Trivial Questions
Are straw bale houses more likely to have bugs than conventional houses?
Are mice and other rodents a problem in straw bale houses?
What happens if there is a fire in a straw bale house?
How much do straw bale buildings weigh?Regulatory Questions
How difficult is it to get a building permit for a straw bale building?
My building official wants me to get my drawings stamped by an engineer. What do I do?
My building official wants my drawings to be stamped by a designer who has a BCIN number. What do I do?
My building official wants plumbing drawings stamped by a plumbing designer. What do I do?
My designer doesn't live or work in the province of Ontario and doesn't have a BCIN number. What do I do?
My building inspector insists that I comply with BCC ruling 99-56-712. What do I do?
What if my building official wants conduit or BX?
What should be in my building permit application package?Plaster Questions
Is earthen, lime, or cement plaster better?
Do I need to install mesh over the stacked bales?
Should I use welded wire or plastic mesh?
Can I use chicken wire?
What if my plaster cracks.
Do I need two coats of plaster or three?
Can I plaster my house by hand?
Can my plaster be sprayed on?Straw Questions
What type of straw should I use?
Should I use rice straw?
Should I use hemp bales?
How can I tell if my bales are good?
How dense should my bales be?
Should I design my house around the length of the straw bales?
Should I pin with rebar or bamboo?Finish Questions
What type of finish can I get on a straw bale wall?
Can I cover my straw bale walls with brick, stone, siding, etc?
Can I fur the interior walls and cover them with drywall?
Can I paint my straw bale walls?
Do I need a heat recovery ventilator (HRV) in my straw bale house?
Will I get a better finish by colouring my plaster or painting it?Financial and Insurance Questions
Can I get a mortgage for a straw bale building?
Can I get a construction mortgage to build a straw bale house?
What if my bank won't give me a mortgage or a construction mortgage?
Can I get insurance for a straw bale building?
Can I get builders risk insurance for a straw bale building?
What if my insurance company won't give me insurance or builders risk insurance for my straw bale building?
How much money can I save by building a straw bale house?"How do I...?" questions
How do I run electrical in the straw bale wall.
How do I run plumbing in my straw bale wall?
How do I attach (a or) cabinet(s) to the wall or hang pictures?
What type of footing can I use for a straw bale building?
Can I build a straw bale building on a basement?People Questions
My [insert title] says [insert inane comment] about my plans to build with straw bales.
My real estate agent says no one will want to buy my house because it is made out of straw.
My real estate agent says that not having a basement will hurt my resale value.
Are straw bale houses more likely to have bugs than conventional houses?
In Ontario, and in many other places, immediately after plastering there is often a bloom of tiny black bugs. They are most numerous and most notable when the roof is on since this contains the humidity from the curing plaster within the building. Close on the heels of the little black bugs are larger tiny bugs called pseudoscorpions. Pseudoscorpions eat the small black bugs. As the house dries out and is cleaned periodically during the first few weeks of occupancy both types of bugs. Straw bale houses are no more or less resistant to insects than a stick framed or stone house in the same location. Spiders will crawl in. Ants come looking for food in the summer. Flies and lady bugs seek shelter in the fall.
Are mice and other rodents a problem in straw bale houses?
A well built and well maintained straw bale house is far less likely to have mice or rats in the walls than a stick framed house in the same location. Plastered straw bale walls must be maintained in a weather tight condition to prevent water damage so cracks and openings which would otherwise give rodents access must be closed up to prevent water damage to the straw. There are over 200 straw bale homes in the province on Ontario and there have been no reports of rodent problems.
What happens if there is a fire in a straw bale house?
