Repairing a Strawbale Home

after-sponge-coat
The home after we applied a thin lime plaster over all the repairs.

Our clients for this project had finished building their own straw-bale home in the mountains west of Boulder about a decade ago. However, the harsh mountain climate and some details of the design and material selection had led to failures in areas of plaster, particularly around windows and in places where the roof drainage lacked adequate gutter systems.

lime-stabilized
The lime-stabilized earth layer which was used to repair damaged areas of the home, seen as the darker, lower level in this picture, has been built out by the homeowner to the same level as the original lime plaster. Now it’s ready to get a thin lime plaster over them all, to blend the different sections of the home together.

We worked with them to come up with a solution that would allow them to participate in the repair work, while using our experience and tools to speed up the process and get the home ready for winter.

First steps were to remove the lime plaster where it had begun to delaminate from the clay plaster base coat below. This happens because of a reaction between the two materials that creates a silt layer which prevents them from bonding, weakening the walls. In some areas, water had eroded the clay base coats, and we needed to mix and apply a clay plaster to build out everything to the same level. Next, we mixed up an intermediate lime-stabilized earth plaster to apply on top of the clay base coat. This in-between layer helps bond the two materials by creating a transition. The homeowners applied both of these layers by hand after we mixed up several batches and staged them around the house. They also took the opportunity to enhance and add some sculptural elements, including the house number in relief on the side of the wall.strawbale-home-number

We also added metal flashing around windows and below siding to move any water running off the building out to the surface of the wall and keep it from infiltrating into the plaster again. A final sponge-finished lime plaster over the whole house covers up any differences between the old and new and seals boundaries to prevent water from eroding the surface.

strawbale-repairs-in-progress

We will be able to go back in the spring next year, once temperatures are consistently above freezing, to apply a final colored coat over their home.