Will this work for "fixing" my dry rot?

[williamkwong]

Hello everyone! I am getting my garage ready for the painters. I need to replace a lot of the T 1-11 siding because of about 3" of dry rot on the bottom. I want to just replace the bottom portion instead of replacing the whole sheet. This is mostly because I am doing the work myself and the cost.

I searched around the internet for some options and ran into this.

I will basically cut 10" off of the T 1-11. I will replace that 10" with CDX plywood of the same thickness. I will prime and paint all the sides, with careful attention to the exposed bottom edge. I will put a Z flashing between the 2 pieces. Then I will use a 12" tall piece of fiber cement to cover up the CDX and flashing. I will then run a bead of caulk above the fiber cement board to keep water from getting behind it. I will also fill those "holes" that are created with the grooves of the T 1-11 with caulk.

How does that sound? Do I need additional caulking? Can I nail up the CDX with the current vertical studs or do I need to place a horizontal stud where the 2 pieces of siding meet?

Thanks all!

Current

Proposed

 

[M17715]

Yes, you could do that. I am wondering why the wood has dry rotted at the bottom. Usually this happens because there are no gutters on the building. So, when the water runs off of the roof, it hits the ground and splashes back up onto the bottom of the siding- which causes it to rot. So, if this is the case, you might want to add gutters to avoid this in the future.

 

[williamkwong]

Yes. Lack of gutters and the siding is very close to the ground. Also new gutters went up before the last rain season. Thanks for the insight!

 

[timewarp]

That's not the best way to do it, you are trusting caulking to keep the water out, much better to just put the fibercement board under the z-strip so the flashing keeps the water out rather than the caulking. If you really want to have plywood behind the Fibercement board, just buy a z strip that's wide enough to cover the thickness of the fibercementboard and cdx.

Also when you place the Z-strip you don't want to jamb it up tight to the bottom of the T-111, leave about an 1/8" gap so if water gets on top of the Zstrip it won't wick up into the T-111 and cause it to rot just like the original did.

 

[astroracer]

That's not the best way to do it, you are trusting caulking to keep the water out, much better to just put the fibercement board under the z-strip so the flashing keeps the water out rather than the caulking. If you really want to have plywood behind the Fibercement board, just buy a z strip that's wide enough to cover the thickness of the fibercementboard and cdx.

Also when you place the Z-strip you don't want to jamb it up tight to the bottom of the T-111, leave about an 1/8" gap so if water gets on top of the Zstrip it won't wick up into the T-111 and cause it to rot just like the original did.

Ditto! This is what I would do:
1). Don't use regular grade plywood. Get some marine grade plywood that is designed to live in this type of environment. You won't need to paint it so you can put the price of paint toward the extra cost of the plywood.
2). Cut the strips 12" wide so you can use all of the plywood. 48" wide panels will get you 4 12" wide strips.
3). Make sure the **** seams land on a stud and use deck or marine grade panel adhesive to seal the ends as they are butted together.
4). Don't cover the new panel with anything. Water WILL get behind that cement board and it will cause problems down the road. Leave it open to drain and dryout.
5). Paint with good exterior latex paint to make it match the rest of the building.
Mark

 

[zcar751]

Ditto! This is what I would do:
1). Don't use regular grade plywood. Get some marine grade plywood that is designed to live in this type of environment. You won't need to paint it so you can put the price of paint toward the extra cost of the plywood.
2). Cut the strips 12" wide so you can use all of the plywood. 48" wide panels will get you 4 12" wide strips.
3). Make sure the **** seams land on a stud and use deck or marine grade panel adhesive to seal the ends as they are butted together.
4). Don't cover the new panel with anything. Water WILL get behind that cement board and it will cause problems down the road. Leave it open to drain and dryout.
5). Paint with good exterior latex paint to make it match the rest of the building.
Mark

Look to spend at least $75 a sheet. You will need to look for Okoumé plywood and will probably have to go to some place other than one of the box stores.
Replace it with more T1-11 and the z strip. Prime it and paint it and walk away.

 

[deter]

Replace it with more T1-11 and the z strip. Prime it and paint it and walk away.

this

 

[astroracer]

Ahhh, maybe I should have said what I meant... "Pressure Treated" Plywood. Still, 35 bucks a sheet at the "Depot". Better, I should have said pressure treated 1 x 10. That's what I did with my pole barn when the back fill started to rot the T-111.
Trim off the bad and add the PT 1 x 10 instead of plywood. Better?
Mark

 

[Tim The Tool Man]

As stated above, replace it with more T-11. 12 or 16" would be fine. Prime the cut ends top and bottom, use 'z' strip at your joint and also add a drip cap or 'z' strip at the bottom as well.

Also as stated above don't parge over the patch unless you plan to properly flash it. Also PT plywood would not be the best choice...

 

[skyking]

That's not the best way to do it, you are trusting caulking to keep the water out, much better to just put the fibercement board under the z-strip so the flashing keeps the water out rather than the caulking. If you really want to have plywood behind the Fibercement board, just buy a z strip that's wide enough to cover the thickness of the fibercementboard and cdx.

Also when you place the Z-strip you don't want to jamb it up tight to the bottom of the T-111, leave about an 1/8" gap so if water gets on top of the Zstrip it won't wick up into the T-111 and cause it to rot just like the original did.

This ^^^^^