Plaster vs sheetrock on tiled bathroom wall?
Hi We are remodelling a bathroom. Our contractor wants to rip out the plaster walls so he can put in some kind of waterproofing thing behind new sheetrock. I know the consensus on brownstoner is never to replace plaster with sheetrock but (a) these walls will be tiled, either to ceiling or to 54″. (b) the three plaster walls are external. I believe sheetrock can offer significant insulation improvements in this situation. Is removing the plaster really so bad, and if so, why is he recommending? Does it save him time / money? Or is this waterproofing stuff important? (i see no problems with the existing walls, but they are behind some kind of crappy plastic covering the last owner installed). Oh and there’s very likely lead in/on the plaster, and we have a toddler. thanks.

pocketdora
in Roofers 10 years and 11 months ago
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greenmountain | 10 years and 11 months ago
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Plaster in a bathroom is fine. It insulates better than sheetrock, especially with wood lathe, and is more long lasting in wet conditions, and repairable. I often patch it or replace small wall segments using lime and plaster of Paris finish (Diamond veneer coat) over perlited plaster rough coat (Structo-lite). I can tile over it, but it is often not flat enough. I prefer to preserve the crazy, wavy wall shapes in old bathrooms made with “wet wall,” where reasonably possible. I don’t like the visible seams and joints in regular dry wall panels, especially ugly when plaster and sheetrock are combined. If old paint is loose, or plaster with lead paint will be demolished (1 sf or more), the EPA lead law applies. Use an EPA certified painter or renovator. Many coop managements insist. Two strategies exist regarding tile substrate in showers, tub surrounds, and surfaces intended to become wet during normal use. First, sheetrock with purple, green or other paper covering, provides food for mold, which will appear as long as there is also water and air. It just takes longer with the mold resistant colors. Carri1 and Dave suggest using cement board because it maintains its shape and strength (more or less) when it gets wet. Cement board is inorganic (no paper), so it is not nutritious, but if it is attached to wood studs, and water soaks through cement board, mold will feed on the wood and thrive in wet porous cement board, cement tile mortar and cement grout. A few of the steel screws, when holding wet cement board on to steel studs, eventually rust and lose their grip, even without mold. The second strategy, which I subscribe to: Why allow any of it to get wet, when waterproof membranes have existed for decades and are increasingly available? This way initially costs more, but quickly preserves your investment. Only waterproof membranes will prevent mold and protect substrate. You can use sheet rock with tile in bathrooms, or cement board, but both should be kept dry. Cement board is heavier, harder to cut, harder to repair, and comes in panels so small, you need many of them for a bathroom. After installing sheet rock or cement board, I cover with waterproof Kerdi fabric, though some people prefer roll on liquid membranes. For more insulation, and fewer steps, I sometimes use waterproof tile substrate. The waterproof fabric comes attached to both sides of rigid foam. You can’t use it without tile. I can carry 10 panels of waterproof Kerdi Board up 4 flights of stairs, in one trip, and cut them with a knife and t-square. If I can’t make the stairwell turns with 1/2″ x 4 x 8’s, I can manage with 48 x 64″ panels. With the membrane applied in advance or on site ( or some of both) the substrate stays dry. When waterproof membranes are installed in tub surrounds, or tiled showers, all the water goes down the drain. Isn’t this a more simple way? Cement board is more complicated: Some of the water goes down the drain, but it prevents damage from the rest of the water, or at least reduces the food supply for mold, which continues to live inside wall cavities, if the studs are wood.

daveinbedstuy | 10 years and 11 months ago
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It is essential that a waterproof backing be used behind tile that will be exposed to water in a tub or shower. Traditionaly that is accomplished with Durock (cement board) over the framing. There are newer technologies now that employ membranes over greenboard (Schluter, RedGuard, etc) but most GCs aren’t educated about these systems and just want to do it the old way with cement board and thinset mortar, which is still fine.

carrie1 | 10 years and 11 months ago
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I have been a general contractor in Manhattan and Brooklyn for many (over 25) years. Never tile over Sheetrock in a bathroom. It does not matter if it is green board it will quickly become an unsound substrate. The very least you should use is wonder board(cement board) anchored and glued to the brick( it should be plumbed and squared with all corners & joints properly taped-when you start to tile you’ll know why squaring and plumbing is important). The reason your contractor does not want to keep the plaster is because he or she most likely does not know how to skim over the plaster with cement(an actual skill) & is going to attempt to laminate sheetrock by putting spackle behind it and tacking it to the brick. Tile over Sheetrock is always an inferior job. If this is a home you plan on living in for more then a few years I would suggest doing a nice skim job(no need to remove the plaster)& it will last a life time.

brokelin | 10 years and 11 months ago
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The toddler is not an issue with leaving the plaster – as lead paint covered with non-lead paint that is not chipping off is also not a problem – it is safe. The lead dust that will be created by taking out the plaster walls will put lead in the air while it is being done and before the lead dust is well cleaned up afterwards. The place where just painting over old lead paint continues to be a problem is only where there is friction that wears away at the new paint, exposing lead dust from the paint lower down – this being where doors close and open on the wood molding and where wood painted old windows move up and down. Windows are often replaced, so no longer create a problem then. People get all upset about old walls, which are fine when you paint them, yet don’t strip the door and molding around it, which is where lead can be a problem if there is friction rubbing off the new paint. I haven’t done this sort of work, but I don’t think tile over plaster would create any problem where there is just wall – it really doesn’t get that wet. Only in the shower area is there significant water on the wall. I have lived in very old buildings (100+ years) where tile was added to the shower area over the original plaster walls, and there was no leakage through the tiles. My last place had plaster walls from the first decade of the last century, and the bathrooms were all redone in the 40’s, so had tile that was put on the wall – most of the way up in the shower, and halfway up in the rest of the room, and there was no water damage. That tile was secure on the wall, the grout was firm, and all was well. I suspect the tile was added in the 40’s when I suspect the shower was added – it definitely was not newer than that, as the entire large building had its bathrooms done with identical elements then (it was still a rental with one owner in the 40s). I suspect that they added some sort of barrier behind the tile over the plaster wall, as the tile stuck out further than just tile on the wall would – but they definitely didn’t remove the original walls, as they were still plaster above the tile. If you are concerned about creating lead dust unnecessarily by tearing out plaster walls, and if you have someone tell you that plaster will hold up fine, then I’d find out if you can just have a really good old-fashioned water barrier put over the plaster wall (find out what they used back in the 40s for this) and have the tile put in over that.

rh | 10 years and 11 months ago
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If it’s a bathroom, the plaster wall rule can get thrown out. You have to deal with moisture and it is best to use waterproof material behind tile so you don’t have to worry about mold. BTW, if the lead is sealed behind the new tile, it wouldn’t be an issue.