Repairing T1-11

[ironhat]

The T1-11 on the back of my garage has pockets of rot not more than two feet up from the bottom. I have corrected the cause of the rot and was about to replace the entire wall when a neighbor offered up a suggestion. Since the remainder of the wall is solid with no signs of delamination or rot he suffested that I gut off the bad section along the entire length. Then, have a piece of aluminum bent into a 'Z' and insert it up under the old material and then, the new material up under the other leg of the 'Z'. Since the back side of the garage faces woodland there wouldn't be an aesthetics issue. I'm wonder if I wouldn't get water migration along the horizontal plane of the aluminum. Yes, silicone caulk is in order but I don't trust it. I've considered allowing that horizontal area to drop downward, and then caulk that junction and the resulting cap on each extreme end of the garage. So, is this just too cheap for words or is it a viable solution with the proper cautions considered?

[LarryG]

What you propose is exactly the way many plywood siding installations are done when the wall height exceeds the panel length. You should be able to find a pre-made piece of flashing that is just what you need.

Flashing and waterproofing are all about the workmanship. Shape the flashing to shed the water, provide a drip edge at the bottom that's well clear of the panel face, and then seal the cracks so water can't get in via either the wind or capillary action ... if you've done all that, that's about all you can do.

(If you're not already planning to do so, you should also add a row of horizontal blocking within the wall at the seam.)

[dbhost]

You are talking about using Z strip, and yeah, you could do that. I have extensive damage to my T1-11, and I figure this is as good of a time as any to increase my insulation, and add Hardi Panel in lieu of the Masonite crud that is on my house...

It depends on what you want to do, and your budget. I live in a Wind storm prone area, and Hardi Panel has a LOT of advantages over traditional siding, including soem SERIOUS insurance discounts...

[JSUPreston]

Please, I beg of you to make sure you are wearing high quality gloves when working with z channel.

Either my sophomore or junior year of high school, I was helping a mission group build a lodge for a children's home. I was putting the z channel up on a 2nd floor outdoor balcony when it slipped. In an effort to protect my head, I tried to catch it. I nearly lost my right thumb at the 1st knuckle. Fortunately for me, it cut at an angle. Had it gone straight it would have sliced right through the joint. Took several stitches to get me back together, and YEARS before I got all the feeling back.

[crokett]

Ironhat, I fixed the siding on a shed at my old house using the method you describe. I made sure the flashing was bent so it shed water from the horizontal surface and there was a drip edge on the lower piece.

[ironhat]

Thanks all for some good points that I hadn't thought of. By drip edge do you mean to angle the bottom (exposed) edge away from the siding? Do you think that I should double the thickness there? I'm also thinking that if angling away is what is meant it might be a goo idea to run a bead behind it as a bit of support.

[crokett]

The whole piece should look something like this:

|
\__
| < drip edge

where the drip edge is a fold in the middle of the bottom piece and is spaced 1/2" or so off the face of the new T1-11. This way the water can't work its way back under the flashing through capillary action. Windowsills outside have a dado cut in the underside to act as drip edges.

[pelligrini]

You want to make sure that there is a gap between the bottom of your old sheathing and the z-flashing too. That joint should not be caulked either.

There is a pretty good detail here http://www.pathnet.org/si.asp?id=506

[ironhat]

Ahhhh, like a roofing drip-edge. Sorry I was so thick and thanks for the graphic for the dim of wit - me!

[pelligrini]

It's a pretty commonly found item. I know the lowes around me carries one smaller size.

If there is a building paper membrane behind the exterior sheathing you would want to overlap the top leg of the flashing. Any water infiltration behind the sheathing should run down between the paper and the exterior sheathing and exit at the flashing. That's another reason not to caulk that joint.

See Figure 5 on page 4 for an illustration http://buildingcodes.jocogov.org/doc...in%20walls.pdf

[LarryG]

pelligrini is correct ... you don't want to fill every void with caulk just because a void is there. You have to provide a means for water to drip clear without being wicked back into the siding.

I don't think anyone has mentioned that cutting the bottom edge of the existing siding on an angle, to match the slope of the Z flashing, is preferable to leaving it square. But if you do this, you still need to leave a gap between the sloped bottom edge of the plywood and the sloped leg of the Z-member that is wide enough for water to drip off and not be drawn back uphill.

Re: the bottom edge of the drip, our details always call for hemming this edge because it helps hold the edge straight and looks nicer. But we're typically dealing with wider pieces (coping, counterflashing, etc) than your Z-section will be, and they're custom fabricated by a sheet metal shop or roofer. The stock roof drip edges I've seen around here are not hemmed and I'm guessing the stock Z-section won't be, either.