Why Put Rocks On Flat Roof

But such a low slope holds snow and water much longer than a steeply pitched roof and therefore needs a very different material to stay watertight.

Why put rocks on flat roof.

The purpose of stone or gravel ballast on a flat roof it is not unusual to find a gravel top coat on commercial roofing systems. Various types of rock are embedded into asphalt roofs to add strength to the roof and help it last longer. Some commercial single ply roofs are ballasted with gravel this report does not apply to these. 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.

Contractors and builders use gravel on flat roofing for two primary reasons. The gravel also acts as a protective measure to prevent natural debris such as leaves. Flat roofing is not actually flat. 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.

Because the gravel holds and releases heat the layer of gravel on a bur flat roof can both help water evaporate and. A wear surface of finely crushed stone granules is usually applied to the top layer of hot tar to protect the built up roof assembly from uv light and weather. If the roof is what is called a ballast roof it is not fastened or adhered down throughout the whole roof. In the summer it gets pretty soft and if left to its own devices would flow to the lowest point on the roof.

The stones force it to stay put. It has a very low slope between 1 4 to 1 2 inch per foot so that it drains water. Rocks are placed on commercial flat roofs for many different reasons. Then the rocks absorb a lot of heat into themselves and give it back off to the air after the sun goes down rising heat as does moves it away from the house.

Tar has a low melting point. Pea gravel crushed rock and decorative rock white quartz are often dispersed into a flood coat of hot asphalt and applied over the top of the roof membrane. The gravel provides a better grip for foot traffic when conducting maintenance or repairs.