Veritas Viridis – 7- Julia’s Straw Bale Crash Course

Fourteen years ago I undertook a demonstration project, ‘Straw bale construction on small urban lots’, in an effort to make affordable ecological construction techniques more accessible and to encourage social sustainability and urban densification in downtown Montreal through the development of small, tranquil, semi-abandoned lots. In May 1999 the resulting straw bale house–the first in urban Canada—hit the media like wildfire (this pun intended!).  Contrary to popular perception and the lesson of the 3 Little Pigs (which was referred to ad nauseum), straw bale construction is highly fire resistant and insulating.

Over the next decade I received a lot of media attention, and countless phone calls and email requests for technical advice.  Most non-media inquiries were by ecologically-minded people initially attracted to straw bale by abundant claims of its affordability made by others;  very few, if any, had considered hiring an architect to help them design and build their home and were therefore unprepared for fees associated with ‘specialty’ construction (unprepared to spend even a modest amount on consulting fees). Everybody loved both the story and the rustic appeal of the house itself, but hardly anybody actually committed to building with straw bale —in fact we can count only two clients in addition to the straw bale project already begun at the time with the Mohawks of nearby Kahnawake.

For those enamoured with artisanal natural building techniques, straw bale construction is worth serious consideration:   straw itself is inexpensive, and fun and simple to install, offering a myriad of ecological benefits from carbon sequestering, low embodied energy and waste reduction to high insulation value and indoor air quality.  However, the laying of bales is only a small component of strawbale house construction:  much more complicated are the stuccoing of the bales inside and out and the marriage (joinery) of stuccoed bales with other building components. In fact straw bale construction presents numerous challenges which make it inaccessible to the average homeowner:  as an innovative building technique it is unknown to most homebuilders, designers, technologists and architects, and while conceptually it may seem simple (I thought so too when I first started!), the construction details are actually quite esoteric and fraught with potential hazards. Lack of air tightness and potential moisture damage are two important risk factors; self-builders, the most common proponents of straw bale construction, are particularly vulnerable to these risks due to their lack of technical experience, as attested by a number of CMHC (Central Mortgage and Housing Corporation) reports.

I got most of the details right on my house, and learned a lot in the process. I adore my straw bale house, would be hard-pressed to give it up, and would probably build with straw bale again if I had to do it over.  But on the flip-side, the house does have air tightness issues and the exterior stucco suffered from some initial cracking.  The lack of air tightness (around windows) can be avoided today through the application of non-toxic low expansion insulating foam (non-toxic wasn’t available back in 1999) The cracks—well, that’s a longer story, and before I get into it I would just like to thank artisane Sylvie Plaire and her colleague (assistant) Edyta…. for their skilful stucco repairs last fall.

Cracks appeared within the first year or two after construction at the corners of windows and in particular over the front and side doors.  Possible causes: structural movement (wood drying), lack of expansion joint at window frames, amateur stucco application skills, unsophisticated stucco recipe and lack of proper curing.

Being maintenance-averse and generally overburdened with other responsibilities, I put off repairs year after year.  Then one night last fall, around midnight, a resounding crash shook the house. I looked out the window in horror to see a car embedded in the wall by our front door!   The repair issue had just become significantly bigger and urgent.

Rapidly approaching cold weather and insurance claim procedures forced us into action, though we were despairing of not finding a contractor or skilled tradesman willing help us on such an unusual task – until we heard of Sylvie. In her confident hands the damaged stucco came off easily, leaving lyrical lines and whimsical shapes to be filled carefully with stucco mixes of varying lime content and texture (the first coat of course mixed with straw – so much more than we had put in our first coat 14 years ago – and worked into the surface of the bales by vigorous fingers!).

Small voids dating back to the original construction were filled meticulously with straw or mineral wool insulation to avoid overly thick stucco applications (another apparent cause of cracking), and fibreglass fabric and mesh were used strategically to reinforce transitions.  Our local lime plaster supplier used state of the art lab analysis to prepare a mix to match the original colour of the final coat, and in the end the repair work is noticeable only by its superior quality.

We were left with a few “take-aways” from this experience:

  • Straw bale is excellent at absorbing impacts from speeding automobiles
  • Opening up the wall demonstrated unequivocally that after more than a decade of exposure to Montreal’s intense climate, there has been zero degradation of the original straw bales
  • Even the car insurance’s adjuster presumed that straw bale construction is simple – it took some effort to convince him of the degree of specialization required for a satisfactory finish
  • Many daily passers-by still stop and admire the house, which radiates her charm all the more warmly since being spruced up after the accident.

– Julia Bourke

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About Peter Clark

An international leader in sustainable development and green design, Peter Clark brings a wealth of experience in resort, institutional and commercial development, renovations, property management and operations in Canada and Mexico.

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