Built-up roofing is the most common type of low-slope roof you will come across. It is composed of several layers of bitumen with a layer of gravel on top to protect the surface from heat, snow, and rain.
More modern installations now come with a layer of rigid insulation, which adds a higher R-Value to the roof making it much more energy-efficient than it used to be.
The layers of the built-up roof are called ply-sheets and are usually made from fiberglass or an organic material depending upon the type of installation. They are commonly made in rolls that are 36 inches wide. A bitumen is applied to seal the layers and is usual coal tar, asphalt, or a cold-applied adhesive. The coal-tar or asphalt is heated in a kettle or tanker and is applied using a mop or special applicator.
Asphalt is a petroleum product derived from crude oil, while the coal-tar is derived from the process of distilling coal. A cold-applied adhesive is a solvent-based asphalt and does not need to be heated like the other two products.
The cold-applied product is not dependent upon the weather for proper application and has no toxic fumes, which means it is better for the environment. In the long-term, cold-applied material usually out-performs its hot predecessors.
The most common form of BUR is the asphalt, but there are several more alternatives available that depend on your building’s location, the type of building, and several other factors, including cost. It is best to consult a flat-roof specialist before making a decision as to which roof would best suit your particular situation.
Asphalt degradation is becoming a concern in recent years. Harmful UV rays will oxidize the surface of the asphalt which creates a chalk-like substance. Also, plasticizers leach from the asphalt which causes the layers to become brittle and allows them to lose their waterproof qualities. This also causes the layers to alligator, crack, and becomes loose allowing water to penetrate the layers and eventually leak into the building. Regular maintenance is required for this type of roof.
Pros and Cons of BUR
Pros
• Does an excellent job at waterproofing the roof
• Ultra-violet light does not harm the roof as much as other types of products
• Much more resistant to adverse weather conditions
• Maintenance costs are relatively low
Cons
• Installation is time consuming
• Fumes are hazardous when installing
• Installation cost is high
• Wind and rain may cause damage
The built-up roof is just one of the several options available for your low-sloped roof. What is right for your particular installation varies and is dependent on a number of factors, including cost. Your flat-roofing expert can look at your roof and give you several options, all with varying price levels, which will allow you to make an educated decision for your roof installation.
Contact Essential Flat Roofing for all your roofing needs.