Roof Ballast Rock

Stone ballast is no longer allowed by many building codes.

Roof ballast rock.

Despite the positive qualities associated with a ballasted roof system there are some challenges. Single ply roofing materials aren t self adhered nor are they sealed together in any way. Gravel ballasted roofs with sikaplan or sarnafil single ply membranes are conventionally installed. The stone ballast on a ballasted roof system is the only thing holding the roof system in place.

The single ply membrane and other roof components including thermal insulation are loose laid. 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. A ballasted roof means that the roof membrane is not anchored or adhered in any way to the decking material.

The gravel top coat is also extremely resilient to heavy foot traffic and high wind scenarios. Ballast stone can crush the underlying insulation creating weak spots in the roof membrane. Next the membrane is rolled over the insulation 2. The ballast is used to keep the roofing system cool and of out of the sun s harmful rays thus keeping energy costs down.

It is however ballasted generally with gravel. The insulation is loose laid onto the decking. Over time the stones move around creating bald spots where the system isn t held down at all.