The major purpose of any roof is to keep out the rain. For many the only time they give their roof any thought is when it falls in this one duty. Many people see the roof as a single thing, a layer of shingles nailed to a wooden plane. But it’s a lot more complex than that, especially when you account for the fact that most roofs aren’t a simple uninterrupted plane. They have ridges and valleys where two planes meet, they have holes cut into them for chimneys, vents, and skylights, and the edges of the roof themselves. These areas are vulnerable not only due to the edge of the shingles, but also because these areas are under additional strain when it rains, as the water channels and pushes extra hard at many of these locations. This is where roof flashing becomes critical to the roof’s ability to protect your home.
What is Roof Flashing?
Roof flashing is a weatherproofing material designed to go over the joints in a roof. It is usually made of galvanized steel or aluminum, though copper and zinc are also sometimes used. Flexible synthetics such as rubberized asphalt, butyl rubber, and acrylic are also used, depending on the circumstance. This material is placed over the joint, and under the shingle, after being bent or cut to shape, then secured to the roof with roofing staples or nails. Some exact methods of installation change depending on the joint(s) the flashing is securing.
Typical Locations of Roof Flashing
Flashing occurs anytime there is a break in the roof into which water might seep. Few roofs can get away with only flashing where two roofing planes meet, but instead have multiple gaps due to the home’s chimney, kitchen vent, or the occasional skylight. Here are common locations for flashing, and how the flashing installation differs from location to location.
- Chimney: The chimney uses two types of flashing methods. On the front and back where it is level with the roof it uses continuous flashing, but on the sides it uses the step method. L-shaped sections of flashing as wide as the length of shingles are layered overlapping beneath the shingles with the angle of the flashing resting against the chimney, forming “steps” up the side.
- Valley or Ridge: Whenever two major planes meet, such as the ridgeline of the roof or a valley from a porch extension, form a long line joint that needs to be capped. These flashings are always underneath the shingle.
- Vents: The venting pipes tend to be circular in nature, which would defeat the traditional flashing. Most vents instead come with their own flashing cover that is installed over the vent, and then covered by shingles cut to fit.
- Skylights and Dormers: With these large box designs, the front is a continuous flashing. On dormers step flashing is known to be used on sides, but skylights usually have specially cut flashing for the corners to provide additional durability from leaks.
- Sheathing: Where the roof ends and paint begins is a last line of flashing, a cusp going around the perimeter of the roof and preventing water from seeping into the wood of the overhang.
Listen to Kelly Shepard, owner of All Weather Tite Roofing, Siding and Windows explain the right way to install roof flashing to prevent leaks and ice dams.
The proper way to install flashing
We hope this answered your questions about exactly what roof flashing is and what it does. If you have any additional questions about roofing – roof flashing or otherwise – or are in need of repair or replacement of your roof flashing, shingles, roof, or would like a free estimate on the state of your roof, please contact All Weather Tite and we’ll get someone out to help you, in a flash!