Concrete hearth detail

After @yourconcretesource shared our concrete hearth building timelapse the other day, I realized that we never talked much about the finished product.

In looking for a hearth solution for the tiny house I wasn’t thrilled with the usual options. Tiling over cement board is time-consuming and just kind of annoying to get out all of the tools you need just to tile a two foot square surface. Also, in my experience you invariably end up chopping kindling on the tile which breaks the tiles over time.

With this in mind we decided to cast a reinforced solid concrete block. I used scrap wood for the 2” x 26 x 26 mold, smoothing the interior with epoxy, caulking the corners, and smearing on paste wax as a release agent. Better results could have been achieved with melamine but it just seemed indulgent to buy a new sheet of wood when I had scraps sitting around. We mixed up a fairly dry batch of high PSI concrete and pressed the rebar grid into it hoping that it would stay somewhere in the center of the mold. I used a sawzall without a blade in it to vibrate the air bubbles out which I thought was pretty clever, then screeded off the excess.

We sealed it with a random concrete sealer that I bought at the hardware store, which looked cool wet but dries the same color as it was. I didn’t want to put a heavy acrylic or epoxy coating on because I wasn’t sure what kind of chemicals it would off gas as it heated up. 26 x 26 ends up being a little bit too small and to do this again I would go 28 x 28 or even 30 x 30. Ideally a hearth should be much bigger, but the size of the space dictates some compromises.

The finished product turned out better than expected. It sits on the wheel well box in the back and on 2.5” square legs in the front giving firewood storage space underneath. It weighs about 100 pounds and gives a nice, simple, strong fireproof surface for the Dwarf 4K stove to sit on. It gradually gets warm and then gradually cools down over the course of the night. Also, the rounded edge is perfect to curl our toes onto while chillin in the hanging chairs.

– Brian

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