SBS Roofing

Standard asphalt is a thermoplastic. It softens when hot and goes brittle when cold. On a Calgary roof that cycles from above 60 degrees Celsius at the membrane surface in July to below minus 30 in January, unmodified asphalt cracks.

Adding SBS polymer at roughly 12 to 15 percent by weight turns the asphalt into an elastomer. Two properties change and both of them matter here:

Low-temperature flexibility. SBS membranes stay flexible well below freezing. The industry test is cold-flex or cold-bend temperature, and SBS products are commonly rated to around minus 30 degrees Celsius. APP-modified membranes, the other common polymer, are stiffer in cold and better suited to hot climates.

Elastic recovery. SBS returns to shape after being stretched. A roof deck that moves seasonally does not tear the membrane, it flexes it.

For a city with chinooks, that combination is the reason SBS won the Alberta market rather than APP.

Torch-applied. A propane torch melts the underside of the membrane as it is rolled out, and the molten asphalt bonds to the substrate. It produces the strongest bond and it works in cold weather. It also involves open flame on a roof, which requires fire watch procedure and rules it out over some substrates.

Self-adhered. A release film is peeled and the membrane sticks. No flame. It needs surface temperatures above the manufacturer's minimum, so its Calgary installation window is narrower.

Note that torch-applied SBS is not the same as hot tar. Hot tar, or built-up roofing, means heating asphalt in a kettle and mopping it in place. Our insured scope of operations is roofing and repair excluding hot tar. Torch-applied SBS falls inside that scope; built-up kettle work does not.

SBS membranes fail in four recognisable ways.

Lap separation. Side or end laps lose adhesion and lift. Most common where the original torch pass was rushed or the substrate was damp.

Granule loss. The cap sheet loses its mineral surfacing and the asphalt below it is exposed to ultraviolet light. Once the asphalt is bare, the clock speeds up.

Blistering. Trapped air or moisture between plies expands under heat. A split blister is a leak.

Alligatoring. Surface crazing in a pattern of interlocking cracks, indicating oxidation of the asphalt.

Draft A correctly installed two-ply SBS system should give 20 to 30 years in Calgary. The variable is not the membrane, it is drainage and maintenance: a roof that clears water within 48 hours and gets its drains cleared twice a year will reach the top of that band, and one that ponds all winter will not reach the bottom of it.

IKO Torchflex is the two-ply line most commonly specified on Alberta roofs, with Soprema and Bakor also widely used here. The base sheet and cap sheet have to come from the same system; mixing manufacturers across the two plies voids the warranty on both.