If your planning on replacing your commercial flat roof there are four main types of commercial flat roofing.

Built-Up Roof
BUR is also a very attractive and aesthetically pleasing roof as the top coat is typically gravel and looks very nice. They are installed using several layers of a special type of roofing felt that has been asphalt impregnated and embedded in bitumen applied with a hot mop. The hot asphalt with the bitumen soaked roof felt and creates a roof membrane. The roof asphalt tar layering is repeated in overlapping layers until the assembly is two to fours plies in thickness. A wear surface of finely crushed stone granules is usually applied to the top layer of hot tar to protect the built up roof from UV light and weather.

Modified Bitumen

A modified bitumen roof is usually only made of of two layers, a base sheet and a cap sheet. A modified bitumen flat roof uses asphalt and polymer with a wear surface can be gravel in bitumen. Application is peel-and-stick as the membrane is unrolled. This is one of the more environmentally friendly flat roof options as it reflects the sun and therefore cuts back on energy costs. However, this system is not very scuff or tear-resistant and cannot resist much foot traffic once applied.

Single Ply Membrane

Single Ply membrane is one of the top flat roof options because it is easy to install and lacks water permeability. They are lightweight, flexible, resistant to UV and micro organisms, handle extreme weather and temperature changes, fire resistant and self extinguishing, show good chemical resistance, and can be very environmentally friendly. When it is rolled out, these seams must be taped or glued together. While this may resist water for a while, it will not hold up for 10-15 years as a seamless roofing system would.

Metal Flat-Seam Roof

Metal flat-seam roofs use sheets of metal, such as copper or stainless steel, joined together by folding adjacent edges over, then under, to make lock seams. The seam is flattened with a mallet and soldered to prevent leaks. On large areas of roof, expansion battens help the roof contract or expand in response to heat and cold without damage.