Although the primary purpose of ballast is to weigh down the roofing materials it also offers similar protective benefits as described above.
Gravel ballast roof weight.
The stones used in ballasted roofing are generally 1 5 2 5 inches in diameter and applied in a thicker layer.
Ballast tar gravel roofing.
Gravel on a ballast roof system.
A built up roof for example will typically include the built up membrane itself with or without gravel as well as some kind of insulation and cover board which will vary in thickness from roof to roof.
Adds a lot of weight to the roof system typically 10 15 pounds per square feet.
Ballast stone traps a lot of dirt making patching difficult.
Gravel ballast of 20 40 mm diameter is required in order to provide resistance to the effects of wind scour bre digest 311 july 1988 refers which can easily remove smaller units from the roof.
Felt tar and gravel roofing 4 ply 5 3 lb m ft 2 25 9 kg m 2 felt tar and gravel roofing 5 ply 6 1 lb m ft 2 29 8 kg m 2.
Gravel ballasted roofs with sikaplan or sarnafil single ply membranes are conventionally installed.
For built up roofing the gravel was generally 25 5 inches in diameter.
The single ply membrane and other roof components including thermal insulation are loose laid.
A loose ballasted roof where you have 1 to 2 inches of gravel is more on the order of 12 psf.
The gravel used in built up roofing what the roofing contractors were used to was not the same as that used in a ballasted roof.
The weight provided by the gravel is used to anchor down the roof materials therefore using far fewer fasteners to hold the materials to the decking.
None asphalt roll roofing.
The use of timber decking can also be considered as a ballasted application but due to its general lack of sufficient actual dead weight to resist.
I ve had the same questions i think that the 6 psf range given in many tables is for a multi ply roofing with gravel that is impregnated into the top layer.
On the other hand ballast roofing might be the right choice for your commercial property if you live somewhere with a ready source of ballast rocks gravel of the appropriate size and you prefer the aesthetic look and texture of the larger stones.
The weight of roofing constructions above the truss rafter may be estimated with the calculator below.
Drawbacks of a ballasted roof system.
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When it comes to estimating the weight of an existing roof field verification of the in place construction is necessary.
Extremely difficult to find a leak in this system since the membrane is well hidden.
The gravel can be applied in far less time than using a specially designed screw and plate fastening pattern.
The buildup is ballasted with a gravel layer of at least 50 mm and 80 kg m 2.
