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What is skylight flashing?

It's the first layer of defense against rain and wind.

Cutaway showing three layers of protection on a VELUX No Leak skylight

What do we mean by No Leak skylights? Three reasons to feel confident about adding VELUX skylights to your home. As the first layer of protection in the VELUX No Leak system, the purpose of skylight flashing is to keep as much moisture on the surface of the roofing material as possible. VELUX skylight flashing kits are designed to shed water without relying on sealants that can break down over time and cause damage to your roof.

How is flashing installed?

Flashing is a vital component in any proper skylight installation. It’s so important that we require that our skylight flashing kits be purchased along with your skylights and installed properly to benefit from the 10-year “No Leak” installation limited warranty. Luckily, no matter the roofing materials you use or the type of skylight you select, we’ve got you covered with both deck mounted and curb mounted skylight flashing kits.

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This is an example of a flashing kit for use on an asphalt shingle roof.

Before the flashing is installed, VELUX skylights have two additional layers of protection that must be installed to qualify for the No Leak warranty. For deck mounted skylights, the deck seal is nailed directly to the surface of the roof and all-weather underlayment (think massive strips of very durable tape) are adhered over the deck seal, up the sides of the skylight and over the surface of the roof around the skylight.

Curb mounted skylights include a gasket that forms a tight seal between the curb and the skylight, and the curb onto which the skylight is mounted is wrapped in all-weather underlayment before it’s flashed.

Since most people hire a skylight installer, they can’t see firsthand how the flashing is installed. We’re happy to nerd-out with you on the details of this important skylight installation technique. In the end your skylight will be weather tight and worry free.

The flashing kit has three components: sill flashing, step flashing and saddle flashing. The installer starts at the bottom of the skylight with the sill flashing.

After a row of roofing material is installed over the bottom edge of the underlayment, the sill flashing is placed at the bottom of the skylight. The shingles must be installed close enough to the skylight so that the bottom flashing has proper coverage. Then it can be secured with roofing nails.

If you have a fixed skylight, the rubber gasket located at the bottom of the skylight should be pulled over the sill flashing to allow for proper water drainage. Once the sill flashing has been secured, shingles and step pieces are interweaved up the side of the skylight and each nailed to the roof surface with two nails. The first nail should be near the edge farthest away from the skylight frame, at least half way up. The second nail should be near the top edge of the skylight, but not too close to the skylight frame.

Occasionally, the top step piece will extend past the top of the skylight, but don’t skip this step piece. It should be cut to the appropriate length, so that it fits below the top edge of the skylight.

After the shingles and step pieces have been installed to the top of the skylight on both sides, the claddings that were removed at the beginning can be replaced around the skylight.

Once the cladding is in place, the saddle flashing is installed and should fit over the claddings. The claddings are then secured to the saddle flashing by bending the tabs and folding them over so that they fit into the slot on the saddle flashing.

Finally, the top flashing gets interwoven with the underlayment that covers the roof surface and the roofing material is added back around the skylight with a 2 ⅜ - 4 inch gap between the top of the flashing and the bottom of the shingles. Watch the entire process in this video showing the installation of a deck-mounted VELUX No Leak Solar Powered "Fresh Air" skylight.

Why is flashing essential to a watertight skylight installation?

Flashing is ultimately what gives VELUX customers the confidence that our skylights will not leak. Without properly installed flashing, you risk water seepage that can cause significant damage which may or may not be apparent immediately. Flashing protects your roof and home beneath from structural issues that no homeowner wants to deal with, like rust, corrosion and mold growth. Ensuring proper flashing installation is not just a good idea, it’s absolute best practice.

Learn more about the three layers of protection essential to VELUX No Leak skylights.

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