Roof Ballast Rock

Over time the stones move around creating bald spots where the system isn t held down at all.

Roof ballast rock.

The buildup is ballasted with a gravel layer of at least 50 mm and 80 kg m 2. Ballast is commonly used with roofs made of tar and gravel roof alternatives including ethylene propylene diene monomer epdm polyvinyl chloride pvc and thermoplastic polyolefin tpo single ply flat roofs. The ballast is used to keep the roofing system cool and of out of the sun s harmful rays thus keeping energy costs down. A ballasted roof means that the roof membrane is not anchored or adhered in any way to the decking material.

When the concept first came to the u s plenty of roofers scratched their heads and wondered how the roof stayed on without being anchored especially during high winds or storms. Stone ballast is no longer allowed by many building codes. There are no fasteners installed at all 3 and 4. Single ply roofing materials aren t self adhered nor are they sealed together in any way.

The insulation is loose laid onto the decking. In windy areas ballast stone can actually blow off the roof creating projectiles below. It is however ballasted generally with gravel. Despite the positive qualities associated with a ballasted roof system there are some challenges.

Ballast stone can crush the underlying insulation creating weak spots in the roof membrane. The stone ballast on a ballasted roof system is the only thing holding the roof system in place. Gravel ballasted roofs with sikaplan or sarnafil single ply membranes are conventionally installed.