by Dr. Owen Geiger
To illustrate just how easy earthbag building can be, this article shows each main step of construction for building vertical earthbag walls. Earthbag building has enormous potential, especially for affordable housing, but it hasn't caught on yet in a big way. Hopefully this article will help bridge the gap.
The building techniques shown here were used on a recent housing project in Cambodia and proved to be significantly faster than methods shown in books and websites. Some people may think earthbag building is too slow or difficult, but it doesn't have to be. Follow these steps and you and a half-dozen friends can build the walls of a 625 square foot (8m 2 ) house in about 5 days. (Even less for strong workers.)
The following instructions assume you have cleared and leveled the site, removed topsoil, positioned fill soil around the building site to minimize work, dug a trench to stable subsoil, and added corner guides and stringlines.
1. Tools and materials: woven polypropylene bags (about 18” x 30”), tamper, shovel, bucket, sheetmetal slider (about 14” x 24”), 4-point barbed wire, plain wire, wire cutters, knife, hammer, tape measure, level.
2. Fill the bags: use small buckets to measure the fill material (use gravel on lower courses); fill approximately 80% full. This technique ensures each bag is the same size, which helps keep each course level. (Optional bag stand not shown.)
3. Sew the bags closed: fold the bag end over; use 20 gauge wire with one end cut at a sharp angle and make about 5 or 6 stitches. This technique facilitates handling, prevents spills, and allows bags to be filled completely.
4. Lower courses: place gravel-filled bags (double bagged) working from the corners and openings to the center; align to stringline; tamp the bags solid after the course is complete, working from the center of the bags outward.
5. Add barbed wire: use one or two strands of 4-point barbed wire in-between each course of bags; bricks or stones hold it in place.
6. Use a sheetmetal slider to place additional courses: after the bag is aligned, hold the end of the bag (it helps to lift it slightly) and jerk the slider out.
7. Repeat the process using earth-filled bags, but with a few minor changes: tamp the contents slightly after each bucket load is added; lay full bags in a row flat on the ground alongside the wall; stomp each bag a few times with your foot to flatten it somewhat; swing the bag into place in one motion, with the sewn end jammed against the previous bag; maintain a running bond as in masonry.
8. Make custom-sized bags to fill odd-sized spaces: measure the opening; fill the bag to the approximate level; cut off excess bag material and sew closed (or fold the end over), and place the bag in the wall.
Notes for ‘speed builders'
Here's a recap of important points, along with a few other comments to maximize production.
- First of all, get ‘clean' (mostly free of rocks, roots, and large clay chunks) sandy-clay soil delivered to the site and dumped in piles around the building.
- To minimize handling, fill the bags right next to where they will go in the wall.
- Swing bags into place in one motion.
- Gravel could be shoveled directly from the truck into bags. Also consider a rubble trench foundation.
- Work in teams -- say, two teams for a small house -- and try a little friendly competition.
- Bag size is important. A slightly larger bag may be too heavy. Experiment.
- Refine your technique for making custom-sized bags – they tend to be a real time killer. One idea is to hold a partially filled bag next to where it will go and eyeball how much soil to use. Add more than you think because it will compress quite a bit.
- Let go of perfectionism. There's a middle ground between high-precision work, such as masonry, and careless work. Use reasonable care and no one will notice minor imperfections after the plaster goes on. And, if need be, it's relatively easy to tweak the wall with a tamper before plastering.
- Also, there's no need to tamp the bags excessively, just tamp until they're solid. 30 seconds should be plenty, maybe go a minute if you're slow and tired.
- Although much slower, use the ‘can method' of filling bags one can at a time high on the wall if the going gets too tough.
More information and more photos will be added soon to my Publications page: www.grisb.org/publications/index.htm
Owen Geiger, Ph.D. is a TLS Correspondent and the director of the Geiger Research Institute of Sustainable Building. www.grisb.org
Photo credit: Meemee Kanyarath