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Hydronic radiant floor DIY using cement boards.
We are planing to install hydronic radiant in our house that has concrete slab. The house was built in 50 and it original had radiant floor, however it is impossible to recover that system. We want to use 1/2 PEX tubing but we are very limited with height. We can't go higher than 3/4 of an inch. It would be convenient (and expensive) to use wooden panels designed for that. However, as far as I know the thinnest for 1/2" tubing is 1". Other thing is that it won't transfer the heat in between the tubing and if we use heat transfer plates it would add additional cost. My idea is to either have tubing mounted to concrete slab and then pouring it over with self leveling concrete and here is my first question: How thin it can be? Would 3/4" would be enough to prevent significant cracking? Other option is using cement boards cutting them to fit in between the tubing and gluing them with contractor adhesive to our slab - similarly to the attached photo where they use playwood. Would it work and last? Did anyone tried that? The reason why I prefer to use cement boards instead of plywood is that it will transfer more heat. The last question is what can I use as an insulation while considering very thin self leveling cement or cement boards. Any other ideas how to do it are welcome. Just keep in mind that we can make it only 3/4" thick, we are on a tight budget, and we are determined to do it before we move in (because I know it won't be possible while living in the house). The house is about 1600 square feet on concrete slab.