FAQs for bale building
What about mice & other pests?
Mice aren't in fact a problem with bale houses; at least, no more-so than with standard houses. If mice are found in a bale house, they are more apt to burrow into fiberglass attic insulation or stud walls (easier to get into). Mice and other pests aren't attracted to straw as a food, since there is no nutritive value left in the straw.
What about fire?
Straw bale houses get a far better fire rating than standard homes do. They pass a 2 hour fire test. However, loose straw is very flammable, so great care must be taken to avoid activities producing sparks near loose straw. Good building practise includes carefully cleaning up the loose straw on the site at the end of each work day.
Fire Testing: SHB Agra Engineering and Environmental Services Laboratory in Albuquerque, New Mexico in 1993.
What if the bales get wet?
It is problematic in any type of building if the building materials get wet; at a bale raising, be scrupulous, and reject any wet or even slightly damp bales. If the bale wall gets wet during the construction phase, it does have the capacity to dry out through capilliary action, but if it is soaked, occasionally you may have to replace a portion of the wall during construction. Proper building techniques must be strictly adhered to when building with bales, including having large overhangs around the building, and the placement of the windows flush to the outside of the building. The CMHC have done several tests on moisture in straw bale buildings, and the conclusions are that moisture damage occurs with improper building practises.
What is the cost?
This is one of the first questions people ask...naturally. The biggest savings when building a properly detailed natural building are in the energy savings over its lifetime.
The cost of building a straw bale building varies greatly depending on design, size, and amount of hired labour. The price of a straw bale home is comparable, and sometimes less, than a custom, conventional home. However, when comparing, remember that a straw bale wall has at least double the insulation of a standard framed house, so the comparison isn't really accurate. If you were to ask a conventional builder to quote on buiding an R-30 wall, the square foot cost would be significantly higher.
Some folks will have you believe that you can build a straw bale home for $10/sq. ft. Somewhere out there, perhaps several decades ago, some owner/builders succeeded in building small buildings with no hired labour, and with reclaimed materials, for that cost, but would be near impossible to do today. Some owner/builders have been fortunate enough to build for as little as $60-$80/sq. ft. (that is with LOTS of donated labour), reclaimed materials, wood off their own lot, etc. With the tremendous increase in materials costs today, the average home, with hired labour, falls in closer to $200-250/sq. ft., and of course, depending on the design and finish, the cost can go much higher than that.
To keep costs down, start out with a simple design, if it suits your purposes. Try to keep the building as small as manageable for your needs. And if you are able/interested, try to schedule in some volunteer labour if possible.
What is the difference between straw & hay?
Straw is the left-over stalk after grain has been harvested. Chemically straw is composed mostly of cellulose and lignin, the same major components of wood. It contains no nutrition, and is used as bedding for livestock. Hay is field grass that has been cut and baled while still quite green. Hay has a high nutritive value (it is fed to livestock). People often confuse straw and hay; houses are made with STRAW. Some folks also confuse the spontaneous combustibility of hay with straw. It is the moist hay bales, heated under the right conditions, that can self-combust, not straw bales.
What kind of straw is appropriate?
Straw that is used for building can be harvested from various crops such as: wheat, oats, barley, rice, rye, hemp or flax. The kind of bale you choose is less important than the quality of the bale. You must use dry, tight bales. We recommend that you use bales from a local farmer whenever possible, to avoid large transportation costs (both environmental and monetary!).
How strong is a bale wall?
There has been a lot of testing on the compressive strength of bale walls, in addition to the lateral & sheer strength. Bale walls surpass many other building materials in this regard. In addition, the bale wall, once the plaster has been keyed into it, becomes a solid unit which acts as a stress skin panel.
What is the insulative value of a bale wall?
Again, a lot of testing has been done in this area. The R-value of a bale wall is approximately R-30, although some tests out there have it at R-50. We feel comfortable with using R-30 as the rating for the wall system. These figures are attainable with good building practice.
How long will a bale home last? Won't the straw decompose?
Straw is nearly the same as wood chemically, hence because we use sound building practices the home will last accordingly. The straw won't decompose any more than wood would decompose if careful attention is paid to proper detail. Many examples of strawbale homes and churches approaching and exceeding 100 yrs are in excellent shape, and are still being lived in.
What about building inspectors & permits?
There have been many postive examples of building inspectors and and township officials across Canada in dealing with issuing permits for straw bale buildings. Straw bale construction meets all performance aspects of the code, and there have been very few refused permits in Ontario to date, but there have been delays in some townships, and some building officials have put restrictions on projects that have made building with bales prohibitive. It's a really good idea to go to see your building officials well in advance of your project, equipped with lots of literature (of course, we'd recommend that you present your building official with a copy of our book, Straw Bale Building) and any other publications you have on hand that explain and legitimise building with bales. You can direct your building official to the research that has been done through the CMHC. The OSBBC (Ontario Straw Bale Building Coalition) will be conducting research and publishing reports on straw bale data in Canada in the near future.
