Home>Discussions>EXTERIORS>Ruined exterior gypsum sheathing - repair tips?
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hollasboy
Ruined exterior gypsum sheathing - repair tips?
hollasboy

This is a new one for me. Got a call from a client wanting some water damage repaired from a leak (caused by damage to masonry joints during a window retrofit). I opened a hole in the interior sheetrock and pulled back the damp fiberglass roll insulation, expecting to find tar paper or Tyvek between the studs and brick, but instead found another layer of sheetrock with a brown color. Research showed me "exterior gypsum sheathing" which seems crazy to me, knowing how sensitive any wall board is to water.

This stuff is soaked and crumbling, already completely failed in the spot I checked, with about a 1' x 1' hole open to the back of the brick. The sheet is attached to the studs from the brick side, with only 1" or so of air space, so not sure how to even get in there to either replace it with something better, or close it back up.

Has anyone else ever encountered this problem?

Thanks!

A. Spruce
Re: Ruined exterior gypsum sheathing - repair tips?
A. Spruce

If the damage is on the outside, how do you propose to repair it and keep it water tight if you cannot access it from the outside to apply the layers and waterproofing correctly? If your roof was leaking, would you try to patch it from the attic?

hollasboy
Re: Ruined exterior gypsum sheathing - repair tips?
hollasboy

That's the crux of the problem - there is no way they are going to rebrick their 3 story house. The water damage is at the bottom floor, and from what I can tell, damage is about 10 feet wide. The window that leaked was on the stair landing between first and second floors.

I guess I have several sub-questions about this gypsum board. Is that really a good idea? Manufacturer's website says it is water repellent, but here is a case where it soaked up the water through and through. And once it goes bad, what are you supposed to do?

Clarence
Re: Ruined exterior gypsum sheathing - repair tips?
Clarence

USG had a sheathing that was 2 ft. X 8 ft. 1/2 inch brown paper V - T&G with an Asphalt inpreginated Gypsum core
used as a back up for exterior substrates.
It was water resistant with a specially treated brown water -repellent paper on both sides.
Long periods of dampness would cause the core to fail.
USG stopped making this product around 1985 / 1988.
When used as a backer for stucco it was covered with felt paper.
Brick masons would lay the brick with no water barrier.
The house you are working on was mostly built around 1960 thru 1970.
Spruce is correct remove the brick.

A. Spruce
Re: Ruined exterior gypsum sheathing - repair tips?
A. Spruce
hollasboy wrote:

That's the crux of the problem - there is no way they are going to rebrick their 3 story house. The water damage is at the bottom floor, and from what I can tell, damage is about 10 feet wide. The window that leaked was on the stair landing between first and second floors.

I guess I have several sub-questions about this gypsum board. Is that really a good idea? Manufacturer's website says it is water repellent, but here is a case where it soaked up the water through and through. And once it goes bad, what are you supposed to do?

You really only have three choices here:

1 - Run from this job like your hair was on fire because you're in a no win situation, even if you do the repairs correctly, there is no guarantee of success due to the composition of the wall, however, you touched it, now you own it.

2 - Crap the job together and hope for the best, however, you touched it, now you own it.

3 - Do the job correctly, which means accessing from the exterior, make the repair, then repair the exterior. Yes, expensive, yes a pain in the hind quarters, but it is the only way to get it done properly and assure no further leakage from around this window. Why, you guessed it, you touched it and now you own it, which means, if you're going to own it, you might as well make sure the repairs are done on your terms to your satisfaction.

I do hope that you bid this job as time and materials to do exploratory surgery ONLY, leaving yourself the option to submit a proposal for the actual repairs or refer the work elsewhere, otherwise, I fear you are in for a world of pain, suffering, and doing the job for free for the amount of time you're going to spend on it and the resultant call backs.

Mastercarpentry
Re: Ruined exterior gypsum sheathing - repair tips?
Mastercarpentry

In my time as a lather I installed a lot of this stuff with the carpenter in me screaming "what idiot thought this crap would work?" but they said it would so....

It adds no more structural stiffness than sheetrock. It was used because it met fireproofing requirements for commercial and multi-family construction with metal studding. On wood studs it is insane to not spend a little more for wood sheathing and get a much stronger house in the process but when consumers and builders let the dollar rule this is what you get. I cannot imaging any sane builder using this on a 3 story home where structural stiffness would matter a lot.

Since you can't fix it properly without a full re-do of the brick the only alternative I see is to use sprayed-in foam insulation to restore the questionable air-sealing this stuff provided knowing that all the crumbling junk is going to fall between brick and structure absorbing water and causing everything to rot sooner or later. Or patch the inside and forget about it being sure the homeowner signs off on that as being acceptable on a document recommending the full exterior demo. Or walk away from the job after explaining that it cannot be repaired without the brick re-do which was their choice to not have happen. If one builder did all the houses there then that development goes onto your 'do not enter' list along with any others they built.

Phil

dj1
Re: Ruined exterior gypsum sheathing - repair tips?
dj1

Tell your client that you can't give him a bid price, and you can take the job on labor & materials basis only.

Sombreuil_mongrel
Re: Ruined exterior gypsum sheathing - repair tips?
Sombreuil_mongrel

I used this stuff in 1997, to fireproof a party wall situation in two adjacent houses. The building inspector demanded it; I had never used it before. I'm certain they still manufacture it.
There is no repair, the wall has to be rebuilt. It's no different from water damage to OSB sheathing, that stuff falls apart when it rots too; had to replace a bunch of that under stucco- the stucco got torn off and then patched back. That's the way the cookie crumbles, I hope their homeowner's covers it.
Casey

hollasboy
Re: Ruined exterior gypsum sheathing - repair tips?
hollasboy

Thanks for the background info. This goes onto my lifelong list of construction methods where I just can't fathom why that ever seemed liked a good idea.

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