Flat Roof Repair in Portland, OR
A flat roof is a low-slope roof covered by a continuous membrane. It leaks at seams, drains and edges, and it is repaired by people who work with membranes, not shingles.
What counts as flat roof repair in Portland?
Flat roof repair is work on a low-slope roof: one too shallow for shingles, covered instead by a membrane that is sealed at every seam. Around Portland these are on mid-century houses, on porches, dormers and additions attached to pitched roofs, on garages, and on rowhouses and condos. The membrane is one of three families: TPO or PVC, EPDM, or modified bitumen, which most people call torch-down. The table below sets them side by side.
Typical repairs:
- Seams. Re-welding or patching a lap that has opened.
- Drains and scuppers. Clearing them, and resealing the membrane where it ties into the drain.
- Edge metal and parapet caps. Where wind and movement work the membrane loose.
- Penetrations and curbs. Pipes, vents and skylights, each with its own flashing.
- Blisters and punctures. Cut out and patched if the insulation below is dry.
Why do flat roofs fail?
Almost always water that could not leave. A low-slope roof is built with a slight pitch toward its drains. When a drain clogs with leaves, or the deck settles into a low spot, water stands. Standing water finds seams, and once it is under the membrane it soaks the insulation, which stays wet. A roofer checks for that by walking the roof for soft areas and, on larger jobs, cutting a small test core.
If water shows up inside, the roof leak page covers what to do first. The stain may be well away from the entry point, as it is on a pitched roof.
Repair or replace?
Patch a sound membrane; replace a tired one. When a flat roof is replaced, the bid should say whether the old membrane and wet insulation come off, how the roof will drain afterward, and which membrane goes on. Published replacement figures on the cost page are for pitched roofs, so a roofer’s bid is the number to rely on for low-slope work.
Where a flat section meets a pitched roof, the joint between them is a common leak. That work overlaps with roof repair, and when the whole house is being redone, with roof replacement.
What this typically costs
| Work | Typical range | Basis | Source |
|---|---|---|---|
| Roof replacement, OregonState average modeled from material cost data on a moderately pitched roof. Not specific to Portland. | $5,639 - $18,173 | per roof, Oregon statewide range | This Old House, Roof Replacement Cost in Oregon (thisoldhouse.com), updated June 8, 2026checked September 30, 2026 |
| Roof replacement, nationalCustomer-reported project costs across the country, all materials and roof sizes. | $5,902 - $13,377 | per roof, typical national range | HomeAdvisor, How Much Does a Roof Replacement Cost (homeadvisor.com), updated June 17, 2026checked September 30, 2026 |
| Tear-off and disposalThe removal portion of a replacement. More layers and steeper pitch push it up. | $1,500 - $4,500 | per roof, national, permit not included | HomeAdvisor, How Much Does a Roof Replacement Cost (homeadvisor.com), updated June 17, 2026checked September 30, 2026 |
| Asphalt shingle replacement, Pacific regionOne standard project priced by region, a full tear-off on a large house. It sits far above the averages because of that fixed scope. | $36,391 | per job, regional average for a fixed project specification | JLC / Zonda, 2025 Cost vs. Value Report, Pacific region (jlconline.com)checked September 30, 2026 |
| Metal roof replacement, Pacific regionSame report and method as the asphalt row, with metal in place of shingles. | $62,152 | per job, regional average for a fixed project specification | JLC / Zonda, 2025 Cost vs. Value Report, Pacific region (jlconline.com)checked September 30, 2026 |
| Roof repairCustomer-reported costs for repairs of all kinds. | $395 - $1,967 | per repair, typical national range | HomeAdvisor, How Much Does Roof Repair Cost (homeadvisor.com), updated June 19, 2026checked September 30, 2026 |
| Roof leak repair | $360 - $1,550 | per repair, national | HomeAdvisor, How Much Does Roof Repair Cost (homeadvisor.com), updated June 19, 2026checked September 30, 2026 |
| Flashing repair | $200 - $500 | per repair, national | HomeAdvisor, How Much Does Roof Repair Cost (homeadvisor.com), updated June 19, 2026checked September 30, 2026 |
Prices on this page are general ranges gathered from published sources, not a quote. What a job actually costs depends on the specifics of the job and who does the work. Only a quote from a qualified contractor who has seen the job is a real price. Last reviewed September 30, 2026.
How it works
Describe the roof
Enter the ZIP code, pick the kind of work, and say what you are seeing: a leak, wind damage, an old roof, or a quote you want to compare.
Your request goes to a roofer
We pass it to an independent, CCB-licensed roofing contractor who works in your part of the metro. We do no roofing ourselves.
The roofer inspects and bids
The contractor contacts you directly, looks at the roof and gives you a written bid with their own price and scope.
You look up the license and decide
Check the CCB number on the bid, compare it with any other bids you have, and hire them or not. There is no obligation.
Signs it is time to call someone
Water still standing on a flat roof days after the rain stops
A low-slope roof is built to drain, not to hold water. Standing water means a blocked drain or scupper, a low spot in the deck, or insulation that has compressed. It loads the structure and finds any weak seam in the membrane.
A ceiling stain, a drip, or wet insulation in the attic
Water rarely comes through the middle of a sound shingle. Most leaks start where the roof is interrupted: a plumbing vent, a chimney, a skylight, a valley or a wall. The stain inside is often several feet from where the water gets in, because it runs along the deck or a rafter first.
Which flat roof membrane?
| Attribute | TPO or PVC | EPDM | Modified bitumen |
|---|---|---|---|
| What it is | A single-ply plastic sheet | A single-ply rubber sheet | Asphalt-based sheets in one or more plies |
| How seams are made | Welded together with hot air | Joined with seam tape or adhesive | Torch-applied or self-adhered laps |
| Usual color | White or light grey | Black | Granule surface in several colors |
| Also called | Single-ply | Rubber roof | Torch-down |
Request a Roofing Quote
Tell us about your roof and we pass your request to a local, CCB-licensed roofing contractor who can quote the work.
Common questions
Where do flat roofs leak most?
At seams, around drains and scuppers, at the edge metal, and where the membrane turns up a wall or wraps a pipe or skylight. The open field of a membrane rarely fails first.
Is standing water on a flat roof a problem?
Water that is still there days after rain is. It means a drain or scupper is blocked or the roof has a low spot, and standing water works on every seam it covers. Clearing the drain is the first step; a low spot needs a roofer.
Can a flat roof be repaired, or does it need replacing?
A sound membrane with one open seam or a failed flashing can be patched with the same kind of material. A membrane that is brittle, shrinking away from the edges or wet underneath across a wide area is a replacement.
Can shingles go on a flat roof?
No. Shingles shed water by overlapping on a slope and are not made for low-slope roofs. A low-slope roof needs a continuous membrane.
Is TPO roofing available for houses in Portland?
Yes. TPO is common on commercial buildings and is also used on residential low-slope roofs. Say on the request form that the roof is flat so the request reaches a roofer who does membrane work.
Request a Roofing Quote
Tell us about your roof and we pass your request to a local, CCB-licensed roofing contractor who can quote the work.