Straw bale wall assemblies have been thoroughly tested in the United States, Europe, and Canada. In the United States straw bale wall assemblies plastered with cementitious plaster have achieved an ASTM E119 two hour commercial fire rating in both a small scale and a full scale fire test. A straw bale wall assembly plastered with earthen plaster achieved an ASTM E119 one hour commercial fire rating in a full scale test. In Europe straw bale wall assemblies have achieved an F90 90 minute fire rating. The testing in Canada was done by the National Research Council on behalf of an engineering firm which has declined to share the results. By way of comparison whereas a straw bale wall assembly easily achieved a ASTM E119 2h rating a 2x6 wall assembly suffered complete failure and the test was stopped after only 8 minutes.
How much do straw bale buildings weigh?
Straw bale wall panels using typical straw bales and a nominal 1.5" (3.8 cm) coat of plaster weigh about 60 lbs/sq ft (290 kg/m2) of wall.
How difficult is it to get a building permit for a straw bale building?
It is relatively easy. Straw bale construction is becoming more widely known. Many building officials have some knowledge of straw bale construction. We highly recommend that you approach the building officials in the municipality where you are thinking about buying property before actually buying the property. If they tell you that they will never consider approving a straw bale house you may want to consider taking your building permit fees, your development fees, your road access fees, a lifetime of 911 fees, school and property taxes to the next municipality over.
In most cases with some gentle persuasion and a lot of work to educate a building official who doesn't know about straw bale construction you can convince them that it will work and get your building permit.
My building official wants me to get my drawings stamped by an engineer. What do I do?
Get your drawings stamped by an engineer.
It is normal in the province of Ontario for a building official to ask for an engineer's stamp on your straw bale construction drawings. Well known conventional construction systems such as stick framing are included in the building code so it is not normally necessary to have drawings of conventional buildings stamped by an engineer. Building officials ask for an engineers stamp because it limits the liability to the municipality should you or any future owner experience a structural problem with the building.
If you need help finding an engineer who will stamp your drawings please visit the Ontario Straw Bale Building Coalition website or give us a call.
My building official wants my drawings to be stamped by a designer who has a BCIN number. What do I do?
Get your drawings stamped by a designer who has a BCIN number.
The recent changes to the Ontario Building Code (OBC 2006) require that the designer of any Part 9 residential building have a BCIN number. This is not a special requirement for straw bale buildings so you must have a BCIN stamp.
My building official wants plumbing drawings stamped by a plumbing designer. What do I do?
Get plumbing drawings made up and stamped by a plumbing designer.
The recent changes to the Ontario Building Code (OBC 2006) require that the plumbing designer for any Part 9 residential building have a BCIN number. This is not a special requirement for straw bale buildings so you must have stamped plumbing drawings.
My designer doesn't live or work in the province of Ontario and doesn't have a BCIN number. What do I do?
The rules about having drawings stamped by a designer with a BCIN number are very clear. You will have to find someone who will stamp your designers drawings for a fee or you will have to hire a designer who has a BCIN number to redo your design work.
My building inspector insists that I comply with BCC ruling 99-56-712. What do I do?
What if my building official wants conduit or BX?
Offer to use 12/2 instead of 14/2 for extra safety. Point out that the electrical code allows 14/2 and 12/2 to be run in an insulated space such as a wall cavity filled with fiberglass or the straw in a straw bale wall assembly. Point out that a 2x6 wall in (IS?) flammable and is completely gone during the ASMT-E119 test whereas a straw bale wall achieves a full two hour fire safety rating. If all else fails, use conduit or BX.
What should be in my building permit application package?
A good place to start is the website for your municipalities building department. Most building departments will have anywhere from some to a great deal of information about what should be included in your application package.
Township of Augusta Building Department
City of Ottawa Building Department
Is earthen, lime, or cement plaster better?
Earthen plasters and cementitious plasters (plaster containing a portion of cement, typically around 18%) both perform very well on straw bale wall assemblies. Earthen plasters typically use clay found on or near the construction site and are produced on location using sand which is often mixed with a fibrous material such as hemp hurd, cat tail fluff, or chopped straw.) Earthen plasters are made up of local materials so the plaster at each location will be different based on the type, quantity, and properties of the materials used. This means that each local plaster will mix, apply, and cure differently. Earthen plasters often require experience and skill to make them work well but they are better for the environment and for the people applying them since they do not contain cement or lime and require less energy to transport and store than bagged cement containing plasters.
