I’m doing a small amount of tile work around a shower and on the floor in a bathroom. The shower has a fiberglass pan. I put shower liner membrane behind 1/2″ durock and draped both over the tile flange on the fiberglass pan. Now I’m wondering what the best method is for sealing the joints in the durock and around the holes I made for the shower valve and head? I have talked to a few others that have done a lot of this kind of work and have heard of several different methods. The most preferred seems to be thinset with a fiberglass mess tape??? Any advice before I dig into the project?
Also, I read on durock website that they recommend putting down thinset on my OSB subfloor and then screwing down the durock before tileing. Any advice/tricks on doing that? Mostly seems straight forward. Thanks
upnorthframer
“If you think education is expensive, try ignorance!!!”
Replies
Yes, you tape the joints with 3"-wide FG mesh tape made specifically for use with cement board. Don't use gyprock mesh tape; the adhesive is incompatible with cementitious products.
There used to be a special CBU joint compound available, but my local suppliers no longer carry it and everybody (me included) has gone over to using modified thinset with, apparently, no ill effects after 7 years.
As to placing thinset under the CBU before screwing it down, this is mostly to fill any voids that might be created by the ply or OSB not being perfectly flat. You don't have to go nutz, but use a long straightedge to find any bad dips or humps in the subfloor and then do what you gotta do to fair them out. Use a ¼x¼ notched trowel to spread the thinset.
Screw the CBU on 8" centers in both directions. Do not use gyprock screws or flooring screws. There are special screws made for this with an oversized head and a thickened, self-chamfering shank.
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....
I use GE silicone.