintained correctly. Our home was built with it in 1978. It's still great.

I go around and touch up the paint on a yearly basis, focusing on seams and the ends of the sheathing.

The key is to follow the instructions.... and everything you need to know... is right here..
https://lpcorp.com/resources/produc...groove-panel-application-instructions-english

 

[SGKent]

paint both sides and all the cuts, and T1-11 will last a lot longer. Caulk where needed but do so in a way that won't trap water or allow capillary action. Keep it painted.

 

[PugetDude]

If you're going to surface mount the windows, I'd recommend paiting both sides of your trim first, then...

1. Mount the window with low-profile truss head screws.
2. Trim out the sides and bottom of the window with **** cuts, the sides extend below the window. That way any water that makes it past your flashing will have an escape path.
3. Install z-flashing above the window, extend it a bit beyond the side trim and crimp the overhanging edge down to create a drip edge beyond the trim.
4. Liberally caulk the top of the z-flashing with Big Stretch caulking. Fill the grooves and feather the caulk up with a popsicle stick or screwdriver to divert the water onto the flashing, not behind it.
5. Install the top trim board. Caulk it at the top and sides only, again making sure the water is diverted out of the grooves and onto the top of the trim.

 

[DFB]

Can't say if T-11 was better 30 years ago but that's how long ago my first out building was built been thru some long winters too, snow often drifted high up against the walls. Oil stained it only twice over all that time (though really needs it once again )

Siding has held up extremely well no punky wood or rot.

Even my trim pine/fir trim boards are all good

 

[Bretny]

Can't say if T-11 was better 30 years ago but that's how long ago my first out building was built been thru some long winters too, snow often drifted high up against the walls. Oil stained it only twice over all that time (though really needs it once again )

Siding has held up extremely well no punky wood or rot.

Even my trim pine/fir trim boards are all good

Oil based stain is prob why it lasted so long. Oil based soaks in all the cracks and seams. Paint hardly does this.