Adhesion of torch-on and self-adhesive asphaltic membranes over green concrete

Roofing contractors are often asked by general contractors to start roof installation earlier than 28 days, the time typically specified for strength gain measurement after concrete placement in new construction.
Application of membranes to ‘green’ concrete can be problematic, evidence of problems appearing as
blisters and delamination of the membrane after application. Some applications are successful, and some rules of thumb exist in the industry about when application can proceed. The RCABC RoofStar guarantee standards defer the decision to a structural engineer to allow installation earlier than the 28 day cure time, but industry professionals are reluctant to do so because concrete strength time differs from concrete drying time.

The authors carried out this parametric study of membrane installation to quantify effects on membrane adhesion strength related to its installation during the first month after casting of concrete, when initial strength gain and moisture loss are taking place.

The RCABC has concerns that with the new wind uplift requirements coming into effect in both the National and Provincial Building Codes, a premature approval for membrane application could cause the
roof to fail the wind uplift requirement.

 

This post has been originally published by Roofing Contractors Association of BC

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