What Is a Roof Ballast Paver?

Ballast

• The word “ballast” originated in nautical parlance, but carries a generic definition in modern times. Basically, ballast constitutes something used to stabilize something else. More specifically, it may refer to something heavy used to lend stability or control to a vessel or building. A weight used to stabilize a boat or a hot air balloon, for instance, comprises one form of ballast. Ballast may also refer to gravel or stones used in a railroad bed or as an ingredient in concrete.

Ballasted Roofs

• Ballast shields roofs from elements such as rain and snow, and provides support for the weight of people standing or moving on the roof. Ballasted roofs contain various layers of material, including concrete, a vapor barrier for moisture protection, insulation, waterproof membranes, and gravel or small stones. This gravel resembles the ballast used on railroad beds. The only ballasted roofs are flat roofs. Green roof systems, or those with vegetation, exist on ballasted roofs.

Roof Ballast Pavers

• Roof ballast pavers differ slightly from ballasted roofs. They constitute pre-made construction materials designed for placing on a roof to provide protection from the elements and to support the weight of human traffic. Basically, roof ballast pavers are concrete-composite blocks or boards that fit onto roofs to provide some of the protection of a ballasted system without the complexity or cost of installing a fully ballasted roof system. Roof ballast pavers can cover entire roof surfaces or simply create walkways on roofs to support maintenance workers.

Built Up Roofing

• Built up roofing presents an alternative to ballasted roofs or roof ballast pavers and predates both of these systems. Usually described as tar and gravel roofs, built up roofing incorporates layers of asphalt laced with stones or pebbles. This mixture, which may also include strengthening materials such as fiberglass, protects roofs from blowing away in strong updrafts and provides protection from UV light. Built up systems contain smaller stones than ballasted roofs, but provide less support for weight on a roof than ballasted systems or roof ballast pavers.