Not so perfect shower drain.

Hello everyone,

I am currently installing a standup shower in a room that did not previously have a bathroom. When I put the shower drain in, I forgot to compensate for the 1/4" cement board wall and now the drain is no longer perfectly centered. Is there a specific fitting made to fix this or do I have to rip up the cement and put a new drain line in?



Thanks for your help.

 

You do not need the cement board behind the shower base. You want the base, like a tub against the 2x4's so there be no chance of water working itself behind the shower base. The cement board should overlap the base back edge to about 1/4 from the curb of the base. You then tile to about 1/8 of an inch from the base curb. If the cement board flairs out too much so the wall is not perfectly straight (vertical), you can make a rabbit cut behind the edge of the board so there is a nice overlap. However, with wood stud walls nothing can be perfectly flush so the thin set for the tile would make up for it.

 

INdustry standards call for either a moisture barrier behind the cbu, or waterproofing on top of the cbu. Cbu isn't damaged by being wet, but it is not waterproof and can transmit moisture through it. If you use the moisture barrier behind, you want it to lap over the tiling flange so any possible accumulation will drain into the shower rather than in the wall cavity.

To help make the shower pan last longer and 'feel' better, often, it helps to set it in small piles of mortar. This does two things:
- helps you get it all level
- helps firm up the bottom so it doesn't deflect.

To work well, you want the riser coming into the drain of your pan to be plumb. IF it is offset more than a small amount, it may not seal well, or, if you bend it, the stress, long-term, could cause issues.

 

Also, once the pipe is centered in the base, if needed you can fir out the walls so the cement board overlaps the base flange without bowing out.

I would not use the plastic behind the cement board but would use redgard roll on membrane. Works well and it prevents the cement board from sucking moisture out of thinset.

 

You need one or the other (moisture barrier behind, or waterproofing on top)...not both.

If you're going to use RedGard, follow the instructions for use over HardieBacker...you must thin the material for the first primer coat. Then, once that dries, follow up with the required two full coats, letting it dry fully in between.

Building a proper shower isn't hard, but it is detailed...you must not skip steps, or mess around trying to reinvent the wheel. The TCNA guidelines list many ways to build a shower, pick one, follow it, and you'll have success.

 

Thankyou everyone for the help. I now have a better plan for the shower install. have a great day!