What about building codes?
As mentioned above, building with bales meets all aspects of the code in Ontario. In general, building officials will want to see a set of finished plans that have been stamped by a structural engineer. On homes carrying an engineer's stamp, the building inspector will likely be more worried about the home meeting appearance bylaws than structural integrity. We can make referrals to engineers who are familiar with straw bale construction to prospective clients.
What about wiring & plumbing in the wall?
As with conventional building, you want to keep plumbing out of the exterior walls of the house. Plumbing fits into bale houses either in interior stud walls, or coming up through the foundation.
Electrical wiring can be done in several ways. Some folks run conduit through their straw bale walls, and then feed the electrical wire through that. Although this is perfectly acceptable practise, it is unnecessary. Some people prefer to build (or buy) a base board 'box' to house any electrical wiring at the base of the bale wall. This allows easy access for updates, computer wiring changes in the household, etc. A less expensive, but common way to run wire through a bale wall is to have your electrician come prior to the bale raising and install the electrical wire around the house, leaving ample wire for snaking up between the bales to reach the height of switches & plugs. As the bales are being stacked, the electrical wires are embedded 8"-9" into the bale wall, to be set at the appropriate height. (The electrical boxes can be attached to wood scraps that act as spikes, to set them in place until they are plastered). We recommend a gas-tight type of electrical box, 11 10 utility box, or masonry box which has a flange on it. The gas-tight box is sealed to air leaks, and you won't have to fool around making vapour barrier 'hats' behind each box.
How do you hang things on a bale wall (cabinets, pictures, etc.)?
Easy! All you need is a drill & a masonry bit of the appropriate size. Drill in through the plaster with the drill bit, and then you can put your screw right into the wall. Actually, we've used a cordless drill & have driven screws directly through a finish plaster and into the masonry below without pre-drilling for hanging pictures, and that worked fine.
For hanging cabinets and heavier items, it is best to plan this out ahead of time and imbed a piece of lumber into the bale wall, and plaster up to or over it. You can leave a couple of screws sticking out of the piece of wood for ease of finding it after you have plastered.
How do I convince family & friends that I'm not crazy?
Well, that's a tough one! Of course, we recommend that you share your copy of More Straw Bale Building and any other good books that you may have, but the best way to convince the non-believers is to take them on a tour of a couple of bale houses. The OSBBC hosts an annual province-wide tour of bale buildings, and apart from that, there are other public straw bale tours offerred throughout the year (the Robins' Nest B&B, near Norwood and in the Ottawa Area: Seventh Generation).
Is it possible to get a mortgage to build a bale building?
Many straw bale homes in Ontario have been built with a conventional mortgage. Once again, as with the building officials, you may have to do some educating at the bank. Be patient; if one bank refuses you, there will be others who will accept you as a client. The OSBBC will be posting information regarding banks who have issued mortgages for straw bale buildings in the near future. There are also other, more creative ways to obtain a mortgage as well.
Is it possible to get house insurance for a bale building?
As with the mortgage, yes, of course it is possible. In fact, the insurance companies are mainly interested in date regarding the fire rating of straw bales, and once they have seen the research, some clients have even been issued better insurance rates than a conventional house.
Where in the world have bale houses been built?
A better question would be where in the world haven't they been built. Honestly, bale building is enjoying a resurgence around the world. If you aren't a subscriber, the Last Straw Journal is an excellent way to keep in touch with straw bale building practises around the world.
What about bugs?
Once a bale building is properly sealed in, there shouldn't be any problems with pests, since there isn't any nutritive value in the straw itself. That being said, a select few owners of bale homes have, in the first year of the house, been annoyed by tiny beetles (either plaster beetles or collimba, not sure which)...these tiny bugs seem to lay their eggs on certain types of straw, and it seems that straw that has been harvested the same year as building is more likely to have the pests. Although harmless, the bugs are annoying. However, the good news is that after the first year, they die off, and you don't tend to ever see them again (by the way, in doing a search of plaster beetles, I discovered that this is not unique to bale buildings only; new construction, with lots of moisture & humidity caused by plastering, is susceptible to them).
What kind of foundation do you need?
