Replacing and Insulating an Earthen Floor: Part 1

by ziggy on August 30, 2011 -- 2 comments -- Follow


Removing the original earthen floor

The project of replacing the earthen floor is still continuing, as we wait for the base layer of earthen floor to dry before we proceed with applying a finish layer. This gives me a chance to describe what we have done so far to tear up the floor and insulate a brand new earthen floor.


Exposed gravel underneath the original floor

Removing the earthen floor

First and foremost was demolishing the existing floor with a pickaxe, which you can watch as a video here. Easy enough: slam a pickaxe enough times into the floor to break up the floor, and then carry out all of the material in buckets. We got down to gravel and then raked the gravel to be level, as we had disrupted it a bit with all of the shoveling and pickaxing. Getting at the edges around the foundation was the most difficult.


Our bed frame hanging from the roof rafters (!)

Installing a vapor barrier under the earthen floor

Since the bed frame could not be dismantled (the screws were impossible to remove from the osage corner posts!), we decided to hang it from the roof rafters. A crazy notion, I first thought, but probably the wisest choice. It was pretty annoying to work around at times, but nowhere near as annoying as having to destroy the bed frame and make a new one!


Smoothed, level sand bed to protect the liner

Anyway, once the bed was out of the way, we dumped a good 1″ of fresh sand on top of the raked gravel to provide a smooth buffer between the gravel and the plastic liner that would come next.

Then we rolled out a layer of 6 mil poly liner, and with utility knives, carefully cut the sheet to the shape of the house, leaving a good 6-10″ extra on all sides to flare up the foundation.


Cutting the “scribed” rigid foam board insulation

Insulating the earthen floor with rigid foam

On top of the liner we laid down 1.5″ thick rigid foam insulation. (Read my thoughts about the difficult decision to use pink foam insulation in our earthen floor.) It was no small trick to try to fit square 4’x8′ foam boards into an irregularly shaped house. We ended up discovering that “scribing” the foam was the most effective trick to get a relatively clean fit against the foundation.

That involved using a straight edge (a ruler with holes in it was ideal) with a pen, and “riding” the edge of the foundation with the straight edge perpendicular to it, tracing the outline of the foundation directly onto the foam board. In the photo above, you can see Jacob then cutting along our scribe line with a utility knife. Any gaps we stuffed with smaller off-cut pieces of foam.


Earthen floor base layer installation in the works

Applying the base layer of earthen floor

Finally, we started applying the base layer of earthen floor, a very simple mix of 1:1 clay and sand. No fiber this time, just straight up clay and sand, heavy on the clay to make it smooth and easy to work with. (Plus, clay is free, and sand is not.)  I expected the floor would crack, and it has, but this is no problem since the finish floor will “key” into the cracks. The base layer is approximately 1.5-2″ thick.

It was dumped by the bucket, flattened out by hand, and then troweled smooth and level with a pool trowel. I must say, troweling floors is pretty fun.

That’s where we’re at right now. The floor has been drying for two weeks and is nearly ready for the finish coat. Our ultimate plan is to actually tile the floor, so there’s a whole new adventure ahead once that finish layer is nearly dry…

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  • Hello! We are building a strawbale timber frame house, and have put in a section of earthen flooring. I am looking around for methods of filling the thin cracks that appeared. I enjoyed reading about your progress, and hope that the new floor is working out. We also had to rip up our first attempt because it didn’t bond well to the sub layer. We put a layer of burlap between the layers and didn’t wet it enough. Oh well. At least the burlap made it easy to pull up. I am also keeping a blog about our progress, amongst other aspects of life. Thanks!

  • The points you have given here are incredibly precious. It turned out such a pleasurable surprise to see that waiting for me as i woke up today. They are always to the point as well as simple to understand. Thank you for the innovative ideas you have shared above.

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