Durock cementboard seams

[Guest]

I am in the process of finishing up my complete bathroom gutting and reconstruction and have just installed Durock cement board everywhere that can possibly be exposed to water. I am ready to tile.

Question: What do I do to the seams of the Durock cement board? The Durock was purchased in 3x5 sheets from HD and the employee/professional told me to just use thinset. Is this correct?

Thanks in advance.

[Guest]

Re: Durock cementboard seams

Use thinset mortar with an alkali-resistent fiberglass mesh tape, and install the tape at the time the tiles are being installed--spread the thinset for the tile, press in the tape, and install the tiles. this method results in the lowest , smoothest surface profile. Filling them ahead of time, since backer boards do not have a tapered edge, usually results in a slight hump.

[Guest]

Re: Durock cementboard seams

MB, if you press in the tape after combing out the thinset, won't that give you an inconsistent layer of mortar there under the tile? Or maybe interfere with the full adhesion of the tile?

[Guest]

Re: Durock cementboard seams

The tape is actually open-mesh fiberglass tape that thinset passes through readily.

I used to apply the tape first, then spread the thinset, but the teeth on the trowel tend to snag on the mesh, so I place the mesh after spreading.

It has never seemed to interfere with the adhesive bond in the 20 years I have been doing it.