A regular foundation...it can be a pier foundation, slab on grade, footing and frost wall, whatever suits the site. In some cases wood floors have the second joist in doubled to help carry the inside plaster skin. What does it cost to build a straw bale house? Is it less expensive than conventional building? Ahhh, one of the first questions people usually ask (and we've purposely buried it here in the middle of the FAQs!). If you are hiring someone to build your house for you, you aren't going to see a huge savings in the cost of the building. A custom bale house generally costs a bit less than a custom conventional home, but keep in mind that you're comparing apples to oranges: a bale house has twice the R-value of a conventional house; a more valid comparison would be to ask a conventional builder to quote on building a wall system of R-40. The biggest savings in a straw bale home is in its energy costs for the rest of its life. It will require significantly less energy to heat, and will remain relatively cool in the summer.
What other finishes can you put onto bale walls besides cement?
You can apply lime, gypsum, or earthen plasters on bale walls. It is important to use materials of similar permeability on the inside and outside walls. Some folks opt to paint the interior bale walls once they are plastered; it is important to use a water-based paint, and not an oil-based one. The best option would be to paint on a tinted lime-wash as a finish as these have the least effect on wall permeability.
If you're not a fan of a plaster finish, it is possible to strap a bale wall and then apply boards or other finishes, but you must first apply at least a base coat of plaster to seal the straw to provide fire protection.
Why build with bales?
There are many different reasons people choose to build with bales. From an environmental perspective, bales are an anually renewable building material, which happens to be essentially a waste product in Canada.
Bale homes are the likely choice for those who understand and care about embodied energy of materials. There are huge energy savings in bale buildings, given that the R-value of the walls is rated at R-30; this allows for great savings in heating and cooling buildings. Some people choose to build with bales due to the ease with which this technology can be learned.
It is an extremely accessible form of building, for men, women, childen, and people of all abilities.
A common reason for building with bales is the aesthetic value. If you have not seen a bale building, we encourage you to look for Open Houses and house tours. The warmth and depth of a bale wall is inviting, and inspiring. The rounded windows, built in benches, niches, the thick walls that serve to create warmth and quiet, the fact that no two bale houses will ever be the same...all of these are reasons enough to build with bales.
How are the bales used in construction?
Depending on the site and design considerations, there are two main types of construction with bales: structural, or load-bearing, and a framed structure using the bales as infill. Bales can be used structurally to hold up the roof of the house. To do so, in general, the wall system is erected first, a top plate is placed on top of the exterior walls, and the wall is compressed. Compression can be done many different ways, from threaded rod to using galvanised wire. The method we most commonly use is to loop 9 gauge wire around the top plate and through the foundation, which we cinch down using a come-along. The compression is done approximately every 4 feet (except where windows & doors prevent this from happening). Once the walls are compressed, levelled & straightened, we plaster them right away before putting on the roof or floor joists, depending on the size of the building.
The other method of building with bales is to erect a structure first (either timber framed, or modified post & beam), with the roof put on ahead of time, and then the bales are put into place as infill.
Clients often ask which method we prefer; we'd have to answer that it depends on the circumstances. A load-bearing design goes up wonderfully in good weather, and is easier to achieve with smaller buildings. However, if a build is postponed until the fall (which happens more often than you'd think!), it can be difficult to find a few consecutive dry days in which to safely erect the walls in our northern climate. Of course, there is always extensive tarping with a bale building, whether the design is load-bearing or in-fill.
An infill building allows for easier tarping systems that can be attached to the frame of the building that can be raised and lowered as need be, and a dryer environment for erecting the walls. However, even with a post & beam design, you do have to protect the walls from driving rains.
Is it true that a straw bale wall breathes? How so?
A bale wall doesn't actually 'breathe.' This is a misnomer that is commonly applied to bale buildings. Bale walls are vapour permeable, meaning that they will allow vapour molecules (water and presumably voc as well) to travel through the wall by osmosis. This is a desirable quality and the walls should not be "bottled up" with paint or other less permeable coatings. Walls that actually breathe (air moves through them) will insulate poorly at best and at worst will rot as exessive moisture can be carried through air leaks at the top of the building envelope.
Are you restricted with design ideas when building with bales?
You are mainly limited in terms of your imagination. But the one question that people often ask is can you build a straw bale dome? We don't think so, not in a heating climate anyhow, the waterproofing and vapour pressure issues are contrary to each other in a dome.
What about the story of The Three Little Pigs?
No comment! Except to say that it's fascinating that everyone who tells a Three Little Pigs joke thinks they are the first one! (our stock answer is that the Three Little Pigs forgot to plaster the straw house)
Straw Bale Testing Sites:
Here are some sites with test results for straw bale building. In the future, the OSBBC website (www.strawbalebuilding.ca) will post Canadian testing.
Ecological Building Network, San Francisco (non-profit entity founded by Bruce King, structural engineer)
Fire Testing: SHB Agra Engineering and Environmental Services Laboratory in Albuquerque, New Mexico in 1993 (Development Centre For Appropriate Technology)