Cement board on hollow core cinder blocks

[Bman]

I am going to do a cast in place (concrete over cement board) hearth on hollow core cinder blocks. My question is how do I anchor the cement board to the block? Can I just use type-s mortar or thinset even?

 

[begreen]

Not sure why the need for cement board then.

 

[Bman]

Not sure why the need for cement board then.

Because the blocks are hollow and it's a cast in place application. If the blocks were filled I wouldn't need the cement board.

 

[begreen]

OK, I think I'm following this now. Mortar should suffice. With the weight of the concrete it isn't likely to be budging once the mortar sets up. Wet the cement board with a spray bottle before setting.

 

[Bman]

OK, I think I'm following this now. Mortar should suffice. With the weight of the concrete it isn't likely to be budging once the mortar sets up. Wet the cement board with a spray bottle before setting.

Thanks, that's what I figured too. I also thought about using landscape block adhesive to anchor the cement board possibly.

 

[kennyp2339]

Thanks, that's what I figured too. I also thought about using landscape block adhesive to anchor the cement board possibly.

Use mortar, landscape glue could be flammable or off gas odors when they get heated