Straw-Clay & Infill Systems

This technique consists of surrounding a frame structure with a thick infill of the straw-clay mixture. The frame is usually fully expressed on the interior of the building to take advantage of the beauty of the timber frame joinery. A lighter frame of wood is built on the eventual outside face of the building as an anchoring system for the straw-clay walls. Loose straw and a clay slurry are mixed mechanically, then allowed to age for up to several days in order to allow the straw to absorb the extra moisture and thus create a stickier and more easily tamped mixture. For higher insulation values less clay can be used. Slip forms are set up between the framing members, and the straw clay mixture is tamped by hand in two-foot layers. Occasional horizontal members spanning between the exterior frame are placed in order to lock in the straw-clay mass. Once each layer is complete, the slip form is moved up and the next layer is tamped until the wall is complete. The walls are allowed to dry before final plastering occurs. Any shrinkage is taken up by stuffing more of the mixture into the cracks. Other materials that can be used as infill including wood chips or perlite with clay slip in a similar form-work.

Blue Heron Members who work with this method

For more information on finding a contractor to do this type of work for you, see our list of members below who specialize in this category. Click the name for more information.

Eric Nelson
David Hornemann