Mineral-finished and sand-finished torch-on membranes may use similar bituminous technologies, but their exposed surfaces usually indicate different intended roles.
Mineral-finished membranes
A mineral cap sheet is commonly used as the exposed upper layer of a bituminous roof system. The granulated finish protects the bitumen from ultraviolet exposure and gives the completed roof a durable wearing surface. Colour, reinforcement, thickness, fire performance and system approval still need to be checked.
Sand-finished membranes
A sanded surface is commonly associated with an underlay, intermediate layer or a membrane intended to receive another compatible finish. It should not automatically be treated as an exposed cap sheet. The technical data and system specification determine whether it needs a coating, cap sheet or other protection.
The decision should confirm
- whether the membrane is an underlay or cap sheet
- APP, SBS or other bitumen modification
- reinforcement type and declared performance
- application method and substrate compatibility
- lap, upstand and termination details
- expected UV and weather exposure
- fire and warranty route for the complete build-up
A mineral surface does not make every membrane a complete roofing system, and a sanded finish does not make a product lower quality. Each belongs in the position for which it was designed.
Select the finish around exposure and its position in the system.