Earthen building and the code

We get many questions about how earthen construction works in conjunction with the building code. Here are some of our insights:

1. Building regulation is necessary.

Buildings influence more than just your own life. They should be built to high standards of health and safety and consider the surrounding area and resource management. If your house catches on fire, your neighbors house might too, and so may the forest around you. If you build a larger house than you need, you are stealing resources from the earth and from our grandchildren.

Unfortunately, building codes have morphed into a narrow set of safety regulations, mostly geared toward using commercial building products and meeting engineering standards. In some ways this has been a success story, in particular for the finances of the building industry, the banks, the tax collectors, realtors, architects, contractors and housing developers. Additionally, the larger buildings in our ever-growing cities require good oversight to ensure they are safe. High-rises, football stadiums and apartment complexes should have high engineering standards!

For those of us who want to choose a more simple life, building codes seem like an obstacle. The codes seem to push the building industry toward structures that are more complex, more expensive, more toxic, and more square feet. It would be nice if there was a separate standard for large, complex, energy intensive structures, and another one for people who want to build modestly and responsibly: a “People’s building code”. Some counties in California already have such a thing, sometimes referred to as the “owner-builder code”. In the absence of such a code, there are still ways to practice earthen building methods within existing regulatory framework.

2. Earthen buildings are not illegal.

It is important to understand that the code does not “outlaw” building with earth. On the contrary, many codes contain language that encourages building officials to experiment with new, environmentally friendly, ways of building. However, because of liability concerns and lack of understanding, seldom will a building department approve things without the approval of a structural engineer, which can be a long and costly process.

Most building codes are local. Counties usually start with adopting the national code and then can make changes as they see fit. For example, insulation codes are different in Buffalo, NY than they are in San Diego, CA.

The final authority usually lies with the inspector coming to the building site. This can be good and bad. You may have built according to a set of approved plans and still be rejected by the inspector; conversely, you may do things that seem reasonable but would never get approved by the plan reviewers, yet a nice inspector will approve it on the site.

All these things suggest that building codes may not be as rigid as they appear. Taking on the attitude that the codes and code officials are there to help, rather than hinder, will help you achieve more of your goals.

3. You can get most of what you want!

Many earthen building methods don’t even require the approval of an inspector to use. Earthen plasters can be applied on the inside and outside of most buildings, earthen floors are seldom a problem. Non-load bearing interior walls can be made of such things as cob (make sure the floor is strong enough) or light-straw-clay. Outdoor rooms and patios can be shaped by cob, some form of earthen brick or earth bag walls.When approaching it from this angle, it opens new and creative ways of thinking, by not defining a house solely by what holds up its roofs, but rather by the sum of all the materials inside and out. This change of perspective can help us become aware of the fact that it’s not just the code that is in the way: it’s also the way we define houses. For example, I built a house where 2×4’s hold up the roof, straw bales provide the insulation in the walls, cotton provides the insulation in the ceiling, earthen plasters and floors cover the inside and interior cob “pony” walls shape interior spaces. Both inside and out, the house feels overwhelmingly like a “house of earth” and was easily accepted by the code officials. No one calls my house a 2 x 4 house, or a cotton house, even though it is just that, as much as it would be a cob or a straw bale house.

In summary, the structural (load bearing) part of a house is only a small part of what creates the overall spirit of the house. We believe that you can get a better house by not simply focusing on what materials hold up the roof.

4. Structure

It is still valuable to take a closer look at the structural component of a house and how it applies to earthen construction. For all municipalities, except for the few with an owner-builder codes, the supporting structure of a house (the part that holds up the roof and prevents it from blowing away) needs to be engineered. The strength of materials made from local ingredients like earth and straw are difficult, if not impossible, for an engineer to calculate. It can theoretically be done, but could require testing each individual batch of cob, and it would be very expensive.

Simple wood or metal framed walls can be easily designed to please the most conservative engineer, and at very little cost (the building industry has done all the work for you: the load-bearing capabilities of lumber and steel are very well known). This is especially true if you keep the shape of your building simple (a very good idea!). Once the “skeleton” is approved, you can fill it in with your choice of building materials. That is more or less how most straw bale houses and light-straw-clay houses are built: the support members are not actually the straw bales, but rather a stud-or timber frame structure. (Load-bearing straw bale buildings are possible, but that is a different article…!).

5. Insulation

Most counties have strict rules with regards to the amount insulation required in the walls and ceilings. An earthen wall would have to be over 2 feet thick in order to comply with many of these standards. While a 2′ earthen wall would be fine (and even architecturally appealing), it’s a lot of work and not necessary. Through a simple calculation, you can compensate for lack of insulation in the walls by adding more insulation in the ceiling. Since warm air rises and mostly wants to get out through the ceiling, putting extra insulation in the ceiling makes a lot of sense. The building code actually provides a calculation you can do yourself, which can then convince building officials to let you have a little less insulation in the walls.

Insulation value is expressed in R-value. The greater the R-value of a material, the more slowly heat (or cold) will travel through that material. In areas that have cold winters, or very hot summers, a minimum R-value of 19 in the walls and 38 in the ceiling is typically required. A 18 inch earthen wall has an R-value of about 9, not enough for the code.

Here is how the calculation works:

Let’s say that the total square footage of your walls (minus doors and windows) equals 1000. If you multiply that by 19, that would give you the number of “insulation points” the code requires you to have, in our example that would be 19,000.

However, you are planning to build with earth and only will have a wall with an R-value of 10. This would give you 10,000 point. You are thus 9,000 points short. Now, let’s say your ceiling is 700 square feet. The required R-value is 38, which would give you 38×700=26,600 points. If you were to increase your ceiling insulation by a little more than 1/3, you would gain the 9,000 points you are lacking in your walls.

This would be relatively easy to do and would also make a lot of sense in terms of creating a comfortable building envelope. You would actually end up up with a better insulated building because increased ceiling insulation is more effective than increased wall insulation. (Heat rises, remember?)

6. Misunderstandings about the “200 square foot” rule

Many counties allow people to build small structures without needing building permit. Sometimes the maximum size is 200 square feet, sometimes less. Sometimes they measure the inside floor space, sometimes the whole footprint of the building. There are also often height restrictions. Check with your local department to find out what the specifics of this rule are.

However, please remember: These small structures are meant as auxiliary buildings to existing, permitted structures. If you put plumbing and electric in it, you still need to get separate plumbing and electrical permits for those features. According to the building department, these are under no circumstances considered “livable structures;” you can not legally sleep or live in them. If you spend the night in one you are by law “camping” on your own land, which is often only allowed for a limited number of weeks per year. The “200 square foot rule” is meant for storage sheds, barns, etc, not for permanent living. But with a small water jug and sink, some LED lights and a camping stove, you can carve out a nice “cottage lifestyle” without causing too much suspicion. It is not practical for the building department to come and check to see how many nights you are camping in your small cottage. And if for some reason they do come out and order you to stop living there, as long as the building is under the maximum size for a non-permitted structure, they can’t make you take it down. Once the county officials have left, you can quietly move back in!