Glossary


Alligatoring is the cracking of the surfacing bitumen on a bituminous roof or coating on a SPF roof, producing a pattern of cracks similar to an alligator’s hide; the cracks may not extend completely through the surfacing bitumen or coating.

Blistering of Roofing Membranes Blisters are raised areas of a roofing membrane where pockets of air and moisture are present. It usually occurs on hot and sunny days.

Roof Ponding is the retention of water on a low-slope or flat roof caused by a deflection of the roof’s underlying structural components. Ponding water on a roof causes leaks, algae and fungi growth. If left unattended, roof ponds can lead to the collapse of a roof.The size of roof ponds increases over time because the weight of the water causes additional deflection of the structural membranes underneath. Eventually, the structure will not be able to carry the increased load and the roof collapses.

Thermoplastic Polyolefin (TPO) roofs are thermoplastic membrane roofing assemblies formed with reinforced and unreinforced thermoplastic membranes. They include ballasted, fully adhered, and mechanically attached installations.

Thermoplastic Polyolefin (TPO) comes in large rolls and must be glued or mechanically fastened to a roof, and sealed at all seams. This is in contrast to other roofing, typically known as Built-Up Roofs, which utilize hot asphalt and other hazardous components as the roof is constructed in place. The three major categories of single-ply membranes are Thermosets, Thermoplastics and Modified Bitumens.

Crazing is the development of a multitude of very fine cracks on single ply membranes such as TPO’s and PVC’s. It is similar to alligatoring. Crazing on single ply membranes occur on the top layer above the reinforcing mesh. If deterioration continues, the craze can become a crack which results in roof failure. Widespread crazing allows water to penetrate the membrane causing roof leaks which can be difficult to isolate and repair.

Chlorinated Polyethylene (CPE) is a thermoplastic material, used for single-ply roof membranes, composed of high molecular weight polyethylene that has been chlorinated with a process that yields a flexible rubber-like material.

Ethylene Propylene Diene Monomer (EPDM) roofs are roofing materials formed with vulcanized and non-vulcanized elastomeric membranes. They include ballasted, fully-adhered, and mechanically attached installations.

Acrylic Elastomeric Coatings The most widely used roof coating. They can be used on all properly sloped roofing surfaces that do not pond water.

Butyl Elastomeric Coatings The preferred roof coating for flat roofs such as asphalt built up (BUR), modified bitumen (APP and SBS). Highly resistant to ponding water.

Silicone Elastomeric Coatings A popular protective coating for polyurethane foam. Use on new installations or to recoat an existing silicone coated roof.









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