Hot Topics: Fixing a Rotting Shed

DoItYourself.com brings novices and experts together in our Forums, where they share questions, ideas and advice. Over 250,000 members post in more than 120 categories, so each week we highlight a conversation that may help you with your next DIY project. This transcript has been lightly edited for clarity.

Original Post: Dealing with wood rot at bottom of T111

EdShnatter Member

I have a 20 year old shed. Putting a new roof on it and going to paint it—the roof was leaking for too long and some T111 near the top rotted.

On the shaded / north sides of the shed, there's a very light green tinge—algae?

I'm spraying with wet and forget and just looking at things close.

I noticed that some of the lower parts of the T111 are rotting away. As you can see in the picture it doesn't have standing water / not near the ground. Is that just what happens after 20 years of being outside getting rained on?

To repair that / keep critters from getting in, do you just make a cut at 1 or 2 feet high all the way across and replace that lower part for the whole length of the shed? Or try to pin down the bad areas and cut to the next studs on either side / just replace that 1' high by several foot wide piece?

Yeah, and I'lll paint the bottom edge. Not sure if that was painted or not. Keeps moisture from getting in.

Is there pressure treated T111? Should I use that?

I keep saying it is a 20 year old shed.... how long should it last? But I am spending $$$ on a new roof so I hope it lasts a while.

rotting baseboards on a shed

the bottom of a rotting shed

Norm201 Member

What you're proposing will work fine. 20 years on a T111 shed is good. Especially if no special care is taken. I'm on my second 20 year shed that I built. Unless you use special guards or wrapping I don't think you'll get much more than 20 years. I also don't think putting too much effort is worth it on a shed to go more than 20 to 25 years.

Pilot Dane Group Moderator

I would make a saw cut up 12" or whatever. Then sheet the bottom of the shed with roofing tin or galvanized steel flashing. Tuck the metal up underneath the T1-11 so water will shed off the T1-11 and onto the metal.

joecaption Member

Why is it rotting and molding up?

Likely there's not enough roof over hang, no gutters, lack of proper sealing, and the shed was set to close to grade.

I'd be snapping a line at 4" and cutting out and removing the bottom T111, sealing the cut then prying out the siding, installing pieces of Z molding and replacing the old wood with 1X6 PVC lumber.

EdShnatter Thread Starter

I'm replacing the roof. Now I notice the (small amount of rot) on the bottom. but other than those, it seems in good condition. I've been debating replacing the shed—it's 10x16 with the cost of the new shed and disposal of the old (someone mentioned selling it on Craigslist!? Wouldn't have thought of that). vs. keep this one going.

I posted in the automotive section - I have a 2010 Honda Civic with 150K miles. Runs great, except that the A/C compressor died (actually, maybe just the clutch coil failed). What do you use as a rule of thumb for keep something going (shed, etc.) vs. toss it.

Pilot and Joe—that Z moulding is to keep the new wood drier, right?

Something I'm realizing—this shed was built with staples throughout. What would you use to attach the new T111 to the studs? Galvanized / deck screws? The studs likely don't line up with the cut channels. Just have to screw where needed? The staples are nice because they aren't too noticeable. Or should I get a staple gun? Or nails?

EdShnatter Thread Starter

What do you think of this? adding the blocking? Maybe not every stud? and nail / screw into these also? Or the 16" stud spacing is enough to give the boards rigidity?

a man drills wood repairing a shed

marksr Forum Topic Moderator

I'd use screws or nails, screws hold better but nails generally look nicer. The Z flashing keeps water from collecting where the new wood and old siding meet.

aka pedro Member

How is the framing? Assuming the structure itself is solid, and has a treated bottom plate, there is no sense to replace it. Since you are at that point of considering that option though, and, again, assuming the framing is good, I would suggest looking the rest of the siding over good to make sure it is solid, and if not you could remove the T111 completely and install new. If you do find that the siding is solid, and wish to repair just that bottom, I would go the route that Joe suggested with PVC lumber along bottom and a Z channel on top of that.

It’s honestly not that bad a job to tuck the Z channel up behind the old siding once you get it cut straight. For nailing new siding, I like to use 7 penny nails that they make just for this purpose, because they hold as adequately as an 8 penny, but have a little smaller head. If you do cut off just the bottom strip of the siding, the blocking you asked about would be a good idea because the siding will otherwise eventually bow where it does not have a flat surface behind it. But, being a shed, I do not know that I would consider it essential.

EdShnatter Thread Starter

Thanks! Aka - overall, the shed is sound. That was the debate I had in my head about replace the roof or get a new shed. I'm seeing this rot in some areas near the bottom of the siding But once I take off that 1' at the bottom... we'll see what I found. Treated bottom plate? I know they said it was on treated 4x4s. The bottom plate is what the flooring sits on? Or the bottom 2x4 that the vertical studs sit on?

7d vs. 8d. There's more to a nail description than that, right? would you use galvanized? Common, not finishing, right?

Oh, I missed that! Pilot is saying replace the bottom part of what was T111 with metal?! And Joe was saying just a piece of 1x6 plastic! What are your thoughts on the aesthetics for either of those vs new T111? Yeah it is a shed.

I am going to add this to my other roofing question also, but what are your thoughts of using pressure treated 2x4s whenever I'm replacing 2x4s or for this new blocking? From what little I know, it's wet when you get it / can warp over time more than an untreated 2x4?

marksr Forum Topic Moderator

Unless you expect the wood to get wet or touch the ground I wouldn't bother with pressure treated. You always want to use galvanized nails on the exterior or when nailing into PT wood. IMO a treated or PVC band along the bottom replacing the rotten siding will look fine.

aka pedro Member

Okay, so skip what I said about treated bottom plates. They're SOP for me when building on a slab, so just rolled out as I was typing, but sounds like yours are not on a slab, and they're in good shape, so ignore that part. And no, I would not use treated any place else; it's heavier, it's more costly, it can be harder to cut, it can twist significantly, and it's not necessary. You should find the 7-penny's I mentioned right in with the other nails; yes they are commons and yes they are galvanized.

sdodder Member

I recently had exactly the same problem. Repaired it the same way Joe described. It worked out great. I didn't use any blocking at the seam and haven't noticed any warping. Good luck!