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Using Tarps In Modern Earth Home Construction

by Bruce Lawson

There are many advantages to earth homes, including the fact that they are eco-friendly, inexpensive, and highly customizable. Most techniques rely on soil found at the construction site, supplemented with purchased sand, clay, or straw, and require very few tools. With a few buckets, a solid tamping bar, a level and plenty of personal labor you can construct a small cottage during a single summer.

Of course, you can purchase other equipment to make your work easier. One of the critical pieces of equipment that you should not overlook is a good vinyl tarp, like one from Billboard Tarps

Mixing Earth 

Whether you choose to build with rammed earth, cob, or earth bags, the most important part of your construction will be getting the correct mixture of sand, clay, and straw to make your building last. This is especially important when building with cob, which does not have plastic bags or wooden frames supporting its shape while it cures. 

The cob mixture is generally equal parts sand and clay, which is mixed together by stomping on it until it is the consistency of cookie dough. This is where a couple good tarps come into play. You should lay a tarp on the ground and the put your sand and clay on top of it. Pulling on the corners of the tarp while you stomp with your feet keeps the mixture contained and helps you turn it. A 5'x7' tarp generally works for an individual mixing, but you may want to get a larger tarp if you have a two person team mixing. 

Once your sand and clay is mixed, you continue stomping while adding straw until you get a consistency that sticks together. If you will not use the cob immediately, it is important to cover it with a second tarp to keep it from gathering moisture overnight. 

While rammed earth and earth bags are more forgiving when it comes to mixing the right ratios, they both still benefit from the same mixing technique, as it allows you to mix large batches and use your legs instead of your arms. 

Protecting Your Walls As You Build 

Many people choose to build their foundation and roof before they start constructing their earth walls. This provides protection from the elements for the workers and the walls. However, it also shades the walls from the sun, increasing their curing time. You may want to consider building your walls before you build your roof. You simply need to cover the walls with tarps, either tied to rebar or held down with large rocks, every night. During the day, take off all of the tarps to allow your walls to breathe and get hardened by the sun. 

For this purpose, you will need long, thin tarps. 12'x20' is a good size to look for, but custom made tarps with a longer length are easier to work with. 

Tarp Uses After Construction 

After you are done building your home, there are several things you can do with your building tarps. You can save them to use for water catchment in your garden, or you can use them for camping. If you do not think you will use the tarps in the future, they also make a great waterproofing layer for earth berms. 

Creating a berm against your home saves you from having to put finishing materials over your earth walls and provides extra thermal mass to keep your home a consistent temperature. To build a berm, you simply push earth against the side of your house.

However, there needs to be a waterproof layer between your walls and the earth to prevent condensation and mildew from entering your house. Simply take the tarps you used to cover your construction site and line the side of your home that you want to create a berm on. Then, fill the area with a layer of gravel and a thick layer of lightly tamped top soil.

Whichever method of earth building you choose, your ability to control moisture levels throughout the entire process will be critical to your success. You should invest in a few high quality vinyl tarps for the best results.