mesh drywall tape swelling from moisture

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Joined: Mon Mar 05, 2012 3:01 pm

mesh drywall tape swelling from moisture

Post by Haka » Mon Mar 05, 2012 4:04 pm

I have a butt joint ceiling crack next to the shower. The crack is at least 4 ft long and maybe 3/8 of and inch at its widest after opening it up and cleaning it out. The ceiling joist run perpendicular to the joint. I repaired the it using fiberglass mesh tape, first filling the crack with mud and then embedding the tape. After applying a second coat of mud and letting it dry I took a shower in that bath again and the mesh tape swelled/ridged up along and parallel to the crack (at times shifting from one edge of the crack to the other edge with no connecting ridge between the 2 edges) about an eight inch wide and high enough to both feel and see clearly. A while after the room dried out the ridge would flatten out pretty smooth though you could still see it. So stupidly figured that I had not set the mesh tape into the crack properly, and decided to put a second piece of mesh tape over the first and stretch it out tight to hold the ridge down. Feathered it out, lightly sanded it, looked great, and primed it. Went back to taking showers in that bath, and the ridge reappeared with the first shower.... Tore the whole thing out and started over, still thinking that I had not embedded the first mesh tape properly in the mud.
Re-filled the crack, and embedded mesh tape solidly into the mud and crack. Put on second coat and finish coats of mud, looked great, much better than the first time. Didn't prime and took a shower, you got it, the mesh ridged again just along the crack. Both the first time I tried this, and this second time, I allowed a full day for drying between applications of mud. I used different kinds of mud each time, the second time using a VG quality joint compound. I sanded off the top layers of mud to the point where I can clearly see the outline of the mesh tape, no apparent flaws, it's beautiful and flat. So I am considering trying to put a piece of paper tape over the mesh that is there, thinking that it will both provide a moister barrier and strength to the prevent mesh from swelling. I'm not worried about the thickness, I know I can feather it out to disappear.
Am I being stupid again or will this work? OR should I just tear it all out and start over? Why is this fiberglass tape doing this?? I have worked with mesh tape many time in the past, there is even some other wall spots repaired with the same mesh tape in this bathroom, and never experienced anything like this, but then again I wasn't working on a ceiling space right next to the shower.

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Re: mesh drywall tape swelling from moisture

Post by Shannon » Mon Mar 05, 2012 5:29 pm

Welcome "haka" This is a very odd problem. I do not use mesh tape much myself but I almost do not think it is the tape.Is it possible that the moisture from you showering is causing the drywall to move or something that it is attached to?(even as I read this back to myself I almost can't believe that would be the case!) I'm only thinking this because you say it almost flattened out after the room dried out later on. I really can't see the tape swelling,the product it is made from should really not absorb any moisture especially once it was primed and painted. Look at the other variables involved in the ceiling of that room,Im convinced something else is swelling and moving. Please let us know what you find! This is puzzling me.
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