A Curb-Mounted VELUX Skylight on a Barrington Modified-Bitumen Flat Roof

Putting a skylight on a flat roof sounds like asking for a leak — and done wrong, it is. This Barrington project shows how it is done right: a curb-mounted VELUX unit rising above a new self-adhered modified-bitumen membrane, flashed so that water is turned away from the opening on every side. The home had lived with an interior ceiling stain from the old assembly, and the rebuild was designed to make sure that history did not repeat. Pinnacle roofs go on fast — often as a one-day roof replacement — and flexible financing keeps a project like this within reach, with plans as low as 0% interest for 18 months.

A curb-mounted VELUX skylight was installed above a new SA modified-bitumen membrane on a low-slope Barrington roof, with the curb built up and the membrane flashed up its sides to keep the opening watertight. This project is in Barrington, Rhode Island using SA Modified-Bitumen membrane.

Scope of Work

The old low-slope roof came off down to a sound substrate — the only honest starting point, because a membrane laid over wet or failed material simply traps the problem underneath. With the deck dry and solid, the crew installed a self-adhered SA modified-bitumen system: reinforced asphalt plies rolled and bonded into one continuous, fully-adhered sheet with no exposed fasteners for water to find. The skylight is the detail that makes or breaks a roof like this, so it was built as a curb, not a hole: a raised wooden curb was set and squared above the roof plane, and the modified-bitumen membrane was carried up and over the curb sides so the waterproofing turns vertical well above where water ever sits. The VELUX unit was then set onto that curb with its engineered flashing, and the perimeter edge metal was installed and sealed so the roof’s edges — where low-slope roofs leak first — are locked down. The result is a skylight that sits above the water plane on a membrane that has nowhere to leak.

What We Installed (And Why)

A flat, or low-slope, roof is a different animal from a shingled one, and the two products here reflect that. The field is a self-adhered modified-bitumen membrane — the proven low-slope system for a roof where water drains slowly and sometimes ponds. Multiple reinforced plies bond into a single monolithic sheet that flexes with the building through Rhode Island’s temperature swings and carries no exposed nail heads to back out and leak. The skylight is a VELUX unit set on a curb, and the curb is the whole point. On a pitched roof a skylight can be deck-mounted low to the shingles because gravity pulls water away quickly; on a low-slope roof the unit must be lifted on a curb so its glass and frame sit well above the water plane, with the membrane flashed up the curb sides and the VELUX flashing sealing the top. VELUX backs its units as No Leak Skylights because that engineered flashing does the waterproofing, and on a curb-mounted installation the membrane-up-the-curb detail adds a second line of defense below it. The glass is a sealed, low-E insulated unit that brings daylight deep into a space a flat roof would otherwise leave dark — a real gain in a room with no pitched ceiling to place a window in. Together the membrane and the curb-mounted glass turn a leak-prone spot into the brightest, driest part of the roof.

Project Photo Gallery

The curb-mounted VELUX skylight rising above the new membrane

The Barrington home after the roof and skylight rebuild

The fully-adhered modified-bitumen membrane that waterproofs the low-slope roof

Good To Know: Can you put a skylight on a flat roof without it leaking?

Yes, but only if the skylight is curb-mounted and the roof around it is a true membrane, not shingles. The problem with skylights on low-slope roofs is that water drains slowly and can pond, so anything sitting flush with the roof is asking to be submerged. The solution is to build a raised curb — a squared wooden frame that lifts the skylight several inches above the roof plane — and then carry the waterproofing membrane up the sides of that curb before the VELUX unit and its engineered flashing go on top. Now the glass and its seals sit well above where water ever reaches, and the membrane creates a continuous waterproof barrier that turns vertical at the curb. The old failures that leave ceiling stains almost always trace back to a skylight mounted flush and sealed with caulk on a roof that holds water. Lift it on a curb, flash it into a proper membrane, and a flat-roof skylight becomes one of the most reliable parts of the roof.

Why This Approach Works

On a low-slope roof, leaks start at edges, penetrations, and anything that interrupts the membrane — which is exactly what a skylight is. Building the opening as a raised curb and running the membrane up its sides means the interruption is lifted above the water plane and wrapped into the waterproofing, so the very feature that seems risky is detailed to be as dry as the field around it.

Why Pinnacle

Curb-mounted skylight work on a membrane roof is a specialty, and it rewards a certified installer who details it correctly. Pinnacle installs as a VELUX 5-Star Skylight Specialist, to the manufacturer’s specification. We’ve served Rhode Island since 2012, hold a 5.0-star Google rating across 100+ reviews and an A+ BBB rating — see our full credentials.

Barrington, Rhode Island

Barrington is a settled, tree-lined East Bay town of established neighborhoods and well-kept homes, where additions, sunrooms, and low-slope sections are common on houses that have grown over the decades. Those low-slope roofs are where Barrington homes most often develop leaks, and where a skylight can either brighten a dim interior room or become a recurring headache. Detailing the membrane and the skylight curb correctly is what decides which one you get — and it is the difference between a ceiling stain that keeps coming back and a bright, dry room for good. Explore our work across Barrington roofing services.