Direct answer
Torch-applied waterproofing means welding polymer-modified bitumen membrane to a primed deck with a propane torch until side and end laps show a continuous bleed line without cold spots or fish mouths. On Pakistani commercial roofs and podiums, PetroGrip APP is the usual exposed cap sheet; PetroGrip SBS is the usual torch ply for basements, rafts, and movement-prone planes. Petroseal Enterprises manufactures both in Lahore.
Success depends on substrate dryness, correct primer, lap probe before cover-up, and protection before backfill or traffic—not on brand slogans. Specify modifier, thickness, surfacing, overlap, and protection in the BOQ so bids compare like for like.
Deck type → PetroGrip starting point
| Deck / plane | Modifier | Typical thickness | Notes |
|---|---|---|---|
| Exposed flat roof (Punjab / Sindh sun) | APP | 4mm cap (3mm on small decks) | Aluminum or granular surfacing |
| Protected ply under screed / insulation | APP or SBS | 2–3mm plain | Not left UV-exposed |
| Basement wall / raft | SBS | 4mm primary; 3mm second ply if double-layer | Protection board before backfill |
| Podium / split slab | SBS | 3–4mm | Detail planters and movement joints |
| Flame-restricted detail / wet pod | — | 1.5–2mm self-adhesive | PetroSelfGrip; lap to torch field |
What torch-applied waterproofing means on site
The compound must flow at the seam so reinforcement stays encapsulated. Inspectors look for bleed at side and end laps, staggered T-junctions, and reinforced patches at penetrations—not mastic over a cold lap.
Large factory, mall, university, and hospital decks still use torch crews for field sheets because of seam strength and local applicator experience. PetroSelfGrip covers bathrooms, lift pits, and hospital wards where open flame is restricted.
Primer, dust, and deck preparation
Bituminous primer on concrete must match the membrane system. Sweep and blow down before primer; dust is a common bond failure. Allow primer to reach the tack window on the can before unrolling the first sheet. Detail cant strips and reglets before membrane starts.
Side laps should be staggered so T-junctions do not stack. Walk the grid while welds are open—not after screed or insulation buries them.
APP versus SBS on the same torch crew
The same torch and primer discipline applies to both modifiers; design intent differs. APP PetroGrip is stiffer at ambient temperature and suited to heat-stable caps. SBS PetroGrip is more flexible—preferred at basement walls, split slabs, and movement joints. Overheating SBS thins compound at the lap; heat until bleed appears, then roll without scorching reinforcement.
For climate-driven selection and 3mm vs 4mm guidance, use the dedicated APP vs SBS and thickness guides. Domestic alternatives such as Roofline rolls follow the same APP/SBS logic—Petroseal PetroGrip adds Lahore batch marking and published system pages.
- 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.
- Photograph roll markings and lap bleeds before protection or screed.
Petroseal supports contractors with datasheets, on-site guidance where scheduled, and Made-in-Pakistan traceability from the Lahore plant. Torch-applied waterproofing is unforgiving of skipped primer, wet decks, and rushed laps.
Pairing torch membrane with insulation and coatings
Many roofs stack Green Insulation XPS or PUF under a PetroGrip cap—thermal layer first, separation sheet if specified, then torch membrane. Polyurethane coatings at drains and curbs can complement membrane on complex slabs; document the interface.
Specify the full build-up: insulation, modifier, thickness, surfacing, and protection. Torch-applied PetroGrip remains the workhorse for exposed waterproofing Petroseal manufactures in Pakistan.
From tender documents to handover
Tenders that only say torch membrane without APP/SBS, thickness, or surfacing force guesswork. Name PetroGrip products, primer, overlap, and protection board in the BOQ. At handover: as-built lap sketches at drains and equipment stands, primer batch records, and membrane roll photos on deck.
Contact Petroseal at 0321 8489737 or petrosealenterprises.com for submittals. Cross-check /systems/app-waterproofing and /systems/sbs-waterproofing for build-up context.