Frequently asked questions
Why shouldn't my next house be a wood frame house like all the others?
Even though wood as a building material is plentiful, so is soil. Earthen walls will never burn (there's even proof thanks to a two-hour code-approved, regulated fire test) or rot. Most of the oldest surviving residential structures in the world are earthen structures. Earthen structures resist high storm wind conditions. Earthen walls do not have cavities like conventional light frame walls and therefore will not harbor pests or allow mold growth. Earthen walls are also tested against ballistics and proven to be bullet proof.
Will just any soil work?
No. For starters, when most people think of soil, they think of the topsoil around their houses that contains a lot of biological stuff like roots, mulch, bugs, and high organic content. These things are not desirable to use for earthen construction. It's best to use the soils below the organic layer which may be three or more feet below the surface depending on your particular soil's composition.
Does that mean I have to have soil delivered to the building site?
It might mean soil would have to be delivered. If the soil on your property has a high clay content, you might just have sand delivered to mix with the soil. The critical issue is that you should have your soil mix tested after blending to see if the blend will produce a compressed block or rammed earth wall that will structurally perform as expected or better. Once earthen construction becomes more common, sources of acceptable soils will be better known. Also, there may be sources to purchase blocks at block yards that are stacked on palettes and ready to go. In the meantime, all types of appropriate soils and blends can be found at local quarries and fill yards.
Once I get below the organic layer, will I be able to use the deeper soil near my house?
Maybe. Soils that are ideal to use in earthen construction need to have a combination of clay and sand. A certain amount of silt could be appropriate too. Too much clay, sand, or larger particles in the mix can result in problems in the finished structure. The appropriate proportion of soil constituents, clay, sand, silt, and gravel will vary with the type of earthen construction.
What happens when it rains? Won't the walls erode away?
If individual compressed earth blocks are left outdoors exposed to the weather, yes, they will eventually erode. But if earthen construction walls are covered with compatible and properly applied plaster, erosion will not occur. In some cases, a decision might be made to add a small percentage of lime or Portland cement to add another factor of weather resistance. Compressed earth blocks that are augmented in this way are called stabilized blocks. However, this description does not mean that blocks without lime or cement are unstable. Either category of block can be used.
Your architect or builder can help you to determine whether or not to use stabilization in your particular case.
Is it true that it costs less to cool an earthen structure in the summer?
Preliminary studies in South Texas indicated that interior spaces of earthen structures were found to be cooler in the afternoon than they were in the morning. It's too early to definitively determine the science behind the effect or what conditions and design elements might maximize natural cooling, so ECI is planning to engage in further research to explore the phenomena. If the results reinforce current observations, air conditioning systems can be downsized thereby saving the cost of equipment and electric bills.
What about heating in the winter?
An interior heat source will be needed to provide comfortable interior temperatures, but earthen walls are excellent in absorbing radiant energy to help maintain warmth. Again, research in tracking temperature and humidity year round will eventually be used to determine adjustments in mechanical equipment design.
Is earthen construction a good environmental choice?
Studies are now being done to show that the amount of embodied energy of an earthen residential structure is significantly less than conventionally built residential structures. Embodied energy describes the energy required in extracting natural resources, processing materials, delivery of materials, assembling materials, and disposal (or recycling or repurposing) materials at the end of use. This means that less carbon and greenhouse gases are emitted into the atmosphere. This is another area of research that ECI intends to pursue. Add to the embodied energy the energy required to air condition or heat the structure, and factor in the life expectancy of the structure, and earthen construction is likely to perform better than conventional construction in the long run. Due to the complexity of light frame cavity wall construction, conventional construction is made from many more materials than the typical one or two earthen wall components. Many of the materials used in conventional construction are toxic or otherwise hazardous either during application, use, or during a fire or exposure to dampness.
If earthen homes are such an improvement, why aren't builders offering them now?
Homebuilders operate in a highly competitive market where even relatively small decisions in what builders provide can make the difference on how long new homes stay on the market. Builders are concentrating on offering a low cost per square foot home. Earthen construction is currently more expensive to build. Due to the large number of variables, and not many earthen homes available now to compare costs, it's currently impossible to give a certain percentage for how much more expensive earthen construction is compared to light frame construction. Foundations alone are more expensive due to the ability of the foundation to support a much heavier home.
I hear a lot of talk about resiliency. Does earthen construction address durability and safety?
A building's resiliency is determined by the durability of the structure and ability to withstand extreme and more frequent weather conditions. A well designed and well built earthen structure, although not totally indestructible, can survive severe events better than conventional construction. Keep in mind, however, that measures must be taken if the earthen structure is planned on being built in an earthquake zone such as the Pacific coast.
Besides stabilization, are there other measures that can be used to encourage durability?
Yes. The desert regions where most American residential earthen construction can be found are quite dry and have very little rainfall and humidity. Earthen construction is not as common in the rest of the country, but examples do exist, not to mention world-wide use in all kinds of climate conditions. Never build on a site prone to flooding of course, but an easy way to ensure durability and low maintenance is with a good hat and boots. The hat refers to wide roof overhangs. The boots refer to protecting the bottom of the earthen wall. It must sit on a non-absorbent stem wall base so that moisture cannot be wicked up from the ground or be splashed by water coming off of the roof. Sloping the finished grade away from the exterior walls also protects the earthen walls.
If they're more expensive to build, won't I save money by buying a conventionally-built home?
Yes, initially. During the life of the home, however, maintenance and utility costs are likely to be less for an earthen construction home compared to a conventionally built home built to the same level of care and attention to good practice detail. Also, keep in mind that the typical home or commercial building has an estimated life span of 50 years. While earthen construction buildings, when properly constructed and maintained may last over 100 to several hundred years. As a result, earthen structures are much less expensive over the life of the building.
What if I don't want my house to look like a flat-roof desert house like I see in the movies?
You don't have to. Not all earthen structures have to look like desert homes or the Santa Fe style. Many of today's residential styles were actually based on historical residential styles of northern and central Europe that were made with earthen construction. Even the mission style is based on thousand-year-old or more earthen and stone buildings from the Mediterranean. Because of this, earthen construction can easily be re-adapted to their original historical roots. Earthen structures are uniquely suited for incorporating vaults and dome roofs.
If I decide to have an earthen home built, can I get financing and a building permit?
It depends on where you wish to build. It is already possible to obtain financing, but it may be a challenge to find. As more examples are built, more lenders will be comfortable with the value of earthen construction. As for building permits, check with your city and county building officials. More permits are being issued where they are required likely due in part to the current residential building codes defining compressed earth block and rammed earth as categories of "mass walls" (2015 International Residential Code N1102.2.5).
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