Designing Post and Beam

One of the most common strategies for getting a building permit in areas where earthen architecture is unfamiliar, or officials are heavily biased against it (usually from ignorance of the medium), is to incorporate a post and beam framework as the load-bearing structure, delegating the bag work as infill. This is contrary, of course, to all one's efforts directed at minimizing the use of lumber and energy intensive materials like cement and steel. At least it may help you get a house built, while introducing an alternative building method like earthbags.

One way to limit the use of lumber is by using small dimensional posts, like four-inch by four-inch (10 cm by 10 cm), set at the furthest distance allow-

5.14: Two continuous locking rows of bags or tubes above the finished window or door openings.

5.16: The second row of bags lock down the Velcro plates and wrap around the posts.

able;about eight feet (2.4 m) apart. Here is an example of one system for installing a post directly on top of an earthbag stem wall for such reasons as building in a glass wall or infilling with strawbales (Fig. 5.15 & 5.16). Most post and beam structures require an engineer's stamp of approval and naturally they will want to beef up the top plate (bond beam) to cover their own butt. The bag work easily swallows up the posts by wrapping around them. The posts, set eight feet (2.4 m) apart, allow plenty of space to build window and door openings around forms, or add more posts to use as built-in window and door forms.

One advantage of using posts as the load bearing structure is that supporting the posts on concrete piers (instead of a continuous concrete foundation) permits you to do the bag work on top of a rubble-trench-and-stabilized or stone, stem wall foundation. If your project is not subject to the scrutiny of building code regulations, consider yourself luckier than if you had won the lottery. All those damn posts can sorely interrupt the flow of the wall system by breaking up corners with posts, etc. They also increase the cost per square foot and slow down the building process.

Perhaps one of the simplest and strongest post and beam configurations is a circle with 4-inch by 4-inch (10 cm by 10 cm) posts set at eight-foot (2.4 m) intervals on piers. Infill between the posts with earth-bags set on a rubble trench foundation. Use forms to build arch openings. When the bag work is level with the height of the posts, build a faceted wood beam or top plate, or pour a concrete bond beam. Roof the structure according to taste. This recipe will at least help to lessen the use of wood, cement, and steel, while still meeting most building code requirements. It all depends on how much you are willing to compromise, depending on your personal point of view. Here are examples of what we are talking about when we speak of compromise.

Alison Kennedy wanted to build her house using earthbags, here in Moab, Utah. Although the building codes in Utah at that time allowed for load bearing adobe walls, the adobes had to be stabilized. Rather than adding the extra work involved in mixing cement into all the dirt, as well as killing the natural character of a living soil, she opted to install posts and beams in the form of precast concrete blocks (Fig. 5.17).

5.17: Alison Kennedy's code-approved earthbag home with concrete-block posts and beams.

Sarah Martin's addition onto the back of the Comb Ridge Trading Post in Bluff, Utah, made use of an existing foundation, set with posts, that had been installed by the previous owner. She and a crew of friends infilled all the bag work in two weekend parties that included food, libations, and copious amounts of laughter and merriment. The barbed wire was installed in a figure-eight pattern, weaving its way inside and outside each pole throughout the entire wall system (Fig. 5.18).

5.18: Because the posts were fairly narrow, the bags swallowed them up as they conformed around them.

Keep in mind that many of these design considerations are in direct response to the limitations imposed by existing building codes. Don't think of these restrictions as impedance to your desires to build with more resource-friendly materials. Rather, think of them as opportunities for creative problem solving. If you choose to work within the system, compromises will likely have to be made, but your building department will be making concessions, too. And you are providing them with the opportunity to learn new techniques and, just possibly, open their minds to something that works outside the status quo. Creative potential is contagious.


Was this article helpful?

+1 0
Greener Homes for You

Greener Homes for You

Get All The Support And Guidance You Need To Be A Success At Living Green. This Book Is One Of The Most Valuable Resources In The World When It Comes To Great Tips on Buying, Designing and Building an Eco-friendly Home.

Get My Free Ebook

Post a comment