Earthen plasters require very wide overhangs to prevent any exposure to precipitation.
Cementitious plasters come dry and bagged from a masonry supply or building supply store. They are mixed with sand and water on site and applied to the wall. They are much simpler to mix and apply and the results are consistent from building to building. Cement containing plasters are also much more readily accepted by building officials because they are an understood material. Much of the testing done on straw bale wall assemblies has been on walls plastered with cement containing plasters. Cement plasters contain cement and lime and therefore require precautions to be taken to protect against inhalation of fine the fine powder as well as exposure to the mixed plaster. Cement containing plasters are stronger than earthen plasters and tolerate wetting far better though it is still a good idea to protect your walls against direct precipitation exposure and splash back as much as possible.
Lime plasters can be just as tricky to apply as earthen plasters. Lime plaster consists of slaked lime and sand which is applied in relatively thin coats. Lime putties are more hazardous than cement plasters and contain far more embodied energy. Cement containing plasters typically have 16% to 18% cement and 16% to 18% lime whereas lime putty is 100% lime and lime plasters are typically around 50% lime. Lime has 90% as much embodied energy as cement and therefore a much thinner application of lime putty has just as much embodied energy as a much thicker and much stronger coat of cement containing plaster. We recommend that lime putties be applied only by experienced professionals.
Do I need to install mesh over the stacked bales?
Most building officials demand mesh on straw bale walls. A few buildings have been built without. There is a debate within the bale building community in Ontario about the need for mesh. Most builders believe that it reduces cracking and strengthens the walls. Some believe that it is a waste of time and money that adds nothing to the walls.
The installation of the mesh is very time consuming. The mesh must be pulled tight, securely fastened to the top plate, curb, and any vertical members then stitched tight against the bales with twine and a long needle. The mesh must be tight against the surface of the bales or it strips the plaster off the trowel and it walls to the floor rather than going onto the wall. Stacking the bale walls goes very quickly then your project seems to grind to a virtual halt while you spend weeks getting the walls finished and ready for plaster.
Should I use welded wire of plastic mesh?
This is very much a matter of preference. The usual welded wire used in Ontario is 2x4 welded utility fence which comes in 100 foot rolls three feet wide. This is cut into lengths as long as the straw bale walls are tall then fastened at the top pulled tight and fastened at the bottom. The seams between the strips of mesh must then be sewn together before the mesh is stitched.
The plastic mesh (often referred to as Tenax, the name of the manufacturer) is preferred by professional builders. It comes in a roll 10' wide and 330' long (3m x 100m) and is stapled to one vertical member then stretched around the house and stapled to the same vertical member. The plastic mesh is less stiff and therefore often requires more stitches to achieve the same tightness against the bales. It also has much smaller openings making completing the stuffing before the mesh is installed very important of the mesh will have to be cut to complete the stuffing.
You can but it tends to be difficult to handle, stretches and loosens, and doesn't really add much to your wall. No one has used chicken wire in Ontario for more than five years.
The short answer is "you fix it." Plaster cracks. Anyone who tells you that it won't is lying or doesn't know what they are talking about. Our experience here in Ontario has been that plasters crack during their initial curing period but almost never after the plaster is cured. Exterior cracks are now being repaired using plaster of Paris which is immediately treated with silicate paint to make it water-resistant. Interior cracks are easily repaired with fiberglass drywall tape and fast curing drywall compound.
Do I need two coats of plaster or three?
You need a nominal plaster thickness of 1.5”. This can be achieved with two coats of plaster or three. Most straw bale homes in Ontario now get two coats of plaster and a coat of silicate paint on the exterior and a coat of silicate, milk, or clay paint on the interior.
