(Very Large) Earthen Floor Installation

by ziggy on August 27, 2017 -- 1 comment -- Follow

This week, I traveled to eastern Pennsylvania to work with Gabe Franklin of The Art of Plaster to install a large earthen floor in a straw bale home. We’ve been in talks about collaborating and this project was the perfect opportunity to sling mud together. And here I thought the 900 sq. ft. floor of this spring was big — this floor comes in at 1500 sq. ft. Earthen floors represent a lot of hard labor, so  the good company and our mutual love of clay carried us through to the end.

Read ahead for some more photos of the process!

Large Earthen Floor Installation

Truly the most difficult thing about earthen floors is the very physical nature of the work. It’s all hands and knees for hours at a time. You’d think that fighting gravity when you’re plastering walls should be more difficult — not so at all. At least you’re standing when plastering.

Earthen floor - wood float

Gabe floats out some floor with a wood float

We used site clay soil, cement sand, and chopped straw for the finish layer of earthen floor. There’s a sweet spot when it comes to thickness and moisture content — if the mix is too dry, it will be difficult to push and pull. Too wet, and it will develop a subtle wave when you float the material. Also, the risk of cracking increases with a wetter mix.

Anything over 3/4″ thickness is a bit daunting to install. Each small increase in material is just that much more material to move around. It’s amazing what difference 1/4″ in thickness will make. Honestly, 1/2″ is a really nice thickness to work with — you can get away with a little bit of extra water in the mix and have an easier go of floating things out.

Earthen floor closeup

Butta, baby

The most useful tools seem to be a couple of wood floats in varying sizes, a magnesium float, and a finishing trowel, either carbon or stainless steel. Tiny wood floats or steel trowels are great for compressing finicky areas of floor, but the wood floats see the most work typically.

earthen floor trowels

Earthen floor tool lineup: wood floats, magnesium floats, steel trowels, etc.

Here’s a Japanese stainless steel trowel designed specifically for compressing floors. It works really well with the sweet spine and handle design — you can apply a ton of pressure without deflection.

Earthen floor compression trowel

Stainless steel compression trowel for final burnishing

I calculated that we used about 94 cubic feet of material in total. That’s about 140+ buckets of mud… no slouch. Amazingly, we finished the overwhelming majority of the floor area in 5 work days between one person mixing and two people laying material down. Whoa..

Earthen floor - great room

Bucket after bucket after bucket…

Most surprisingly was just how fast the floor was setting up and drying. Since there was no possible way to finish this floor area in one go, we had to be careful about protecting seams overnight. The best luck we had was soaking burlap in water, and laying that over our work with another layer of plastic for the night. Because stuff was drying so quickly, it was difficult to blend the next day.

Often we were getting back on the floor within hours to compress it down. You can do this by laying pieces of rigid foam and walking carefully across the floor area. The foam disperses your weight and leaves only a subtle indentation that can be easily troweled out.

As the floor dries, the color lightens significantly. Once it’s 100% dry (and only 100% dry), it can be oiled.

Earthen floor drying time

The color of the earthen floor lightens as it dries

Success!

Earthen floor finale

The end!

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  • Ben Zolno

    wonderful work! Thank you!

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