Why Do Buildings Have Gravel On The Roof

Gravel is used on flat roofs for two reasons.

Why do buildings have gravel on the roof.

Walking on the tar would hurt the tar s seal fast. We recently had the building regs inspector around to sign off the extension we have had built. They are especially vulnerable to leaks anywhere a structure rises up through the surface of the roof. Per square in heavier than before.

The only purpose of rock on a membrane roof is to hold the roof system down. To protect the underlying layer of roofing materials as is the case with built up roofs burs. The gravel embedded on the top coat of asphalt the flood coat protects the underlying layers from the elements including ultraviolet rays and natural threats like roof hail damage or heavy rains. The gravel covers a tar roof.

To weigh down or secure the roofing material as is the case with single ply flat roofs. Roof penetrating structures can cause leaks. Tar and gravel roofs add substantially more weight to the building structure. There are different types and weights of gravel used on flat roofs for these purposes.

He told me that i needed to lay some gravel on the flat roof. Walked on gravel tends not to hurt the seal of the tar underneath. In a typical tar and gravel roof which by the way is gradually being supplanted by gravelless roof systems you put down a layer of tar paper then tar and finally gravel. Gravel surfacing on a asphalt built up roof system is embedded in asphalt above the felt plies.

Tar has a low melting point. As gravel cannot protect tarpaper surfaces where they rise vertically from the roof such as on parapet walls or upstands the felts are usually coated with bitumen and protected by sheet metal flashings called gravel stops. In the summer it gets pretty soft and if left to its own devices would flow to the lowest point on the roof. This surfacing keeps the felts protected from the sun s uv rays which damage the felts over time.

Such structures include plumbing vents pipes gas lines and other building elements. After you add the layers of tar supporting fabrics and the top layer of gravel your roof can be an extra 5 10 lbs. Flat roofs have one thing in common with sloped shingle roofs.