At Home with Natural Plasters

I began plastering straw bale buildings in Ontario almost 20 years ago. Bale building has its roots in the Sandhills of Nebraska in the early 1900s, and it had a global renaissance starting in the 1980s. The only reference in popular culture to straw bale building at the time I started was the story of the three little pigs, so we used to hear some variation of a big bad wolf joke on almost every job site. Our standard reply was, “The first little pig forgot to plaster his house.”

There’s a lot of truth to this, because most of the strength, weatherproofing, and air-sealing in a straw bale home comes from the plaster. When engineers are approving a load-bearing straw bale building, one of the most important numbers is the compressive strength of the plaster. And what about the famous insulation value of straw bales? Every now and then, an owner-builder tries to overwinter in an unplastered bale house. On a windy day in the dead of Ontario’s winter, you’ll find them huddled under a blanket, with the temperature in their house hovering above freezing. But the following winter, when their house is wearing its draft-proof coat of plaster, it’s the most comfortable and efficient home for miles around.

Traditional Techniques Meet Modern Methods

Plaster is typically made of sand, fiber, water, and a binder. The binder is what defines the