Hi! This will be my 2nd time building a shower pan using the directions from this web site. My question is regarding the step where you install 2x10's in between the studs so the rubber membrane can be attached to it. My friend's shower opening has blocks on 1 side and the other 3 sides are already framed in. They have 2 layers of 2x4's on the base. Is it still necessary to use 2x10s on the 3 sides? And is it ok to apply the rubber membrane directly onto the block using adhesive? The way the shower is layed out, it would be extremely tight to fir out that wall with studs. The wall is in a basement on an exterior side. Any suggestions would be appreciated. Thanks, Amy

You can use any size 2x that you want, as long as you can stack it up high enough to get a couple of inches above the curb..

As for that exterior wall, how are you putting the tile up there? There has to be something to come down over the liner to stick the tile to.

You can frame it with 2x4's laid flat, so you would only lose 1 1/2" of space. You'd probably need to get some Tapcons or something similar to attach them to the block wall.

Duh...wasn't thinking about not being able to tile over the rubber membrane on the cement side. Do you think it would work to use a heavy adhesive to glue tile board to the cement/block wall? Or, if I use the lowest power caliber with my trigger drive do you think it would go right through the cement/backer board?

If you glued it, my concern would be the moisture getting to it and the glue releasing.

Keep in mind that if you do manage to get it glued up there, you'll have to use a surface-applied membrane to keep the moisture out of it. Liquid or sheet will work.

If you don't plan to use either, you'll have to put some 2x's up there, hang 4 or 6 mil plastic, then your CBU.

Personally, I wouldn't trust the glue, and I think anything you try to 'shoot' through it will cause the CBU to crumble, which will compromise the hold.

I would recommend the following process: Use a thin layer of construction adhesive to Glue the liner approximately 6 to 10 inches up the cement block wall. Then use thinest spread on with a 1/2 inch notch to glue a sheet of GreenE board on the whole wall You can Brace it in place while the thinset sets up or shoot some fasteners in it. The green E will overlap the liner and also hold it in place. Then water proof with a liquid membrane or Kerdi.

You should still use something for backing a the bottom of the framed walls. 2x8's will get you to a good height wince it's already built up a bit. This gives the drywall or cbu good backing and also allows you to staple the liner well above the curb line.

You could also use a Schluter drain and forget about the whole pre-slope/liner thing. Just build one mortar bed and waterproof the whole thing with hydroban, aquadefence, or redgard.

If this is a basement below grade wall, you DO NOT want any conventional tile backer directly attached to the block wall. Moisture transmission will ruin it within one year.

The only product that would work is Wedi board. It is totally waterproof on both faces and can be thinsetted directly to the concrete block. And its also has a thin layer of insulation foam to act as a thermal bridge between the concrete and the interior of the room.
The Wedi has the ability to be notched for your pan liner.

You only have two choices, fur out the wall and use a conventional tile backer or use the Wedi board.

Thanks for the responses. I'll let my friend decide which route to go. Personally, I'd build the stud wall. We have all the supplies and I've done it before. One more question...If I use the waterproof membrane behind the stud wall,do I still need to use a liquid membrane over the cement board, before I tile? The place that sold me my tile told me their installers always use the liquid on every surface before tiling. Is this necessary?

Can you elaborate on that detail? Is this method from your tile shop?

The tile store wanted to sell me a gallon of this black liquid waterproofing material. He said that you should always apply this onto the cement backer board before tiling, whether it's an interior or exterior surface. I had never heard of this before.

The tile shop is correct. However that has nothing to do with your statement about a membrane behind the stud wall.
Who is actually doing the work, you or the tile shop?

My neighbor and I are doing the work. She has settled on building a stud wall on the block side of the shower wall. We are going to put a plastic vapor barrier up as well as insulation before we attach the cement board.

So, back to the liquid waterproofing...Do you always use this on the cement board before you start tiling? I didn't do this with the shower in my basement. I just started tiling with thinset after I built the shower pan(followed directions from this website) and walls.

A reputable tile setter would recommend a topical waterproofing as standard practice or as an upgrade option. Whether its cement board doesn't matter. It's just good practice to waterproof.

Depending on the brand of liquid waterproofing your planing on using will determine if the poly barrier should be installed over the studs and insulation. What you do not want to create is what is known as a moisture sandwich.

Thanks for all the info. I've learned a lot! Amy