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# Flat roofs, sealed and drained properly

Straight Arrow Roofing & Siding installs, repairs and replaces flat and low-slope roofs on garages, additions, porches, dormers and commercial buildings across Brantford, Hamilton, Halton, Cambridge and Paris, and tracks down flat-roof leaks. Shingles shed water by overlapping and need slope to work, so a flat roof needs a continuous sealed membrane and somewhere for the water to go.

Updated 16 October 2026 by Straight Arrow Roofing & Siding

![A finished single-ply flat roof over a garage with a metal edge](https://straightarrow-dev.pages.dev/assets/img/flat-roof-garage-900.webp)

## What are flat roofs made of?

| System | What it is | Where it fits |
| --- | --- | --- |
| Modified bitumen | Asphalt sheets with a reinforcing mat, laid in two plies and sealed at the seams | Garages, additions and porches on houses |
| Single-ply membrane | One large rubber or plastic sheet (EPDM or TPO) with few seams | Larger flat areas and commercial roofs |
| Built-up roof | Layers of felt and hot asphalt, often finished with gravel | Older commercial buildings, usually repaired or replaced with one of the above |

Which one suits your roof depends on its size, what is on it, how it drains and what the walls around it are made of. We will tell you what we recommend and why.

## Why do flat roofs leak?

- **Ponding**: water that sits after rain finds every weak seam. A flat roof should still have a slight slope to a drain or a scupper.

- **Seams** that were never fully sealed, or have opened up with years of heat and cold.

- **Edges and walls**, where the membrane turns up a wall or over a metal edge.

- **Penetrations**: vents, pipes, skylights and rooftop units each need their own detail.

Leak detection on a flat roof means tracing the water back from where it shows inside. The source can be metres away.

![A finished dark flat roof on a one-storey addition beside a brick house](https://straightarrow-dev.pages.dev/assets/img/flat-roof-addition-800.webp)
A finished dark flat roof on a one-storey addition.

## Can you put a skylight in a flat roof?

Yes, on a raised curb so the glass sits above standing water, with the membrane carried up the curb. See [skylights](https://straightarrow-dev.pages.dev/services/skylights/). In Oakville, the Town lists skylights among work that needs a building permit.[1]

## Where do we do flat roofing?

Across our whole area: [Brantford](https://straightarrow-dev.pages.dev/areas/brantford/), [Paris and the County of Brant](https://straightarrow-dev.pages.dev/areas/paris/), [Hamilton, Ancaster, Dundas and Waterdown](https://straightarrow-dev.pages.dev/areas/hamilton/), [Burlington](https://straightarrow-dev.pages.dev/areas/burlington/), [Oakville](https://straightarrow-dev.pages.dev/areas/oakville/), [Milton](https://straightarrow-dev.pages.dev/areas/milton/), [Cambridge](https://straightarrow-dev.pages.dev/areas/cambridge/).

## What else do we do?

- [Roof replacement](https://straightarrow-dev.pages.dev/services/roof-replacement/) Full tear-off to the deck and a complete new roof system, often in a single day.
- [Roof repair](https://straightarrow-dev.pages.dev/services/roof-repair/) Leaks, lifted or missing shingles, flashing, vents and storm damage.
- [Roof inspections and maintenance](https://straightarrow-dev.pages.dev/services/roof-inspections/) A proper look at the roof and the attic before anyone quotes a price.
- [Metal roofing](https://straightarrow-dev.pages.dev/services/metal-roofing/) Long-life metal roofs and cosmetic metal capping.
- [Skylights](https://straightarrow-dev.pages.dev/services/skylights/) New skylights, replacements in the same opening, and leak repairs.
- [Eavestroughs, soffit and fascia](https://straightarrow-dev.pages.dev/services/eavestroughs/) Eavestroughs and downpipes, cleaning and repairs, soffit and fascia.
- [Siding](https://straightarrow-dev.pages.dev/services/siding/) Vinyl, aluminum, fibre cement and engineered wood siding.

## Sources

1. [Building permit application process](https://www.oakville.ca/town-hall/online-services/planning-construction/building-permit-application-process/), Town of Oakville, read 16 October 2026.

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Source: https://straightarrow-dev.pages.dev/services/flat-roofing/