Moisture Issues in Straw Bale Homes — What Should You Watch For?

Preparing Bale Walls for Moisture Management

When constructing straw bale walls, it’s essential to ensure they are properly prepared for moisture management. This involves applying a waterproofing layer to the exterior of the bales, using a breathable, impermeable material such as a wax or lime-based coating. A minimum of 2-3 coats should be applied, with the first coat applied to the bales before they are stacked, and subsequent coats applied to the exterior of the wall after the bales have been plastered.

Load-Bearing vs Post-and-Beam Construction

In load-bearing straw bale construction, it’s crucial to ensure that the bales are properly secured to the foundation and that the plaster is not applied too thickly, which can compromise the structural integrity of the wall. For post-and-beam construction, the bales can be secured to the beams, rather than the foundation, allowing for greater flexibility in design. In either case, it’s essential to allow for adequate ventilation and to ensure that the plaster is applied in a way that allows for moisture to escape.

Managing Moisture in Plaster and Walls

To manage moisture in straw bale walls, it’s essential to apply a breathable plaster, such as a lime-based plaster, that allows moisture to escape. The plaster should be applied in thin layers, with a minimum of 1/8 inch (3 mm) between each layer, to prevent the buildup of moisture. Additionally, it’s essential to ensure that the walls are properly ventilated, with a minimum of 1 square inch (6.45 cm2) of ventilation per square foot (0.1 m2) of wall area. Regular inspections should be performed to identify and address any moisture-related issues before they become major problems.