December 11, 2017

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.

Read the full abstract paper TorchOn and SelfAdhesive Asphaltic Membranes._