And...never use conventional Portland for any situation where the heat may get above about 200 degrees. Fireplaces, chimneys and such require the use of special "refractory" cement which is rated to 2000 degrees to handle the heat. Regular Portland will crack apart and even sometimes explode.
If I have an air gap and fire rated cement board under a 200lb wood stove that I bolt tight to the floor I'm thinking the board would crack? I will only do air gaps on the walls. The floor is the spot in qiestion. Can I bolt the wood stove to the floor without that stuff cracking out? I will have 2ft by 2.5 in angle iron that it sits on. Will that displace the weight enough to avoid wearing that fire rated cement board?
Fire rated cement board should be fine as long as the weight of the legs doesn't punch through from bouncing around. Since most wood stoves have a fairly small footprint, placing or even welding pads under the bottoms of the feet to spread out the load might be a good idea. Just a thought.
Yep, cement board should be fine as long as you distribute the weight enough. Luckily my stove has a pedestal under it so it will get bolted straight through our granite slab hearthstone and floor without worries about weight distribution... I'm installing it this week so I'll try to get some pics of the hearth/heat-shield/flue and all that good stuff.