Porches, dormers, additions, and modern homes often have flat or low-slope sections that asphalt shingles cannot protect. We install systems built to pond water without leaking.
Shingles need slope to shed water, so the flat and low-slope parts of a Bellingham home, the porch roof, the dormer, the addition off the back of a 1950s Roosevelt ranch, need a different system. We install single-ply TPO membrane or torch-down (modified bitumen), both built to handle standing water through our long wet season without leaking.
Low-slope failures almost always start at the transitions and the edges: where the flat section meets the main roof, where it ties into a wall, and at the drains and scuppers. We weld or torch the seams properly, flash the transitions, and detail the edge metal so water has nowhere to sneak in. Done right, a flat section is just as dependable as the pitched roof above it.
What it actually costs.
Flat & low-slope roofing $8,000 to $20,000
Section sizeSquare footage of the flat or low-slope area
SystemTPO membrane vs. torch-down
TransitionsHow it ties into the main roof and walls
DrainageDrains, scuppers, and edge metal
Our process.
Inspect and quote
We assess the low-slope section, the transitions, and the drainage, then quote the system.
Tear off and prep
Old membrane or roofing off, decking checked and repaired, surface prepped.
Membrane or torch-down
TPO welded or torch-down applied, with full attention to the seams.
Flash and detail edges
Transitions flashed, edge metal and drains detailed so water sheds clean.
Why hire us for flat & low-slope roofing.
TPO membrane or torch-down built to pond water
Seams welded or torched properly, not just glued
Transitions and edge metal detailed where leaks start
Pairs cleanly with the shingle or metal main roof
Workmanship warranty plus the manufacturer warranty
Frequently asked questions.
How much does a flat roof cost in Bellingham?
A flat or low-slope roof section in Bellingham runs $8,000 to $20,000 in 2026 depending on the square footage, the system, and the transitions and drainage. A small porch roof is at the low end; a large addition or a full low-slope main roof runs higher. We quote it after we inspect.
TPO or torch-down, which is better?
Both work well here when installed right. TPO is a single-ply membrane that is light, reflective, and welds into a continuous surface. Torch-down (modified bitumen) is a tough, multi-layer system that holds up well to foot traffic and ponding. We will recommend the one that fits your section, your budget, and how the area gets used.
Why does my flat roof keep leaking?
Low-slope roofs almost always leak at the transitions and edges, not the open field: where the flat part meets the main roof or a wall, and at the drains and scuppers. A patch over the field will not hold if the real problem is the flashing. We fix the cause at the transitions so it actually stops.
Ready for a free flat & low-slope roofing quote?
Tell us about your roof and we'll reply within 15 minutes during business hours.
Every neighborhood we serve has its own roofs: historic Victorians in Fairhaven, mossy shaded slopes on South Hill, lake cabins at Silver Beach. Pick your area for local notes: