What type of single-ply roofing system typically uses both a base sheet and a cap sheet?

A modified bitumen (Mod bit) roofing system is designed to be a durable and flexible option for low-slope roofs. This type of roofing typically incorporates both a base sheet and a cap sheet, which are essential components that work together to provide enhanced protection and structural integrity.

The base sheet is applied first and serves as the foundation that adheres to the substrate. It provides initial waterproofing and a surface for the cap sheet. The cap sheet, applied on top, serves as the final protective layer, offering additional waterproofing and UV protection, while also improving the overall durability and longevity of the roofing system.

Mod bit systems are often reinforced with fiberglass or polyester, contributing to their strength and flexibility. This layering system of base and cap sheets is not only characteristic of modified bitumen but also essential for achieving the desired performance and lifespan of roofs in various climates and conditions.

In contrast, other single-ply roofing types like EPDM, TPO, and PVC typically consist of a single membrane layer, without the layered approach seen in modified bitumen systems.