What happens if the existing roof has two or more applications of any type of roof covering?

When a roof already has two or more applications of any type of roof covering, building codes and industry practices generally prohibit adding new coverings over existing layers. This is primarily due to concerns about the additional weight, potential moisture issues, and the overall performance and longevity of the roof system.

Applying new layers can lead to complications, such as compromised drainage, increased heat retention, and a higher likelihood of failure of the roof assembly. Therefore, the best practice is to fully remove the existing layers before applying a new roof covering. This ensures that the substrate is properly inspected and repaired as needed, allowing for a more effective installation of the new roofing system, thereby extending its lifespan and maintaining its effectiveness.