Vancouver, WA torch-down roofing for flat roofs and decks

Torch-down roofing is modified bitumen, an asphalt-based sheet reinforced with polyester or fiberglass, that is melted onto the roof with a propane torch. As the underside melts, it fuses to the layer below and to itself at the laps, creating a thick, tough membrane. It handles foot traffic better than most single-ply sheets and is common on older flat roofs, roof decks and small porch roofs in the region.

Our crews install torch-down as a two-ply system: a base sheet followed by a granulated cap sheet. We also repair existing torch-down roofs by heating and re-fusing lifted laps or adding a patch ply. Because the work involves open flame on a building, our roofers follow a set safety routine every time, and we decline to torch near materials that could catch.

How a two-ply torch-down roof is built

A torch-down roof starts with a clean, dry deck and, on most homes, a layer of cover board or insulation fastened down first. The base sheet goes on next, either torched or mechanically fastened, depending on what lies below. The cap sheet follows, with its laps offset from the base sheet laps so no seam lines up. Each lap gets a visible bead of melted bitumen squeezing out, which is how our roofers confirm a full bond.

Edges and walls get special care. The cap sheet runs up walls onto a cant strip so it never bends at a sharp right angle, then gets covered by metal counterflashing. Drains are set in a lead or metal flange and flashed in layers. Granules on the cap sheet protect the asphalt from sunlight, so we keep loose granules handy to broadcast into any fresh bleed-out at the laps, so no black asphalt is left exposed.

Fire safety on every torch job

Torching is safe when it is done with discipline, and dangerous when it is rushed. Our crews treat fire safety as part of the job, not as an add-on. Near wood siding, skylight curbs and eaves where heat could reach hidden material, we switch to self-adhered membrane rather than risk it. That rule costs a little more in material but removes the main fire risk on residential work. Safety steps are never skipped to save time.

• Charged extinguishers on the roof at all times
• No torching directly against wood or into gaps
• Self-adhered sheet near siding and eaves
• Fire watch for an hour after the last torch
• Infrared check of edges before leaving
• Propane cylinders stored and secured properly

Repairing an existing torch-down roof

Torch-down holds up well, but it does age. Granules wear off in foot paths and in spots where water ponds, exposing the black asphalt to sun, which then dries and cracks. Laps lift where the original installer did not get full bleed-out. Blisters appear where moisture was trapped during installation. Most of these can be repaired by cutting out the damaged area, priming the surface and fusing a patch over it.

We check whether the old roof can take a new cap ply over the top. When the base layers are firmly fused and dry, adding a fresh cap sheet can extend the roof's life at a lower cost than a full tear-off. If moisture probes show wet insulation or the roof already has too many layers, tear-off is the only sound choice. We show you the probe readings that support either decision.

Torch-down compared with single-ply

Owners often ask whether to choose torch-down or a single-ply membrane like TPO. Torch-down is thicker and stands up better to foot traffic, dropped tools and furniture on a deck. TPO is lighter, reflects more sun and goes on without flame. For a deck or a roof that people will walk on, we usually favor torch-down or a deck-grade PVC. For a roof that no one walks on, single-ply is often the simpler and lower-cost choice.