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Build a Bamboo and Earth House

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Berkeley based Natural Builders worked with a local team to build this house in Costa Rica using bamboo joinery and the infill between the posts using the earth and bamboo “wattle & daub” technique.

The wattle and daub technique is an ancient time tested method of building. A basket-like wall (wattle) is combined with an earthen layer (daub) that is plastered into and around the wattle. This wattle and daub area is bounded by larger wooden posts, in this case using 6″ bamboo poles.

Frame your building using bamboo beams 6 inches thick or greater. Using bamboo is the most sustainable way of building with this technique as it is the fastest growing wood we have.

Harvest materials

1. Step 1

   Gather thinner bamboo sticks about a 1/4″ diameter for the wattle (woven bamboo) that will go into the wall. Cut these bamboo sticks so that they are as long and as straight as possible. They need to be flexible enough to weave without breaking and thick enough to hold up the daub.

2. Step 2

   Gather thicker (about 2″) bamboo sticks for the daub supports. These do not need to be as flexible, as they will serve as structural support for the wall. Cut these thicker sticks 6 inches longer than the space you are going to put them into between the timber walls.

   Insert 2-Inch Sticks

3. Step 1

   Insert the 2″ bamboo sticks into the header holes all the way up, then drop the sticks into the bottom of the footer holes.

4. Step 2

   If these are too large or irregularly shaped, whittle the tip to a smaller diameter. Cut into the bark all the way around to the depth that you desire and tilt your knife to split the wood off towards the end.

5. Step 3

   Cut a small wedge or “shim” to hammer between the 2″ sticks and the holes they are in (top and bottom) so that they are in tightly.

   Weave Smaller Sticks

6. Step 1

   Now weave the 1/4″ sticks in and out of the ones that you just set. Alternate the side that the weaving starts on, as you weave one layer at a time, stacking the layers until you gradually reach the top of the wall. After each layer is placed, spank the top of the weaving with a mallet. This helps to pack the wattle down, making a tight basket.

7. Step 2

   Deal with the ends of the weaving by trimming and inserting the weaving into the dado you cut. The trimming can be done with limb clippers or the ends can simply fold over and be woven into the surrounding wattle, which is then slipped into the dado.

8. Step 3

   Test the weaving to make sure that it is strong by carefully pressing with your open palm on the weaving. The weaving should (ideally) hold when you press on it but remember that the daub will add reinforcement.

   Adding Daub and Plaster

9. Step 1

   Make daub from clay and sand (70/30 mixture ratio). Mix the clay and sand with an equal amount (by weight) of straw. Sometimes animal blood or manure is added to the mixture. Mix it together thoroughly by walking around in a pile of it on a hard surface. Press the mixture into the weave of the wattle so that the daub oozes into the nooks and crannies for a good grip on the weaving. Pack the entire wall like this so that the wall starts to take shape.

10. Step 2

    As the wall starts to approach 4-inches. make sure that the wall is flat and even. You will have to do this in 1/2-inch layers, allowing the wall to partially dry between applications, so that the wall is strong enough to stand. Make sure that the wall dries completely before plastering (2 to 3 weeks or more if the weather/climate is moist).

11. Step 3

    When the wall is thick enough, add a layer of plaster on top of the wall to smooth it out. The plaster can be waterproofed with the addition of various ingredients to the plaster to prevent water breaking down the wall. The wattle and daub part of the construction is done.

Natural buildings are healthier for the people who live in them and healthier for the planet.

From The Natural Builders