Working in a structure with a curved upper frame adds a unique challenge to roofing, as we discover while trying to install roof boards. We originally attempted to use white vinyl boards, which we selected for their light weight and extreme flexibility. However, it turned out that this flexibility was, in fact, a detriment: even with a custom-built PVC support, we had great difficulty keeping the boards in the correct shape while attaching them, and found that, even when screwed in, the boards tended to bow downwards excessively. Thus, we switched to an alternative material, Coroplast, which is still extremely lightweight, but is significantly more rigid. We had much greater success using the Coroplast boards, and were able to (mostly) get in our interior roof!
Here are some links to materials we found worked especially well for the extremely tricky installation of a curved roof:
Coroplast 4′ x 8′ Corrugated Plastic Sheets: A lightweight but rigid board, which we found to be the perfect option for our roofing needs.
Scotch Extremely Strong Mounting Tape: We added strips of this super sticky tape along each of the metal beams and along board seams to complement the spray adhesive (see link below) and (hopefully) provide a strong, permanent solution for mounting the Coroplast sheets.
3M Hi-Strength “90” Contact Adhesive: This stuff is easy to apply, and, in our experience, works extremely well to bond most any surface to most any other surface. We used this in conjunction with mounting tape to adhere the Coroplast sheets to the curved roof interior.