Sheet and Torch-On Waterproofing

Self-adhered membrane uses factory-applied adhesive activated by pressure and approved primer, reducing open-flame work. Torch-on modified bitumen is heat-welded to the substrate or base sheet and forms fused seams. Substrate, temperature, geometry, fire risk, exposure, overburden, and the consultant's approved assembly determine which system is appropriate.

Common self-adhered rubberized asphalt foundation sheets are about 1.5 mm thick, while torch-applied modified-bitumen sheets are often around 3 to 4 mm per ply. Multi-ply assemblies add layers. Thickness is only one attribute. Reinforcement, laps, puncture resistance, low-temperature flexibility, bond, and protection are also required.

Lap width is product and orientation specific. Some Canadian self-adhered sheets use roughly 65 mm side and end laps, while modified-bitumen end laps can be wider. Harrowgate marks the required overlap, staggers ends, rolls or fuses every seam, and follows the approved system instead of applying one generic lap dimension.

Only after the project team reviews combustible construction, air intakes, access, fire detection, permits, monitoring, and site hot-work restrictions. Some locations require a self-adhered or cold-applied alternative. Where torch work is approved, Harrowgate uses controlled staging, protection, trained application, fire watch, and final area checks.

Applicators visually review bond and continuous bitumen or adhesive contact, roll or tool laps, and probe cooled seams where appropriate. T-joints, corners, patches, and end laps receive focused inspection. Flood or electronic integrity testing can be added where compatible. Defects are cut back or patched onto clean sound membrane.

Ordinary field sheet cannot be stretched flat across a joint expected to move. The assembly requires a designed loop, bellows, reinforced flexible transition, joint cover, or manufactured system that connects to the waterproofing on both sides. Harrowgate installs the engineered detail and keeps the joint mechanically independent from the field membrane.

Provide plans, sheet and primer specification, ply count, substrate, lap and flashing details, cracks and joints, drains, penetrations, upper terminations, testing, protection, drainage, overburden, winter conditions, hot-work restrictions, and phasing. Harrowgate measures field rolls and detail sheets separately and includes access, inspection, and protection.