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We got called back to a house our company built 10 years ago because of an extensive leak in the master bath shower. We removed all the tile and floated concrete shell and discovered that the cause of the leak was an unflashed shower bench. Originally we hoped that the rot would be contained to the lower half of the shower walls, but we found that the whole wall was rotten– all the way through to the plywood sheeting. The shower is in the exterior corner of a stuccoed house. Even though we had to remove ALL the framing and plywood sheeting, miraculously enough the exterior stucco still stands uncracked. So we have a few questions…
1) Since the only leak was at the bench (16″ high), could condensation (warm steamy water entering the wall cavity condensing on the cold exterior wall) be blamed for severe rot all the way to the top of the wall cavity? This leak is probably 10 years old.
2) Ok, we are really hoping to save the exterior stucco. We have considered gluing pressure-treated plywood to the stucco, adding framing to the inside, using cleats to attach the two. Should we use Gorilla Glue, construction adhesive, or some type of thinset morter to attach the plywood to stucco? Or would the diffeence in the expansion rates of the wood and stucco cause the stucco to crack?
Thanks for any help you can offer! –William, Portland, OR
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This is advice from a plasterer not from a builder or engineer so take it for what it is worth.
1) I don't know if condensation alone accounts for the rotting of frame and all. Is there any possible exterior source for the moisture?
The fact that the stucco is still standing speaks well for the stucco; however stucco is not meant to be self supporting. I am guessing that the stucco is over woven wire rather than diamond mesh galvanized lath. Is there asphalt felt inside the stucco? If so what kind of adhesive will stick to that?
2) I think some attachment to the stucco is good for both the wall and the stucco. I think you should rebuild the wall from the sill up including something to replace the thickness of the plywood sheathing but don't rely on the stucco to hold the wall up. I also think a few mechanical fasteners from the outside into the new sheathing and/or studs is a good idea. Adhesive is good if you can find one that will hold. I hope you can either replace or left intact the asphalt felt and it still bothers me that you want to try to adhere to that hence the mechanical fastenters from the outside in. There will be some holes to repair and to get any bearing on the stucco you really ought to use some kind of a washer such as plaster washers. I think you should remove a little of the stucco finish say 1/8-1/4", install the washers and screws they will be countersunk, then be prepared to patch and maybe even refinish the area but not replace it.
Please let us know what you do and how it works.
John McElwee