Elastomeric Membrane Installation on a Laval Commercial Building

This mixed-use building in Laval had a flat roof with an aging modified bitumen membrane that had been patched repeatedly over the years. Ponding water in several areas had accelerated membrane deterioration, and the building owner was dealing with recurring leaks into the commercial spaces below. We removed the existing membrane layers down to the roof deck and discovered areas where the structural decking had deteriorated from prolonged water exposure. After replacing the damaged sections, we installed tapered rigid insulation boards to correct the drainage issues that had caused ponding. The tapered system directs water toward existing roof drains, eliminating the low spots that had plagued the previous installation. A two-layer SBS elastomeric membrane system was then torch-applied over the insulation. The base sheet was mechanically fastened and torch-welded, followed by the cap sheet with a granulated surface for UV protection. All penetrations including HVAC units, plumbing vents, and electrical conduits were carefully detailed with reinforced membrane boots and sealant. Parapet walls were stripped and re-flashed with new membrane extending up the wall face and capped with metal coping. New scupper details were installed at overflow locations for secondary drainage protection. The completed roof provides reliable waterproofing and improved thermal performance for the building.