What is the difference between mechanically attached and fully adhered roofing systems?

What is the difference between mechanically attached and fully adhered roofing systems?

• A. Fully adhered systems transfer load only via mechanical fasteners; mechanically attached use adhesives.
• B. Mechanically attached systems transfer load through fasteners, while fully adhered systems distribute load across the substrate.
• C. They are the same; no difference.
• D. Mechanically attached rely on adhesives; fully adhered rely on mechanical fasteners.

Answer: (B)

The key idea is how the roof membrane transfers wind and other loads to the building. In a mechanically attached system, the membrane is secured with mechanical fasteners that anchor it to the substrate; the uplift and load path go through those fasteners and their plates or clips into the structure. In a fully adhered system, the membrane is bonded to the substrate with adhesive across the surface, so the load is carried by the continuous adhesive bond and distributed across the bonded area rather than concentrated at individual fasteners. This difference in load transfer affects how the roof resists wind uplift, how it behaves with substrate irregularities, and how maintenance or retrofit work is approached. The other statements mix up the load paths or claim there’s no difference, which doesn’t match how these systems actually work.

The key idea is how the roof membrane transfers wind and other loads to the building. In a mechanically attached system, the membrane is secured with mechanical fasteners that anchor it to the substrate; the uplift and load path go through those fasteners and their plates or clips into the structure. In a fully adhered system, the membrane is bonded to the substrate with adhesive across the surface, so the load is carried by the continuous adhesive bond and distributed across the bonded area rather than concentrated at individual fasteners. This difference in load transfer affects how the roof resists wind uplift, how it behaves with substrate irregularities, and how maintenance or retrofit work is approached. The other statements mix up the load paths or claim there’s no difference, which doesn’t match how these systems actually work.