While most residential roof designs are severely slanted and topped with shingle or tile of varying types, some roofs are flat, with only a mild incline that allows water to run off. Older low slope systems often used simply tar with embedded rock, but these sometimes allowed water to pool and designers eventually learned that seamless sheets of solid material is preferable. Sometimes flat roofs are covered in sheets of metal such as tin or copper, but this is very costly. The need for low cost yet effective flat roofing materials has lead to the development of modern materials. Today, there are three basic types of systems most commonly used, these are: BUR, modified bitumen, and single ply polymers.
Asphalt BUR
Asphalt BUR is possibly the most common type of flat roofing material in use today. Similar to tar and gravel of the past, BUR consists of layered asphalt with gravel on top. However, this modern system uses multiple layers of asphalt, with reinforcing ply between, creating a build-up of waterproof layers which is very effective. Gravel is then put on top, usually white gravel, which helps to offset heat.
Modified Bitumen
Also popular is modified bitumen, which is also a tar product, but here the tar has been mixed with additives to help it age better and then applied to sheets of polyester or fiberglass. Modified bitumen comes in large roles which are applied by either heating the bottom layer of the material with a torch or simply painting on an adhesive, then rolling the roofing material out onto the roof. Seems, which are kept to a minimum, are overlapped to prevent water penetration.
Single Ply
Single Ply materials are those where a large, thin sheet of materials is created, then layered on the roof and attached by adhesive or mechanical fasteners. There are three popular single ply roofing materials, EPDM, TPO and PVC.
Ethylene Propylene Diene Monomer (EPDM) is a very common single roofing material, which is made mostly of rubber. This material is inexpensive and easy to apply. Historically, EPDM had some problem with moisture penetration due to seams not adhering to each other and condensation in air conditioned buildings. However, new seeming processes and the use of vapor barriers have mitigated these issues. Thermoplastic Polyolefin (TPO), is another type of single ply which is up to four times stronger than EPDM, thus considered more environmentally friendly and economical. PVC, a type of vinyl, is made of petroleum and salt which is then chemically transformed into a thin sheet. Multiple sheets are adhered together through heat, creating water tight seems. As you can see, there are many types of Miami Roofing products for low sloped roofs, feel free to give us a ring at Roof-Tech anytime if you’d like to learn more about the products discussed in this entry.