Roof Flashing Basics
Roof flashing provides extra protection against moisture penetration and is an important feature to utilize, monitor, and repair. Learn all about different types of flashing, the materials used, how to install it yourself, and more.
Main Types of Flashing
Flashing is applied around the chimney in a few key areas: continuous flashing along the bottom, step flashing up the sides, and saddle flashing along the top. Caulk or cap flashing laps over the edges to prevent water from running behind and causing leaks.
Continuous flashing is installed to protect the joint between a vertical wall and sloped roof.
Drip edge flashing is used to prevent water from seeping under the edges of roof rakes and eaves. This flashing is installed under the roofing felt along the eaves and over felt along the rakes.
Like chimneys, skylights have their own flashing system. Flashing is placed along the base, sides, and saddle across the top.
Step flashing is installed to protect the sidewalls of chimneys, skylights, and roof dormers. It consists of a series of right-angled metal pieces. Each section is composed of metal-like shingles that overlap the section beneath it. Step flashing’s vertical edge is placed under siding or capped along the second counter flashing mortared into the chimney or caulked along a skylight so water can’t penetrate behind it.
A critical point for flashing installation is a valley where two roof planes meet. Shaped like a “W,” this channel is placed over the top of the building felt before the roofing’s material is put down.
Pipe and Hood Vents
Vent flashing, whether piped or hooded, is installed by cutting a hole the roof. After placing the preferred venting option, flashing is installed under the shingles above the vent and the joints are sealed.
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Certain areas of the roof and roofing system are prone to water damage, leaks, and moisture penetration. Skylights, roof valleys, and chimneys are regular spots where water runoff is heavy and can benefit greatly from the extra protection of flashing.
Flashing is most commonly fabricated from rust-resistant metal, like aluminum, copper, or galvanized steel. On occasion, flashing may be made from plastic, rubber, or roofing felt. Flashing's composition can vary depending on its location on the roof.
Aluminum flashing is great for DIYers because it’s easily malleable. Galvanized steel is a favorite among contractors, and copper flashing is used to match copper roofs.
DIY Flashing Installations
Some homeowners decide to tackle flashing installations themselves. While capable DIYers can tackle flashing installations, flashing is more than just some scrap metal, roofing glue, and a handful of nails.
Do your homework and know what to look for if you plan on replacing flashing sections yourself. Be on the lookout for dry, crumbled shingle edges, cracked corners, and rotted wood.
Flashing needs to overlap from one piece to the next, allowing water to run off the roof rather than slip beneath roofing materials. New flashing can be installed with roofing cement, nails, or both. But, if it’s installed incorrectly, the cement can erode or the nails can cause holes in your roof rather than hold the flashing in place.
Like any aspect of your home, you should regularly inspect roof flashing. The next time you clean your gutters, take a few extra minutes to walk the roof and inspect flashing installations. Regular maintenance and early repair prevent leaks from occurring. Obvious problems can be spotted from the driveway, or show up as a leaking ceiling.
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Trust a Knowledgeable Professional
Cracks and holes along flashing need to be repaired as soon as possible. A small leak can quickly turn into serious moisture problems damaging the attic, ceiling, and interior walls. It's never a bad idea to hire an accomplished professional to handle flashing installations and repairs.