Wet application: dependent on substrate and weather

A site-applied layer bonds to what is there. That calls for a clean, sound substrate, an adhesion test on the actual membrane, the right thickness and an application window with suitable temperature, humidity and rain probability. Seams and moving overlaps are detailed separately. The advantage: the layer follows every shape and gets between hundreds of PV feet without cutting.

Dry installation: factory dimensions, but handling

A board arrives from the factory with fixed thickness and fixed properties. Work remains on the roof: delivery, distribution, sawing, fixing, staggering joints, covering before rain. Below a new membrane (DEK) this is a natural working pass; on an existing roof full of PV, board installation across the field is rarely practical, but at upstands and edges (WEER) it is.

Compare the same function

Roof waterproofing is something different from an additional mineral protective layer. An organic liquid-applied waterproofing may be perfectly suitable within a tested roof without being an A1 mineral product. So compare function, position, labour hours, weather dependence and the associated evidence, not the price of a bucket against the price of a board. Rule of thumb: roof open, cover board below the membrane; membrane stays, mineral layer on top after an adhesion test; edges and upstands, exposed board.

The installation that fits position, weather and evidence wins. Not the cheapest bucket or board.