Can I plaster my house by hand?
Yes it is possible but no it is not practical. An 1800 square foot house takes a professional plaster crew of 8 people four long days to plaster using a mortar mixer and pump which sends the plaster to a slotted trowel. That is 32 long professional man days using professional equipment. Hauling plaster by hand takes much longer and requires excellent strength and endurance.
Yes. None of the professional plaster crews in Ontario are using sprayers anymore. They found that it took as long or longer to clean up the over spray after spraying than it did to actually spray the plaster. The new pump and slotted trowel system is faster and much neater.
What type of straw should I use?
There are plenty of “experts” who will tell you that one type of straw or another makes the best or strongest straw bales. Their preference often has more to do with their occupation (hemp farmer, wheat farmer, etc.) or their geographical location (in the rice belt in California) than with what straw actually makes the better walls. There is no testing to show that any one type of straw is superior to another. The best straw for your project is the kind that you can get locally that is well baled and dry.
If you live near a rice paddy and can get good rice bales, yes. If you live in Ontario it is going to be very difficult to find rice straw.
Hemp is an incredibly tough fiber. Hemp bales are incredibly tough to cut, shape, and retie. Most professionals working on buildings using hemp bales insist on having another type of straw available for cutting, retying, and shaping. If you like (LIVE?) close to a hemp farm and can get good hemp bales cheap, use them but buy at least 20% of another type of straw.
We've heard from people who have used hemp bales that they are very oily and that it can be difficult to get plaster to stick to the bales.
How can I tell if my bales are good?
Do they look good? Do they smell good?
Bales are good if they smell fresh and are bright yellow. If the bales smell damp or musty then you shouldn’t use them.
Straw bales have a cut side and a folded side and are typically tied with sisal, polypropylene twine, or wire. The cut side of the bales typically has a saw tooth pattern. Sharp cutters on the baler can reduce this effect. Wire tied bales are very difficult to cut and retie so most builders prefer sisal or poly tied bales.
None of the testing done here in Canada has shown any relationship between the density of the bales and the strength of the wall. All of the testing has been done using whatever bales are available locally using the "does it look good and smell good" method of selecting bales. The testing done at the University of Manitoba Winnipeg (straw bale walls are 10 times as strong as conventional walls) and at Queens University (the thickness of the plaster has far more effect on the strength of the wall than any other factor including the strength of the plaster) both show that straw bale walls are far superior to conventional walls with no consideration given to the type density of straw used.
If you pick up a bale by the strings (typically with your thumb under one string and the middle finger of the same hand under the other) and there is about the width of your other palm (around 4") between the strings and the straw the bales are tight enough for straw bale construction.
Should I design my house around the length of the straw bales?
This sounds like a great idea but it doesn't work. The length of bales from a single baler can vary dramatically. The baler ties and ejects the bale when it reaches a certain tension when it compresses the straw. This can result in a variation of up to six inches from bale to bale. There is simply no way to get away from retying bales. You can ask your straw supplier to make bales of different lengths so that you have a wider variation in the length of the bales and can pick and choose bales that fit a given spot. You're still going to end up retying bales.
Should I pin with rebar or bamboo?
Neither. Most advocates of pinning the straw bales believe that pinning will make the wall more stable until it is plastered and stronger once plastered. The loosely stacked straw bale walls are subject to being knocked over until the top plates are installed. This is generally done the same day or within a few days of stacking. What pining the bales does is guarantee that a wall that is knocked over accidentally will collapse completely rather than having a section collapse. Straw bale walls function as structural insulated panels with the straw insulating the panel and preventing the plaster from buckling and the plaster bearing the weight of the upper floors and/or the roof. Rebar or bamboo pins stuck in the middles of the bales won't strengthen the wall since any force strong enough to overcome the strength of the plaster and to cause it to fail will simply twist the internal pins out of the bales. What they do do is make the walls more difficult and time consuming to stack and they make it very difficult to adjust the wall once it is stacked because the pins prevent the bales from moving relative to each other before they are plastered.
