Replacement of Mastic Patch with 2 Ply Membrane

Case Study

Mid-process in removing the mastic patch around the drain bowl. I’ve already “spudded” the roof around the drain’s sump box (scraped off the topical gravel) which provides me with a smooth and relatively clean surface on which to apply the new patches.

Substrate prepped and ready for rebuilding the drain detail.

We installed a new lead sheet into the drain bowl and then torched some base membrane down to tie (join) the lead into the rest of the roof. Leads are commonly used on mechanical drains and fail after time.

Base ply completed with patch “buttered” on all sides. This “buttering” ensures a good watertight bond to a less then ideal substrate – the old roof.

Patch completed with a 2nd ply of granular membrane for UV protection. note the granular membrane comes out farther onto the roof then the first base ply did. We now have a two ply patch with two “bonds”, “tie-ins” or “barriers” that the water would have to penetrate before a leak reoccured.

Customer: David Beale
Project Completed: April 2014
Type of Roof: Tar and gravel
Materials: 2 ply granular membrane
Location: 315 Powell Street, Vancouver, BC

On this site, an old mastic patch needed to be removed around the drain, and we had to patch the whole sump box area.There was a leak showing up in a closet of an SRO (Single Room Occupancy) building. The building is run by an organization that serves the less fortunate in our society: recovering addicts, abuse victims etc.

I was hired by a contractor who was doing remodeling and minor repairs to the building. They had opened up the drywall ceiling to expose the leak area. We saw that the underside of the mechanical drain was where the leak/drip originated from. Up on the roof we noted that the drain had been modified from it’s original condition and several years ago a previous contractor had applied a cold process mastic patch around the drain area.

These mastic patches commonly dry, crack and fail over time. I quoted on removal of the old patch and repair with new and more permanent torch on membranes.