You may think that you can huff and puff and blow this house down, but unless your name is Superman, think again. The Straw Bale hasn’t been around nearly as long as cob or rammed earth, but it has proven to be a very substantial building material starting in the late 1800’s when new settlers in timber-poor areas of the American plains scratched their head, looked around and said, “So, what DO we have to build with?”
There are two prevalent means of using straw bale as building stuff and they are load bearing walls or infill. Load bearing is just that…bales are stacked one upon the other, holding up the second floor, the roof and a snow load without any effort at all. Compression tests conducted by engineers (as described in ‘Buildings of Earth and Straw’ by Bruce King) show that bale walls could support a load of 10,000 pounds per square foot compared to the standard 2×4 wood framing which can only handle 1,500 lbs per sq. foot. Along with this information I find it very reassuring that if you spike rebar vertically from the foundation all the way to the top unifying plate thus clamping everything tightly together, a straw bale house can resist 100 mile per hour winds. In other words, huff and puff on Mr. Wolf cause this house ain’t going any where.
The other method is an infill wall whereby post and beam framing acts like a skeleton supporting the weight of the house. The bales then are stacked between the beams acting as insulation. In both cases you don’t want to skimp on the foundation. Great care must be given to purchase your bales dry and KEEP them dry as moisture and mold are a concern if they get wet. In an effort to keep them dry suitable overhangs must be present to protect the walls from driving rains, plus toeing up the foundation helps so that the first course of bales is laid minimum 6-8 inches above the earth (or grade). Other preventative measures are moisture proofing the surface of the foundation with something non toxic like the organic sealer DynoSeal since that is where the bales will be touching during the lay of the first course, and applying a layer of waterproofing in between. Last but not least allowing the walls to ‘breath’ so moisture can escape is another consideration which brings us to my favorite part…finishing the wall in plasters.
I’ve stood inside many a straw bale building and they are lovely- especially the ones with a living roof. Organic buildings have a different feeling to them altogether from conventional 2×4 and drywall construction. There is no comparison really. I’m ridiculously tactile and earthen plasters (otherwise known as adobe or clay) are my absolute favorite and can be applied directly to the bales without the aid of chicken wire although it will still be three coats (the scratch coat, the second coat, and the finishing coat). I’ve heard that a lime plaster should be the last coat on an exterior wall to cut down on the maintenance however, one should expect the occasional repair as walls tend to crack with the flux in temperatures between hot hot hot, and cold cold cold.
Having said that, it’s time to look at the Pros and Cons of this structure so hold onto your hat.
Advantages with Straw Bale construction:
- Straw has low embodied energy compared to standard wood frame houses insulated with fiberglass batting
- Requires far less lumber than standard wood frame construction thus reducing deforestation
- Straw bales are reasonably easy to acquire just about anywhere in North America
- Straw is an abundant and easily renewable resource
- Using the straw bale for construction instead of traditionally burning it after the grain is harvested prevents enormous air pollution.
- Straw bale walls are safe, strong, and long lasting
- Extraordinary insulation to thermally stabilize the inside environment (cool in the summers/warm in the winters)
- Due to this thermal stability less energy is required to heat or cool the home thus lessening our dependence on the evil empire (oil) and all the damage it does to Gaia (Mother Earth).
- Lowered heating and cooling costs save $$$
- High insulative qualities also are excellent sound proofing
- Straw bale construction can be built with simple tools and relatively untrained labor. DIY can learn a lot over a weekend workshop to apply to their own project.
- Straw Bale is conducive to community building as an owner/builder project
- This method is flexible to a variety of styles, and can be used in conjunction with other biotecture such as rammed earth or cob.
- The finishing stuccos and plasters make the walls fireproof, rodent and insect proof, and resistant to rotting
- When covered with plaster, straw bale resemble thick adobe walls
- Straw bale has become more widely known and accepted making it easier to obtain mortgages, building loans, insurance, building permits…in fact Vancity in North Vancouver, BC has approved them.
- Construction crews targeting this form of building are popping up making it an option if you don’t want to build it yourself.
Disadvantages with Straw Bale construction:
- There are still places that consider straw bales unconventional and so getting approval for permits, financing, and insurance may be a challenge.
- Using straw for building material takes away the practice of burning it in the field or ploughing it under which has the flip side of being a great way to replenish the nutrients in the soil for next years’ crop.
- Straw bale walls MUST be protected from moisture to avoid mold and rotting. If this occurs it is hell to repair. Sometimes the entire wall must be taken out.
- Straw bale walls need a thicker foundation than conventional wood beam homes so that adds to the cost of the project.
- While bales are easy to erect, they aren’t the most expensive part of construction in the totality of the project so very likely you won’t save money building a house of this nature.
- Due to moisture considerations a straw bale home can’t be built underground or earth bermed thus eliminating the thermal advantages of doing so.
- This construction method is still relatively new as it undergoes resurgence in popularity, therefore as it evolves, information changes, and therefore there is some risk involved as techniques are found to be inadequate or improved upon.
- As the methods change and opinions vary on different ways of working with straw, it is difficult for the newbie to decide which ideas to go with.
Just in case you want a little more to stuff your head with here’s a few leads to help you on your way:
• The Straw Bale House by Athena and Bill Steen, and David Bainbridge
• Build it with Bales: (a Step by Step guide to Straw Bale Construction) by S.O. Macdonald and Matts Myhrman
• Serious Straw Bale: A Home Construction Guide for all Climates by Paul Lacinski and Michel Bergeron
• Building with Awareness(construction of a hybrid home) with Ted Owens
• ‘The Last Straw’ is an American trade rag. That contains a wealth of information including codes, contacts, research and testing, latest techniques and bale suppliers all over the U.S.. They advise readers outside the U.S. to check with national straw bale organizations to obtain listings for the above.
On Vancouver Island, B.C. we are blessed with workshops hosted by ‘Our EcoVillage’ on everything from straw bale, and cob to permaculture. Check out their ongoing schedule of events if you wish to attend.
As yet we do not have a Canadian Straw Bale Association however, we do have some organizing going on in the province of Ontario if you wish to contact them for more info: http://www.osbbc.ca/