Why Do Buildings Have Gravel On The Roof

In the summer it gets pretty soft and if left to its own devices would flow to the lowest point on the roof.

Why do buildings have gravel on the roof.

Gravel is used on flat roofs for two reasons. The gravel prevents sun hail errant baseballs etc from damaging the membrane the all important moisture seal created by the tar paper and tar. Such structures include plumbing vents pipes gas lines and other building elements. 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.

Roof penetrating structures can cause leaks. Simple it protects the tar from the sun. The stones force it to stay put. The first is to protect the underlying layer of roofing materials on built up roofs burs and the second is to secure or weigh down the roofing material as is the case with single ply flat roofs.

Tar has a low melting point. Uv rays can break down and dry out the tar membrane causing the tar to crack some describe it as alligatoring. Flat roofs have one thing in common with sloped shingle roofs. They are especially vulnerable to leaks anywhere a structure rises up through the surface of the roof.

Gravel is placed onto built up tar roofs to protect the tar surface from the elements such as ultraviolet light heat from direct sunlight snow and ice. It also helps in evaporation of water from. New roof shedding granules it is normal for a new roof to have some level of granule loss. The light color rocks reflect the sun s rays and heat.

You may be wondering why some buildings have gravel on the roof. There are different types and weights of gravel used on flat roofs for these purposes. To protect the underlying layer of roofing materials as is the case with built up roofs burs. This is due in part to the installation process where handling and walking on the shingles dislodges granules from the asphalt.

The layer of gravel on a low slope flat roof is used to help keep the underlay fabric secured and to provide some protection from the elements and human interference. The stones keep the tar paper in place and prevent it from buckling or blowing away in a high wind. This roof type is typically composed of overlapping layers of tar paper or rubber sheeting separated by tar.