Of course flat roofs are not flat but have a very slight roof pitch of between 1 4 to 1 2 per foot.
Purpose of gravel on flat roof.
Gravel is used on flat roofs for two reasons.
A flat roof is a roof which is almost level in contrast to the many types of sloped roofs the slope of a roof is properly known as its pitch and flat roofs have up to approximately 10.
It provides excellent protection against uv rays and is an attractive option for windows and decks that overlook the roof.
Parts and composition of tar and gravel built up and flat roofing systems with a helpful tar and gravel roof construction diagram.
One is to act as ballast to weigh down the covering surface and help prevent it being blown off in high winds.
Advantages of a tar and gravel roof.
Built up roofing bur was the most common type of flat roof before modified bitumen and membrane roofing were developed.
Also a tar and gravel roof is very rugged and safe to walk on.
A flat or low slope roof is often not a suitable surface for shingles or other roofing materials because moisture can t flow off them.
One solution to this is a built up or tar and gravel roof where many layers of hot asphalt or bitumen tar paper and a waterproof membrane are applied and then covered with gravel.
Just enough slope to drain water but also flat enough to be a problem if not constructed properly.
Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof flat roofs or low slope roofs are also commonly found on commercial.
Built up roofs or burs also called a tar and gravel roof is a well established and popular style of flat roof that is made up of alternating layers of roofing felt or fiberglass and asphalt that is applied with heat which combine to make a long lasting sturdy roofing system.
The purpose of gravel on a flat roof.
On many flat roof low slope commercial buildings it s common to see gravel on top of the roof.
Flat or almost flat roofs can collect a tremendous amount of water especially if their outlets or downspouts become plugged with leaves and debris.
A bottom layer or two of insulation board multiple intermediate layers of tar or asphalt alternated with layers of roofing felt and a top layer of gravel.
Of all the flat roofing options a tar and gravel roof is the most economical.
A gravel or pea shingle on a roof serves two purposes.
Gravel is an excellent fire retardant.