Tiling over gypsum lath

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Old 12-01-12, 08:13 PM
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Tiling over gypsum lath

My house was built in 1940 with what appears to be plaster over gypsum lath. I'm remodeling the bathroom and I need to tile the tub surround. The back wall of the tub surround has the plaster/gypsum exposed, while the two ends are simply drywall. It looks like the gypsum is in pretty good shape but a good bit of the plaster if breaking/falling off. Can I apply thinset directly to the gypsum lath and tile over it? I'd really prefer not to tear out the wall and lay cement backerboard because the gypsum lath seems to be in good shape and looks like a pain to tear out. The top third of the wall (plaster, lath, and all) is in great shape, the middle third of the wall is in decent shape with some of the plaster falling off of the gypsum, and the bottom third of the wall is exposed gypsum with some drywall "patches". I'll try to post pictures, if I can, tomorrow.

I am a first time poster, first time homeowner, and first time DIYer. Any help would be much appreciated. Thanks.
 
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Old 12-02-12, 03:36 AM
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Welcome to the forums! You are doing a once or twice in a lifetime remodel. Let's do it right and take it all down to studs. I know it is a PITA to pull down all the lath, etc. but you will not have an adequate substrate for tile by using the plaster alone. With the pix, we can tell a lot more about the situation, and may offer alternatives. Is the tub already in place?
 
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Old 12-02-12, 04:37 AM
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Thanks for getting back to me so quickly. The tub is already in place and seems to be in decent shape. It's a cast-iron tub and would also probably be a PITA to remove. The rest of the bathroom has been remodeled numerous times with drywall hung over the lath. If the gypsum needs to be removed, then that's what I'll do. I'll try to get a picture up later today.
 
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Old 12-02-12, 07:27 AM
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The fact that the plaster is already falling off tells you that it will probably fail when you try to hang tile on it. As Larry mentioned, there is no substitute for doing the job right the first time. I assume that there in not a shower associated with this tub.
 
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Old 12-02-12, 03:43 PM
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Update: I removed the back wall with the plaster and gypsum lath. There's still some lath in the corners because there was wire mesh buried in the gypsum there and I was having a difficult time getting it out. The two ends of the tub are drywall and I'm trying to prevent from having to remove the drywall. I want to do everything right but I also need to do it on a budget and do it quickly (it's the only bathroom in the house and it needs to be ready soon so that we can move into the house before our current lease is up).

As for the exposed wall, I purchased hardi-backer board but I'm contemplating whether I need to put up green board first. There's a good possibility I'll be calling a contractor to get an 'official' opinion on what needs to be done and what it would cost to have someone else do it.

Thanks for all the help and any further advice will be much appreciated.
 
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Old 12-02-12, 05:06 PM
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If you are tiling, remove all the sheetrock in the tub area. Cut vertically where the color changes at the edge and replace it with 1/2" concrete backer board (hardie/durock, etc.). Let the cbu come to the top of the lip on your tub. Your tile will extend down below that and close the gap without problems. I know it sounds extreme, but you gotta do it right. You don't want greenboard, or sheetrock in a potentially wet area like this.
 
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Old 12-03-12, 05:17 AM
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Looks like they had a glue up plastic surround on it at one time, which explains the drywall. If you are going to tile, would really prefer you go the extra now that you have gotten this far and remove the drywall front and back of the tub.

Put up 15# felt as a vapor barrier, start low and work up overlapping the joints of the felt. Then hang your backer board and tape all seams and corners with mesh tape and thinset mortar. You will also want to bridge the gap between where the new backer board meets the drywall. Do this using joint compound and drywall tape. You are then prepped for tile.
 
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Old 12-03-12, 05:24 AM
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I prefer to use a setting compound like Durabond when taping the joint between the cement board and drywall because it's not water soluble like regular j/c is.

Is that mold on the backside of the drywall?
 
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Old 12-03-12, 04:38 PM
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Thanks for all the advice. If I do it myself and keep it a DIY project, then I'll remove the drywall at each end and put up 1/2" hardi-backer or cement backer board. Unfortunately, I'll have to call a contractor or someone to do the floor so I'll see what the estimate is for the tub as well. I'll post more photos in the future as work continues.
 
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Old 12-04-12, 02:51 AM
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Be sure to insulate and apply a vapor barrier ahead of the cbu. Why do you have to call in the pros for the floor? You got us All we need is your back and hands.
 
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