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If you’ve ever seen a flat roof covered with gravel and wondered why, the answer is simple – it’s there to keep the roof in place. Stones have been used as roofing ballast since antiquity, and in its modern form, stone ballast goes back to at least the 1970s.
Ballasted roofs are typically multi-ply protected membrane roofs, and the stones serve to weigh the membrane roof down and keep it safe from temperature extremes due to direct sun exposure, as well as secure and immobile during high wind or rainstorms. While some roofs use flat concrete or stone tiles, gravel is an extremely common ballast type due to its low cost and versatility.
Stone-ballasted roofs are easy to confuse with BUR roofs, since the latter are also commonly topped with crushed stone or gravel; however, BUR roofs use small stones embedded in tar or asphalt in order to serve as protection from sun rays, whereas ballasted roofs use large, loose unembedded gravel in far greater quantities and weight (from 10 to 25+ lbs per square foot).
Gravel ballast has additional beneficial properties – it has been shown to greatly improve the thermal qualities of a roof. Between the heat absorbing capacity of stone and its insulating properties, gravel roofs are even competitive with white membrane roofs when it comes to cutting heating costs in the summer.
None of this helps, unfortunately, when it comes time to replace or repair the roof and tons of gravel have to be gathered up and disposed of. Removing ballast used to be a particularly tedious and heavy job when it had to be done by crews with shovels, but there’s a much better solution available today.
Nowadays, stone ballast is commonly removed using giant, truck-mounted vacuums. This sounds counterintuitive, but is actually very fast and efficient. A custom vacuum rig is parked next to the building, a pipe is cast from the truck onto the roof, and a crew member guides the vacuum attachment over the roof to suck up all the stone and deposit it in the truck’s storage containers.
Afterwards, the ballast can either be kept and replaced on the roof after work has been complete, or be disposed of at the client’s discretion.
Building owners are advised that ballast removal needs to be performed within several days of roof stocking, since a membrane roof may be damaged if left without ballast for too long.
Eagle Rivet corporation has stone ballast removal capabilities, as well as a great deal of experience installing, repairing and removing stone ballast roofing. Call us to receive a quote or schedule your stone ballast removal!