Need some enclosure design help....

[Breven]

I think you treat cement board and cement block the same, right Jim?

[dmun]

When I tiled the interior of my chimney, I just slathered thin-set with a trowel on the bare (dampened) concrete block, and slapped the terracotta tiles up. It's not as flat as a billiard table, but boy are those things stuck tight.

Buy the cheap stuff, unless you need the white for translucent stuff like white marble tiles. DO NOT buy the stuff which is "Fortified", it is impossible to mix smoothly and hard to trowel on.

And by the way, I don't think this is recommended, but my concrete blocks were not exactly flat, and I just slathered the stuff on more thickly to compensate for it. Seemed to work fine, although not as good as a proper scratch coat, I'm sure.

[CanuckJim]

Dmun's right on the money. Thinset works very well on block, too. I've had to use a thick coat at times with no problems. The advantage is the stickiness of the product. The pics I posted might be a bit misleading. The stones were shimmed with 3/8" thick pieces of wood. Around here, that thickness of pointing line is traditional. Once the Thinset cured a bit, I pointed it with a 3:1 mix of brick sand and Type S. That's the look I prefer, and if no shims are used, be careful about how much you lay up at once. The shims balance the weight; stone on stone can create bulging problems if you put up too much at once.

Jim

[Breven]

Dmun-

What is a proper scratch coat? The round wall at the back end of my oven is very uneven (square blocks can't make a perfect round shape) to compensate, I was just going to slather on the thinset really thick where I needed to. Maybe I should fill all that in right now with a scratch coat? If it si what I think it is....