Forgive my ignorance, (very new to DIY/home improvement), but I was wondering if anyone has seen this before.

I'm converting a detached 3-car garage that was made in the 50's to a studio apartment. When I ripped into the drywall (since there is no insulation) I saw the siding nailed into slats instead of plywood. The problem I see is that it leaves openings near doors/windows that allows water in.

Is this something I can work with or am I going to need to remove all of the siding, remove the slats, install plywood, and re-install the siding?

I'm at work but will try to post pictures later if anyone is curious.

The siding and trim around the windows should keep the water out. It's not the responsibility of the sub surface.

Do you have evidence of water intrusion?

Some of the studs around the door appear rotted (could just be cause they're old), but without the drywall you can see outside through the spaces between the slats. If insulation were present it would easily get wet during a rain at least near the door. Looks like the vapor barrier is frayed in some places as well.

What kind of exterior siding? If you're seeing daylight then your exterior siding is your first problem.

Don't see any issue with patching any rotted sub surfaces if you replace the exterior siding.

It's shake (cedar I think). Definitely old & weathered in spots needing replacement. I've only seen the light by one door, still in the process of removing drywall & I plan on relocating that door anyway. If I can lay more vapor barrier & replace the shake where it's weathered without installing plywood that would save me a ton of time & money.

Today we use plywood or osb as sheathing. Neither of these are rated to be wet which is why we cover these with house wrap and siding. The siding is the first level of protection with house wrap behind it. You do not need to replace the sheathing, but you do need to keep it dry. In the days when we didn't insulate walls, they dried easier. With modern building and insulation practices, you need to make sure things will stay dry.

Mr. Havok said:

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It's shake (cedar I think). Definitely old & weathered in spots needing replacement. I've only seen the light by one door, still in the process of removing drywall & I plan on relocating that door anyway. If I can lay more vapor barrier & replace the shake where it's weathered without installing plywood that would save me a ton of time & money.

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When you said slats for siding I immediately thought it must be shake. A lot of old garages were done that way because wood was cheaper than plywood (or maybe the carpenter was an old guy. and that's the way he did it was he was a boy) and they didn't see a reason to spend a lot on sealing up a garage. I'm betting most of your issues with the shakes are below the 3' line. Maybe you could remove the bottom 3' or so, install a vapor barrier and then create a wainscot.

That's something I had not considered. I'll do a bit of research on it.

Talking with my uncle who has DIY experience he seems to think we should remove the shake/slats and get plywood up. I think it sounds like a pain in the ass, but I don't want to half ass this either while I have this structure to its bare bones.

Mr. Havok said:

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That's something I had not considered. I'll do a bit of research on it.

Talking with my uncle who has DIY experience he seems to think we should remove the shake/slats and get plywood up. I think it sounds like a pain in the ass, but I don't want to half ass this either while I have this structure to its bare bones.

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The important thing is to have a consistent vapor barrier. Actually, in this case, vapor barrier isn't even the right word. You need a rain screen to keep water from getting into the wall cavity. If it has big holes or just doesn't exist, then you probably need to redo the whole thing.

Converting a garage to an apt is a heck of a project for a new DIYer.

Aggietaco said:

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Converting a garage to an apt is a heck of a project for a new DIYer.

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I've been quickly realizing just how large this project is. Fortunately, I'm a teacher so I'll have the summer to really devote my time to it.