Modern Single-ply roofing systems use only one layer of membrane material versus multiple layers as in BUR systems.
Single-ply roofing must possess 3 attributes:
- Provide Waterproofing- which is provided by the membrane. Membranes are between 36-120 mils thickness. Common sizes are 45, 60, and 90 mils. Mil stands for millimeter which is 1 mil is,001 of an inch. 45 mils are approximately the thickness of a dime and 60 mils are approximately the thickness of a nickel.
- Strength- which is usually provided enforcement “scrim” embedded in the membrane. This scrim increases membrane strength, resists punctures, and cracking and allows for expansion without membrane denaturing.
- Surface Protection- which is either provided by a coating that is prefabricated by the manufacturer in the single-ply membrane as a coating or by ballasts installed by the roofer. Surface protection is important to the longevity of the overall roofing system. TPO, PVC, modified bitumen and some EPDM has a coating fabricated in the membrane to reflect ultraviolet rays. Not only does it provide protection but it also provides energy-saving and heat-reflective properties to the entire building envelop. Ballasted systems use stones to hold down the EPDM membrane and providing the same properties as stated above. Ballasted systems give great protection against hail but can be difficult to service because the rocks have to be removed to investigate problems. Moreover, just walking across the ballasts (rocks) can cause penetrations over time as rocks can break and become sharp.
Advantages of single-ply roofing
- Single-ply roofing is lighter than BUR and may be laid over an existing roof system which decreases the cost by avoiding having to remove the entire old roofing system. [If allowed by manufacturer or code].
- Less material than BUR equals lower costs.
- Expands and contracts better than BUR.
- Better adaptability to aesthetic architect design.
Single-Ply Roofing Example (Mechanically attached)