What torch-applied waterproofing means on site
Torch-applied waterproofing uses a propane torch to heat the underside of a polymer-modified bitumen roll and the substrate primer so laps fuse into a continuous monolithic layer. PetroGrip APP and SBS membranes from Petroseal Enterprises are designed for this method: the compound flows at the seam, the reinforcement is encapsulated, and the finished lap should show a bleed line without cold spots or fish mouths.
On large exposed concrete roofs—factories, universities, hospitals, and commercial buildings—torch work remains the dominant cap-sheet installation. PetroSelfGrip solves flame-restricted zones, but the main field area on a textile roof or hypermarket deck is still torch-applied because of speed, seam strength, and decades of local applicator experience.
Primer, dust, and deck preparation
Primer selection must match the deck: bituminous primer on concrete, with cant strips and reglets detailed before the first roll is unrolled. Dust is the silent failure mode— a gritty deck prevents primer bond; applicators should sweep and blow down before primer, then allow the primer to tack within the window printed on the can.
Side laps are typically staggered so T-junctions do not stack; inspectors should walk the grid while work is open, not after screed or insulation buries welds.
APP versus SBS on the same torch crew
The same torch and primer discipline applies to both modifiers, but the design intent differs. APP PetroGrip rolls are stiffer at ambient temperature and suited to heat-stable cap sheets. SBS PetroGrip rolls are more flexible—preferred at basement walls, split slabs, and movement joints.
A common error is torching SBS too aggressively and thinning the compound at the lap; trained crews heat the seam until bleed appears, then press with a roller without scorching the reinforcement.
- 2mm and 2.5mm in protected build-ups
- 3mm and 4mm at the primary waterproofing or cap sheet line
- Match thickness and surfacing to the consultant detail—not whichever roll fits the truck
Quality control every owner should insist on
- Require primer type and coverage rate in the method statement.
- Mark start and end of each shift on the deck for traceability.
- Probe side laps and end laps; reinforce T-junctions per detail.
- Use prefabricated boots or reinforced patches at penetrations—not mastic over a cold lap.
Petroseal supports contractors with datasheets, on-site guidance where scheduled, and Made-in-Pakistan traceability from our Lahore plant. Torch-applied waterproofing is unforgiving of skipped primer, wet decks, and rushed laps.
Pairing torch membrane with insulation and coatings
Many roofs now stack Green Insulation XPS or PUF boards under a PetroGrip cap sheet—thermal layer first, separation sheet if specified, then torch membrane. Polyurethane chemical coatings at drains and curbs complement membrane on complex slabs.
Specify the full build-up: insulation, membrane modifier, thickness, surfacing, and protection. Torch-applied PetroGrip remains the workhorse for exposed waterproofing—and Petroseal manufactures the rolls you weld on those decks.
From tender documents to handover
Tender drawings that only say torch membrane without naming APP, SBS, thickness, or surfacing force applicators to guess. Insert PetroGrip product names, primer type, overlap width, and protection board into the BOQ so bids compare like for like.
At handover, deliver as-built lap sketches for drains and equipment stands, primer batch records, and membrane roll markings photographed on the deck. Contact Petroseal at 0321 8489737 or petrosealenterprises.com for scheduling and submittals.