Roofing

In straw bale design, the roof plate acts as a plywood baffle or barrier which compresses above the top course of the bales which provides protection against rodents and moisture from possible roof leakage. It also needs to provide adequate structural support in order to transfer loads into the bale wall or the timber structure. Precompression support is necessary as the top plate is required to distribute the load evenly without considerable bending or twisting. The corners of the top plate receive an L-shape piece of plywood on top for extra stability and to maintain its form. 

A small wooden box beam is placed on top of the bale walls with slightly larger lumber attached to the side after the completion of compression. Similar designs also use wooden I-beams to create the box.