What reaction occurs when SPF is applied in wet conditions?

When SPF, or Spray Polyurethane Foam, is applied in wet conditions, blistering can occur due to trapped moisture. The application of SPF requires a dry substrate to achieve proper adhesion and avoid issues during the curing process. When moisture is present on the surface, it can become trapped beneath the foam as it cures, leading to the formation of blisters. This phenomenon compromises the integrity of the roof system because the blisters can create voids and reduce the overall durability of the SPF application. The other options do not accurately reflect the expected outcome of applying SPF in wet conditions, as they suggest positive effects or no issues, which are not aligned with the reality of working under such unfavorable conditions.