How do you treat the joints when using 1/2" durock to make a hearth?

[JPapiPE]

My hearth will be 2 -1/2" layers of micore and then a 1/2" layer of durock, then tile. I need a 4'X4' hearth according to specs. With an R value of 2 or better. How does one treat the joints in the durock, as this stuff is only sold in 3'X5' sheets. Do you just joint compound mud the joint with no tape? or what? I suspect paper drywall tape or mesh is treated as a combustible.

 

[Jags]

as this stuff is only sold in 3'X5' sheets.

Not true. It is also sold in 4 x 8 ft sheets in both 1/2" and 5/8".

 

[Shane]

I used to just use thinset and let that set up. I think that's what they recommend on large floors etc.

 

[Tfin]

as this stuff is only sold in 3'X5' sheets.

Not true. It is also sold in 4 x 8 ft sheets in both 1/2" and 5/8".

I concur.

 

[Highbeam]

I also used two layers of durock with an oversized hearth so I had butt joints to deal with. The durock folks sell a special joint tape-fiberglass type mesh that is alkaline resistant. It is applied like sheetrock tape and you use thinset mortar as mud. The durock is actually concrete with a net of the same fiberglass fibers so just like the paper in the sheetrock, the strength is in the mesh. You must use the mesh to maintain the strength.

 

[Jags]

The tape is actually called...get this.....Durock tape. It is a mesh tape that can be purchased in 2" and 4" widths and are 75' and 150' long, respectively. The 2" wide is typically used in interior applications and the 4" is for exterior.

 

[JPapiPE]

No S**t Durabond tape. I'm learning something every day....thanks for the tip

 

[Jags]

No S**t Durabond tape. I'm learning something every day....thanks for the tip

No. Not durabond, that is for drywall. DUROCK.