Originally Posted by edhead
I am in the midst of a bathroom remodel. When removing the old 1940's tile I discovered it is backed by about an inch of mortar on wire mesh. The tile runs about 4' high with plaster wall above. Originally I was planning on keeping the plaster and just redoing the tile surround.
That's what I'd try to do as well.
I am thinking I won't be able to make up the thickness of the plaster and lathe with cement board and tile.
Why not? The plaster will typically be about 3/4 inch thick, and the lath it's stick to will be at least 1/4 inch thick, probably 5/16". It's very possible that the mud bed you're dealing with was applied directly to the lath. So, if you remove the tiles, your underlying mud bed might be flush with the plaster above. If it doesn't turn out to be, just clamp a straight board to the studs in your wall (after removing the lath) and measure the gap between the studs and the back of that straight board. Then, just have a 2X4 ripped to provide 8 foot long shims of those dimensions. You can staple or nail those shims to the wall to get the fronts of the studs into the same plane. Then, you can fasten a cement tile backer board (or a gypsum based board like Dens-Shield) thru the shims to the studs.
So I thinking I need to pull down all the plaster and green board the room. Is this the right approach? Thanks, Ed
Well, don't use green board in any wet areas, like a shower enclosure. That's cuz greenboard is little more than ordinary drywall with a racing stripe. It's simply not sufficiently water resistant to stand up WELL in wet areas. Dens-Shield or any of the cement based boards would be a much better choice.
Also, any plaster you have above the tub won't be deteriorated more more than 3 to 4 feet above the tub, so I wouldn't remove it if you don't need to. If it's lasted 60 years so far, and still looks good and feels solid, there's probably nothing wrong with it. If it was deteriorating from water damage from a shower, it would look like he11 by now.
If this is a wet area, then I'd continue removing the tiles, and then skim coat the rough looking mortar bed you'll probably have with thin set to make a nice flat and smooth base for new tiling.
If the area of the wall you're wanting to remove tile from is above a bathtub, protect the tub as follows:
1. Put the plug down in the tub drain or put the rubber stopper in and apply strips of masking tape across the tub drain in both directions to ensure no bits of ceramic tile or mortar go down the tub drain.
2. Protect the tub and the smooth finish by putting a piece of carpet, pile side down, in the tub.
3. If you're right handed, wear a leather glove on your left hand. Tie a short cord between a cold chisel (not a wood chisel) and the left hand glove. Use a hammer to chip the tiles off the mortar bed. If you drop the chisel, the cord will catch it before it hits the tub and chips it. Also, you can remove the chisel by just taking off the glove it's tied to. And, wear eye protection when doing this kind of work. Someone might bark at me for saying so, but even your own prescription glasses will provide good protection to your eyes when doing this kind of work.
4. You're likely to find that some of the mortar bed will come off with each tile, so your mortar bed is gonna look kinda like the surface of the Moon with all it's craters by the time you're finished. Just mix up some thin set using a little extra of the recommended "additive" (pronounced "adhesive") and skim coat over the old mortar bed with the widest trowel you have. Or, just get a 2 foot wide piece of sheet metal from your local sheet metal shop, screw it to a 1X3 and use that as a large trowel to apply a skim coat of thin set over your mortar bed.
Thin set without any additive in it sands easily when it's first dried, but gradually cures to a pretty hard and durable cement based product over the first few months the thin set is in service. You can EASILY use a sharp paint scraper to scrape off any lumps or bumps in the first and second coat of thin set to get the wall approaching something called "smooth" and "flat".
I've never pulled tiles off a mortar bed, but I've had more than my share of experience pulling tiles off plaster walls that had been set with mastic. Some times the tiles pop off easy, other times it's like fighting with a bear to get each one off, and most often you see both in different areas around the same tub.
But, what you'll find is that even if the tiling was leaking, the plaster will only be deteriorated for about 3 feet above the tub. Generally, any plaster above that will be in pretty good shape. So, even in the area surrounding the tub shower, the plaster higher than 3 or 4 feet above the tub will be in good shape.
If you do end up tearing all the mortar and plaster off the walls around the tub, don't put up greenboard. There's a much more water resistant panel intended for wet areas available from Georgia - Pacific called "Dens-Shield" and it would be a much better choice than green board in a wet area.
For that matter, the only place you wanna put up green board is in the dry areas of your bathroom, where ordinary drywall would be sufficient. I'd just prime that greenboard or garden variety drywall with an interior alkyd primer before painting to provide some degree of protection against moisture.
I'd also use Dens-Shield behind the toilet tank, OR apply multiple coats of interior oil based (alkyd) primer to the wall behind the toilet tank before painting.