What type of finish can I get on a straw bale wall?
The finish on a plastered straw bale wall is plaster. It is generally a fairly smooth light gray colour. Colourant may be added to the final coat of plaster. The plaster may also be chemically stained. Interior plaster may be covered with a vapour permeable interior plaster like drywall compound or pearlited gypsum plaster.
Can I cover my straw bale walls with brick, stone, siding, etc?
No. The straw bale wall assembly works well because the vapour permeable plaster is exposed on both sides to allow the easy migration of moisture. Adding a non-permeable covering will reduce the performance of the system and may result in the failure of the wall or building.
Can I fur the interior walls and cover them with drywall?
No, for the same reason.
Can I paint my straw bale walls?
Yes but you must use a highly vapour permeable paint. Milk paint, silicate paint, and non-barrier clay based paints are all excellent choices. Silicate dispersion paint is the paint of choice for the outside of straw bale houses in Ontario.
Silicate Dispersion Paint (inorganic mineral paint) uses potassium silicate as the binder. It bonds to your plaster by penetration and petrification (it soaks in then turns to mineral crystals.) It won't age or blister like non-silicate paints, sheds liquid water but remains highly vapour permeable to allow water vapour to pass out of your walls. It is like Gore-Tex for your house.
Will I get a better finish by colouring my plaster or painting it?
It is extremely difficult to get a consistent colour when using coloured plaster. Many people have tried. Very few have succeeded. You can achieve a much more consistent much more predictable finish using paint.
Can I get a mortgage for a straw bale building?
Yes. There are over 200 straw bale buildings in the province of Ontario and virtually all have mortgages. Those that don't have either paid off their mortgages or never had one to begin with.
Can I get a construction mortgage to build a straw bale house?
Yes. Many straw bale buildings in Ontario have been built with construction mortgages .
What if my bank won't give me a mortgage or a construction mortgage?
Why are you doing business with them? All banks and many credit unions in Ontario have financed one or more straw bale buildings. Your branch or the loans officer your file was referred to may not support your decision to build with straw bales. Shop around. There is someone out there who will be happy to help you with your project. I strongly recommend that you take all of your banking business away from the bank that told you no and give it to the bank that told you yes.
Can I get insurance for a straw bale building?
Yes. All but a few of the over 200 straw bale buildings in the province of Ontario have insurance. Those that don't either choose not to for political reasons or have basic safety issues which would prevent any home from getting insurance.
Can I get builders risk insurance for a straw bale building?
Yes. Many of the straw bale buildings in Ontario were built with builders risk insurance.
What if my insurance company won't give me insurance or builders risk insurance for my straw bale building?
Why are you doing business with them? All of the major and many of the smaller and mutual insurance companies in Ontario provide insurance for one or more straw bale building. It is possible that your broker of the loss prevention officer to whom your application was referred do not support your choice to build with straw bales. Shop around. You will find someone who is happy to provide insurance. I strongly recommend that you take all of your insurance business (automotive, home, health, etc.) away from the company that told you no and give it to the company that told you yes.
How much money can I save by building a straw bale house?
How blue is the sky? Straw bale houses are generally around 80% conventional. The interior walls, floors, and ceilings, the electrical wiring, plumbing, lights, appliances, heating systems, cooling systems, and other mechanicals, the roof, the foundation, the second floor deck, the windows, and the doors are all the same as they would be on a conventional house so that 80% of the project costs exactly the same as it would in a conventional house. Your building permit fee, development fee, road access fee, electrical permit fee, septic permit fee, electrical connection, septic system, and well also all cost exactly the same as they would for a conventional house.
