Re: SLC & Radiant Heat Flooring by Todd Groettum Ok, so my husband and I are DIY wannabes...that is we have a list a mile long of things we plan to do ourselves on our house, but have yet to really attack any of the big ones. At the top of the list is our kitchen floor. Todd - let me just say that after weeks of research this article is the first I've seen to touch on all the aspects of what we need all in one place, so thank you for that! We currently have a kitchen/small dining space that is currently ceramic tile/rug respectively. We found an amazing deal on some gorgeous marble tiles about 8 months ago and bought them for the whole space. We plan to rip up the existing tile and rug in this area (and disgusting linoleum we found underneath it while moving an island) all the way down to the plywood subfloor. The current tile is clearly not flat or level, which I know would be a big problem for marble. In all my reading, this is our basic plan: 1. make sure the joists aren't too far apart for structural soundness 2. lay down cement board (would there ever be any reason for a new layer of ply first?) 3. install radiant heat mats (we're looking at suntouch from HD) 4. Use SLC over the mats to be sure the marble tile gets laid completely flat and level 5. Install tile with white thinset and 1/8" joints 6. seal tile to avoid scratching and grout with unsanded grout So as you can imagine, your article is EXACTLY what I need to be sure we don't screw this one up. I only have a few questions after reading this article. 1. Do we actually need the cement board if we're going to use SLC over the mats? 2. If so, would we need to fill and sand the seams/screws before priming? 3. Forgive my ignorance, but this is the first I've read about Dam Blocks. Does this mean I will have a 1" gap between the SLC and doorways, and where it will meet the rug in the livingroom? And are these used in place of the foam strip for expansion or in addition to? I guess this step went right over my head.