Installing durock [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-11-2010, 07:47 PM
I've read some of the other posts about durock installation, but am still confused. I've framed out my shower area, (was a former spa tub area) covered the framing with 1/4" plywood, primed the plywood with oil-based primer, then 2 coats of Red Guard. Two of my walls are newly framed with the plywood. The 3rd wall is an external wall with existing drywall that I intend to cover. I just clicked on to double check before hanging my durock... now I'm finding others who are using felt or tar paper behind durock, painting membrane on top of durock... Help! What are the correct next steps? Also, once durock is up, do I need to tape/mud seams. I was expecting to move on to thinset and tile. I've never taken on a project like this... thank goodness for the internet and your forum!

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02-11-2010, 08:26 PM
Susan, I'm not sure where you got the idea of using plywood in your shower. I know it will be a waste of Redgard but i would take it all down and nail the CBU right to the studs. The tar paper can go up first or either more Redgard over the CBU, either way.

02-11-2010, 08:46 PM

Sorry you didn't find us sooner, could have saved you some time & $$$.

You should do as Davy said. Take the plywood down, install the Durock, tape seams etc., then apply the membrane over the entire surface, at least up to the shower head or so. A surface membrane is the best way to waterproof. Skipping surface waterproofing and just applying tarpaper on the studs do not waterproof anything. It only acts as a vapor barrier.


02-11-2010, 09:24 PM
ok, this is a real bummer! My neighbor recommended the plywood over the durock to add stability. My studs are on 16". Having coated all the plywood with oil primer and the red guard, are there bad consequences to just continuing with durock and another layer of red guard?

02-11-2010, 10:12 PM
Welcome, Susan. :)

I've framed out my shower area, (was a former spa tub area) covered the framing with 1/4" plywood, primed the plywood with oil-based primer, then 2 coats of Red Guard. Two of my walls are newly framed with the plywood. The 3rd wall is an external wall with existing drywall that I intend to coverI think we need to know more about just what you've built and what sort of shower pan or receptor you have or plan for this shower before we go a lot farther.

But I agree with the others that the plywood is a bad idea. It will move with changing conditions in the wall cavity and could eventually buckle enough to cause trouble with your tile installation. The waterproofing membrane on one side is likely to exacerbate that problem.

And unless you have terminated the plywood inside the shower receptor, the waterproofing will not direct the anticipated moisture to the right place. But worse than that would be if you did terminate the plywood inside the receptor. And even more serious moisture problem will exist in that case.

Tell us more about what you have and we'll tell you more about what you need to do. But that will be in addition to removing the plywood as has already been suggested.

My opinion; worth price charged.

02-12-2010, 06:42 PM
Thanks so much for your help! I'm really freaked out now, but will try to explain exactly what I've done. The area previously held a 2-man spa tub that was framed front to back into a 90in space with one side against a exterior wall. The walls around the tub were drywall. I framed in the front and back walls (with studs on 16")to reduce the length to 60". I did not remove the drywall, but framed out with new studs matched up to the existing studs. On the exterior wall (the side of the tub/shower area), I've not touched the drywall and intended to put durock right over the drywall. After framing, my neighbor recommended covering the studs with 1/2" plywood that would add stability behind the durock. Knowing that durock can be porous, I painted oil-based primer then red guard closing all seams and joints (wall to wall) tightly. I also framed in an 18" bench. The shower and bench width is 48". The top of the bench is covered with 2 layers of 1/2" plywood. No, I'm not heavy!! but wanted to be sure that everything was solid. The curb is built with 3 stacked 2/4s. I've not yet started on the pan yet, but intend to use deck mud to build the slope, then cover with Noble chloralide membrane, then finish mud. I also put in the Noble drain with weep holes. Hopefully, I've given you a clearer picture of my work so far

I'm still not sure why the waterproofed plywood is a problem... is it that the durock needs ventilation behind it? Removing all the plywood will be a lot more difficult than putting it up because of course I carefully filled all screws with paint and red guard. Is the durock stable enough against studs that it can't be pushed through? I'm thinking of a bad slip in the shower could break right through it. Also, what about the bench? Is durock alone enough, again on 16" spaced 2/4 frame? I was taking such pride in doing this myself... now maybe I need to call one of those HGTV shows for a rescue!?!
Thanks again for any further help and direction.

02-12-2010, 07:49 PM
Hi Susan, wood tends to swell and shrink with temperature and humidity changes. You really don't need that happening behind your tile walls. You may never have a problem with it if you tile it like it is but it will be much more expensive to remove it later if you did have problems. We try to avoid problems before they happen.

The 1/2 inch cement board is strong enough, it won't cave in.

Houston Remodeler
02-13-2010, 02:17 PM
If you have concerns with the 1/2" cbu, you can always add additional framing either hroizintally or vertically.