The garage is rotten inside the drywall

[hedstrom]

I was going to start fixing the inside of the garage but discovered that it was completely rotten behind the drywall. The house is from 1930 but I'm not sure when the garage was built. As you can see in the pictures, all the old paneling on the outside was rotten, and the board at the bottom as well. There is now some metal on the outside of the paneling, and the rotten part is below ground level, but I suspect the whole side is like that. I was planning to excavate where the raised beds are next year to open it up downward as the plan was to put paneling on the outside of the asbestos cement, but I suspect it will become a bigger job. I originally only planned to fill and paint the old drywall in the garage to make it look a bit fresher.

How should I proceed now?
Should I cut the drywall along the entire bottom of the wall and remove everything that's wet?
Can I just replace the board at the bottom and put new drywall on the inside?
Any advice is welcome, as I wasn't planning to put too much effort into the garage this year.

 

[klaskarlsson]

From the outside, it looked surprisingly fresh, is it old (dry) rot or something ongoing? If it's ongoing, you should find the cause before replacing the wood.

 

[hedstrom]

From the outside, it looked surprisingly fresh, is it old (dry) rot or something ongoing?
If it's ongoing, you should also find the cause before you replace the wood.

It wasn't dry rot, it was wet and crumbled apart, tried to remove the worst parts and it looks like this now.
It's half a meter below ground in that corner, so probably water collecting and seeping in?

 

[klaskarlsson]

it wasn't dry rot, it was wet and crumbled apart, tried to remove the worst parts and this is what it looks like.
It's half a meter underground in that corner, so probably water gathering and seeping in?

Maybe it's a classic roof drainage problem (a downspout that's not directing water away from the facade?)
Easiest seems to replace it from the inside if the outside seems "ok"

Also, check the construction to ensure wood isn't directly against concrete, or of course, the ground.

 

[Eld]

Wood construction below ground will never be good. You need to install a new beam higher up and cast or build the lower part of the wall that is below ground.

A lot more work? Sure!

 

[hedstrom]

Maybe it's a classic roof drainage problem (a downpipe that doesn't divert water away from the facade?)
It seems easiest to replace it from the inside if the outside looks "ok."

Also, check the construction to ensure that wood is not directly against concrete, or the ground of course.

There are no downpipes on the garage now, but I'll put them up next year.

 

[hedstrom]

Wood construction below ground level will never be good. You have to put in a new sill higher up and pour or build with masonry the lower part of the wall that is below ground.

Much more work? Certainly!

The question is whether you dare to cut away all the rotten wood at the bottom and a bit up so that the garage doesn't sink, then screw a temporary plywood sheet against the wall and pour in concrete?

 

[klaskarlsson]

Wood construction underground will never be good. You need to put in a new sill higher up and cast or brick the lower part of the wall that is underground.

A lot more work? Certainly!

Ah right - didn't think about it saying "underground"

There are no downspouts on the garage now, but I'll add them next year.

The question is whether you dare to cut away all the rotten wood at the bottom and a bit up so the garage doesn't sink, then screw on a temporary plywood board against the wall and pour in concrete?

No gutters either then? You might want to try temporarily redirecting water from the corner where it seems to be coming in somehow?

I'm not quite sure how the construction is - normally there's a concrete slab, then something separating the slab and the wooden wall - not wood directly on it: And not wood underground.

Or it's a gravel floor, and then some form of posts/piers (in non-organic material) - but again, no wood against the ground anywhere.

 

[Eld]

The question is whether you dare cut away all the rotten wood at the bottom and a bit up so the garage doesn't sink, then screw on a temporary plywood sheet to the wall and pour in concrete?

You must somehow support all the studs before you cut them.

But I don't know how you would manage to cut the studs, put in a new sill, and pour in concrete (in a form that needs four sides and reinforcement) if you screw a plywood sheet over the whole thing.

 

[hedstrom]

You must somehow support all the studs before you cut them.

But I don't know how you would manage to cut the studs, put in a new sill, and pour in concrete (in a form that needs four sides and reinforcement) if you screw a plywood board over everything.

Yes, a four-sided form is impossible to achieve, and the back of the garage is next to the neighbor's property as well.

 

[Dublin]

An alternative to pouring/concreting is to lower the ground level on the outside where it is higher than the bottom slab.

 

[Eld]

Yes, a form with 4 sides is impossible to achieve, the back of the garage is adjacent to the neighbor's property as well.

Then you'll have to build a wall.

 

[hedstrom]

Now the inside is sorted with new studs and plasterboard on the outside, but when I removed one of the old studs inside, a fiber cement board on the outside cracked. How should I fix it? Right now it's open, so water can get in. Does anyone have a good tip? A new panel will be installed on the outside, but that will be at the earliest next summer.