Quick Answer
Seal straw bale walls with a combination of natural and synthetic products, including natural hydraulic lime, lime-based plasters, and borate-based solutions, to prevent moisture and pest damage, while ensuring breathability and structural integrity.
Applying a Protective Layer
To effectively seal straw bale walls, apply a protective layer of natural hydraulic lime (NHL) or lime-based plaster on the exterior surface. This layer should be at least 1/4 inch (6 mm) thick and should be applied in multiple coats, allowing each coat to dry before applying the next. The NHL layer helps to repel water, reduce moisture absorption, and prevent pest damage.
Borate-Based Solutions for Pest Control
In addition to the NHL layer, apply a borate-based solution to the straw bale walls to prevent insect and rodent infestations. Mix the borate solution with water according to the manufacturer’s instructions and apply it to the walls using a spray bottle or brush. The solution will penetrate the straw bales, providing long-term protection against pests and helping to extend the lifespan of the wall.
Final Sealing and Maintenance
Once the NHL and borate-based solutions have been applied, seal the straw bale walls with a breathable, synthetic coating such as a silane-based sealant or a polyurethane-based coating. Apply the sealant in multiple thin coats, allowing each coat to dry before applying the next. Regular maintenance is crucial to ensure the integrity of the wall, including inspecting the walls for signs of moisture or pest damage and making repairs as needed.
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