Any savings that you realize will be in labour and contracting if you do some, most, or all of the work yourself and general contract the project yourself. You can also abuse your friendships and impose on family for cheap labour.
If you hire a contractor to build your custom straw bale home the cost is generally very similar to a conventional custom home of the same size and style in the same location with the same fixtures and finishes.
How do I run electrical in the straw bale wall.
Normal 14/2 and 12/2 electrical cable (Romex) can be run directly on top of the first course of bales. You pull out a loop of cable wherever you need an outlet then continue along the wall. Once you’ve got all your loops pulled out and stapled you continue stacking your walls. Vertical runs up to switches or up to the ceiling or second floor deck must be pushed into the bales.
How do I run plumbing in my straw bale wall?
You don’t. You are not permitted to run water supply or sanitary drain lines in an exterior wall. If you are passing a pipe through the exterior wall for a hydrant (an outdoor faucet for watering your lawn and garden) it can be run through in a larger PVC pipe and the space between filled with low expansion foam. Make sure to get the longest freezing protected hydrant that you can find. You want one that is at least 12” from the valve to the outlet and you want one with a draining siphon break.
How do I attach (A OR) cabinet(S) to the wall or hang pictures?
If you know the locations of your cabinets in advance you can place horizontal or vertical 2x4s in notches in the bales which then get covered with vapour barrier and diamond lathe and plastered into the wall. Later you can drill through the plaster then sink screws into the 2x4s.
To hang a picture drill a small hole into the plaster at a downward angle and slide in a small nail or the nail of a picture hanging hook. For larger items drill a larger hole, pump the hole fill of caulking, pound in a plastic concrete anchor then drive in a screw to the required depth.
What type of footing can I use for a straw bale building?
You can use any type of footing you like. Your foundation will have to be designed and stamped by an engineer to take into account local soil conditions, the additional load and wider load flows of a straw bale building.
Can I build a straw bale building on a basement?
Yes. Your floor deck will have to be designed to take into account the additional load and the wider load flows of a straw bale building.
Basements are often dark and damp and it has been our experience that they are most often used to store things that you would be better off getting rid of. Building and moving into a straw bale building is going to be a major life event for you. Why not take this opportunity to get rid of the things that you don't use and free yourself of that extra space that you rarely use but that you have to heat for the entire life of the building.
My [insert title] says [insert inane comment] about my plans to build with straw bales.
Yup. You're going to get that.
Are you related to them by blood? No? Shop around until you find someone who has a sense of imagination and who supports your excellent environmental and lifestyle choices. They are out there.
Virtually everyone you speak with will ask you if you've heard the one about the three pigs. You'll answer questions about bugs, moisture, and fire a million times (a conservative estimate.) It will begin to drive you crazy. Then, you'll start to quote numbers like $1 annual savings heating with natural gas reduces your annual CO2 emissions by 25.5 kg. A conservative annual energy savings of 20% (CMHC) can reduce the CO2 emissions from an average house by 1275 kg per year. The self satisfied smirk of the "three little pigs" jokesters will be replaced by a slack jawed realization that you may actually be on to something.
My real estate agent says no one will want to buy my house because it is made out of straw.
See the answer above. Would you buy your house because it is made out of straw? Yes? There are thousands of other people out there who would too. The fact that your real estate agent lacks imagination is a good reason to find another real estate agent.
My real estate agent says that not having a basement will hurt my resale value.
Do you ever plan to sell your house? If not, who cares what your real estate agent says?
Do I need a heat recovery ventilator (HRV) in my straw bale house?
Yes. Straw bale houses do not "breathe" (allow the passage of air from one side to the other.) They are "vapour permeable" (allow the slow movement of water vapour) and do allow some moisture to pass through the plaster. This vapour permeability is sufficient to deal with the normal drying needed to keep your straw bales in top condition but is not sufficient to remove the moisture from cooking, showering and breathing from your home. In order to maintain good indoor air quality you should install an HRV.
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