The Evolving Straw Bale House

In previous postings we have discussed some of the design rationale and construction methodologies employed and advocated by our company. This is a more detailed analysis of technologies and materials used from foundation to roof.

Not too long ago the construction of a straw bale house involved the design of a custom foundation, sometimes complex and unorthodox framing, shimming trusses and rafters on an undulating box beam on a load bearing straw bale wall, and a host of other quirky construction methods not often encountered by professional builders and home owners. Part to our mandate has been to make straw bale construction simpler and more accessible.

Most of the homes we design are constructed on conventional basements; an eight inch concrete wall and strip footings with a standard I joist floor system. This is the same foundation most standard frame houses are built on. Even though the walls in a bale house are either fourteen or eighteen inches thick, our frame, a modified post and beam system, carries the majority of the structural loading of the building on the outer six inches of the wall, the same as a standard frame house. Interior walls are framed with standard 2×4 and 2×6 stud walls.

Windows and doors are secured in framed openings extending from floor to ceiling and the full depth of the wall, very similar to a frame house. Windows that ‘float’ or are suspended on a light 2×4 or 2×6 frame in a straw bale wall is not something we design or recommend.

Most of the roof systems for our homes are the same truss or stick framed systems you would find in a wood frame house, designed to fit on top of non -loadbearing straw bale walls and frame walls the same way they would in a conventional frame home.

Many of our designs would best be described as hybrids –  employing straw bale, conventional frame construction and where appropriate, the use of steel and concrete. Interior walls and ceilings are finished with drywall, locally-milled wood or the many other materials available in the marketplace.

Working with our design team partners, Acius Structural Engineering, Habib John Gonzalez (Sustinable Works), local suppliers, and truss and joist manufactures, we have developed load bearing, structural frame system that uses standard materials and building technologies available at any building supply centre or lumber yard. Plumbing and wiring require only minor modifications (if any) to be adapted to a straw bale house.

Engineered truss roof systems, joist systems and standard basement foundation round out the integration and relative ease of construction we strive to achieve for straw bale home.

The evolving design of straw bale homes is not to make building technology adapt to straw bale, but having straw bale adapt to modern building technologies and products for ease of construction and higher guarantee of a success in home building for novice ‘owner-builders’ and experienced contractor alike.

For more information on straw bale technology or our design services, feel free to contact us.

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McKernan Duo Project
McKernan Duo Project under construction, March 2013

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