Why Do Buildings Have Gravel On The Roof

The gravel covers a tar roof.

Why do buildings have gravel on the roof.

This added weight can strain your roof underlying substrate and facility as a whole. The only purpose of rock on a membrane roof is to hold the roof system down. 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.

They are especially vulnerable to leaks anywhere a structure rises up through the surface of the roof. Per square in heavier than before. We recently had the building regs inspector around to sign off the extension we have had built. After you add the layers of tar supporting fabrics and the top layer of gravel your roof can be an extra 5 10 lbs.

Gravel is used on flat roofs for two reasons. Also the gravel acts as a wick to pull up any water left on the roof after scuppers or gutters lead excess water away. Gravel surfacing on a asphalt built up roof system is embedded in asphalt above the felt plies. This surfacing keeps the felts protected from the sun s uv rays which damage the felts over time.

To weigh down or secure the roofing material as is the case with single ply flat roofs. Such structures include plumbing vents pipes gas lines and other building elements. Walked on gravel tends not to hurt the seal of the tar underneath. 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.

Flat roofs have one thing in common with sloped shingle roofs. 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. 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. Can i use pea shingle size 10 15mm does anyone.

Tar has a low melting point. Walking on the tar would hurt the tar s seal fast. In the summer it gets pretty soft and if left to its own devices would flow to the lowest point on the roof.