We're getting a new wood stove soon, we hope, and I'm tearing out the old hearth today. It takes up a lot of space, and it's off center. The former owners did this to accommodate a large couch. We don't need an air space behind and under the hearth (not a code requirement), and we also aren't required to install cement board on the back wall. But I do intend to use it in the construction. Any flex in the floor can crack tile, I know I can put the cement board directly on the wood floor and screw it into the joists. Our subfloor is a thick, jointed wood, no plywood. I'll probably need 3.5" screws. I have a trap door to the crawl space where I can measure this and make sure I've got it right. But how do I locate the joists? If I decide to build a platform out of 2x4s on edge (not laid flat), would I need to screw the platform to the wood floor? With long enough screws it could pass through to the jointed wood subfloor. I wouldn't know how to hit the joists. Is this necessary? Also, I've read that cement board can be brittle, so would it be best to first lay down some plywood on top of the frame? As for tile, porcelain is stronger and less likely to crack. But the current hearth has been there for 25 years and is tiled with faux bricks that are maybe 1/2" thick. No cracks anywhere. I like the idea of larger tiles on top of the platform and smaller ones to cover the sides of the platform and for the back wall. I just need to get an idea of how to build a strong platform, spacing between the boards, and how to ensure the tiles won't experience any movement, and then I need to chose the tile. I'd sure welcome some suggestions. I'm taking down the bookshelves and dismantling everything today. Once the hearth is done and we finally have some heat in the house, I'm going to build some floor to ceiling bookshelves on either side. It should be nice. Thank you.