Questions: Shower tile re-do

[whitemerlot]

I think you should have a contractor out to ask those questions to. Some of them get pretty good discounts on materials, too so you might not even be saving money buying the tile. Our contractor charged us so little to demo that it wasn't even worth the bother for us.

[FoxInFiji]

Whoa whoa whoa! You DO NOT put drywall under tile in your shower. You hear me? Never ever.

I have to get back to drywall mudding and painting but I'll tell you everything you need to know and more when I get a chance.

[hollymichelle]

You would use Durock or Hardie Backer, not drywall.  Also, you'll use thinset to adhere the tile, not mud.  You have to have a waterproof membrane.  You have a few options there.  I don't recall the brand name but one you roll on to the cement board like paint, and another is called Kerdi that's like a film that covers the cement board.  The old fashioned way is 6 mil plastic behind the cement backer. 

[FoxInFiji]

No you only use the green drywall on non-tiled surfaces of the the bathroom like the walls. Green drywall should not be used on the ceiling because it isn't as structurally sound as white drywall. You should always use a cement board product under tile like Hardiboard, fiber cement board, Durock, etc. Note a lot of people don't even use green drywall because it has little to no benefit over using regular drywall but we used it anyway just to be safe. You should still use a high quality paint that is meant for a humid environment and have a good exhaust fan on a timer.

1. Can we re-do only that one side? No the entire shower area is a system and there is no way to waterproof the seam where the new meets the old without taking off the tile on the other walls.

2. How do we make the basement foundation wall waterproof and warmer? If you are going to the steps to do this are you doing the entire wall/basement? That would be best. I would start with finding out what's in your walls right now and go from there. You'll want a vapor barrier and closed cell insulation. There should also be a vapor barrier or pressure treated lumber used for the bottom plate (piece of wood used for the bottom of a stud wall in this case on the cement floor) but that would be hard to correct if you're only doing minimal work. Here are some good articles for basement wall insulation.

3. Do you have to mud the drywall underneath tile? Like I said no drywall under tile. Drywall can not get wet. If it does it gets destroyed and promotes mold growth (see every home that's ever been flooded and the drywall is cut away to above the water line). You use cement board which is much harder to cut and hang. It's also much heaver and every screw (make sure to use the special cement board screws!) needs to be countersunk. I do not like the foam filled cement board because it dents easily though it is lighter. If you don't have experience with this I would hire your tiler to hang the cement board that is what is normally done. It's hard, messy work and much less DIY friendly than drywall. The seams of the cement board should be "mudded" with thinset. I could go into explaining modified vs unmodified thinset but it sounds like you'll be hiring out the tile work so like I said I would suggest hiring out the cement board as well.

OK shower wall waterproofing 101. Back in the day roofing felt would be stapled to the studs behind the cement board and overlapped. There was still an air gap and therefore no vapor barrier. That was all the waterproofing there was. Today in a lot of builder grade homes the same set up is used only it's a sheet of plastic or sometimes a rubber membrane stapled behind the cement board. Still not very good. Modern waterproofing techniques are better because they waterproof over the cement board keeping the cement board from ever getting wet. Unlike drywall cement board can get wet but it can't stay wet. If it stays wet it turns soft and mushy and leads to cracked tiles and grout or worse. For this reason if traditional waterproofing is used there always needs to be weep holes at the bottom of the wall and everything needs to be carefully layered to allow water to drain out of the cement board. Modern waterproofing involves two different styles. The paint on (Hydroban or Redguard) or the thinsetted on rubber membrane (Kerdi). The paint on is much easier IMO because it doesn't add a lot of thickness at the seams and corners like the rubber membrane does which needs multiple layers. That added thickness makes it hard to tile over. But since you aren't DIYing it your tiler can use whatever type they like as long as you ask for the waterproofing to be on top of the cement board. Also note a lot of tilers will use the plastic sheeting behind the cement board and then put a layer of paint on only over the seams of the cement board which is better than nothing but still not as good as painting the entire cement board. It's worth noting that the paint on type are water barriers but not vapor barriers so a vapor barrier should still be in the wall. The rubber membrane style is a vapor barrier (and the only type of waterproofing that should be used in a steam shower) so you should not have a vapor barrier in the wall behind it. Never sandwich materials between two vapor barriers.

4. Someone in another thread recommended some kind of mildew resistant grout and maybe even silicon. There are many cementious grouts that have additives to help prevent mildew and staining. You can also buy the additive separate and add it to some grouts. In real life though they only delay the growth of mildew and staining. You still need to seal them every 6 month - 1 year to help prevent staining and clean on a regular basis to help prevent mildew. (A good exhaust fan on a timer also will make a big difference on mildew growth. If you don't already have one of those I suggest adding one.) If you truly want no staining and make it difficult for mildew to grow you should go with epoxy grout. It is not porous like cementious grout and is waterproof. It never has to be sealed. It costs more and the labor is more intense but if those things are important to you (and you plan to be in the home for a while) it's well worth it. Here's a post I did about it:
threeacres.wordpress.com/2012/03/02/diy-epoxy-grout-its-really-not-that-hard/

As far as silicone goes 100% silicone caulk should be used instead of regular caulk at change of plans or intersections between tile and wall/ceiling. Your tiler should do this for you.

HTH

[FoxInFiji]

Jan 27, 2013 9:42:57 GMT -5 asdfjkl said:

No, I know you don't use mud to adhere tiles.  I'm talking about whether it's necessary to mud the seams of the drywall (greenboard) if you're going to be putting tiles over it. 

I guess my questions must not be very clear, but I know what I'm asking in my head so maybe it would be easier for me to just use the google to find my answers.

I think I made it clear in my last couple posts but just in case here's a picture of our alcove tub and shower (that is what you are describing).



Cement board on all of the shower walls.  Thinset the seams. 

Green drywall on regular (non-shower) walls with drywall mud seams. 

We ran our bullnose tile just outside our tub to help with any splashing or water that comes off the shower curtain so our cement board goes a little past our tub.  Seen here: