My garage is leaking. I cut away drywall and noticed that some of the joists are rotting or damaged. There's mold, I think a lot. I think the cause of the leaking might be related to water that's pooling on the concrete deck above. I'm not sure what to do.

damaged joists water pooling on deck above garage mold more evidence of water damage?

1 Answer 1


...Fix the roof.

It's not complicated or mysterious - the roof leaks, so it's wet, and you need to stop that.

Which is going to be work if it's a concrete deck ( less if removable pavers so you can actually get to and replace the waterproofing under them. More if some optimist poured concrete over a waterproofing membrane that didn't last.) I see you have the latter case...

While it's easy enough to cut channels to remove puddles, that's not going to solve a clearly compromised waterproofing membrane under the deck surface.

At best guess you'll either need to demolish the concrete and repair the roof, or possibly grind it to solve the pooling and then build a new waterproof membrane on top of it, with a new traffic surface above that; assuming you still want to be able to walk on it.

  • Would they be able to simply apply a cementitous waterproofing layer over the top of the existing concrete?
    – Bob
    Commented Jun 15 at 13:53
  • "The chief disadvantage is that cementitious products have no give to them probably because cement just doesn't stretch to any degree worth mentioning. They will stand up fine to a head of water, but will tolerate almost no joint or crack movement." Quote from: concretenetwork.com/concrete/waterproofing_concrete_foundations/… Slab on a wood frame; I'd give very low odds of success with that sort of product.
    – Ecnerwal
    Commented Jun 15 at 20:22
  • Joints would be a problem (but also not a wearing surface, so you could always use a more flexible seal for the joints), but unless the slab itself is cracked there should be no movement on the relevant surface? If the slab is cracked, well that's a whole other problem that needs to be dealt with. I only mention it because I've used one (Sikalastic-1K) to good effect in similar circumstances, but I don't know enough to directly recommend it to others. It might also be the particular formulation - there's polymer in that mix that seems to make it more crack-resistant than plain cement/mortar.
    – Bob
    Commented Jun 16 at 4:34

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