Roof Maintenance, Roofing

How to Install Roof Flashing


Roof flashing is an important consideration when building your home. It helps to protect your roof against water leaks and seepage.

Installation of roof flashing is not peculiar to a new home. You can also install it when repairing an existing roof.

Most roof flashings are made of galvanized metals and aluminum. However, if you are installing it yourself, aluminum made roof flashings are recommended. This is due to the fact that it bends easily.

Since roof flashings serve as protectants, they are often placed on areas in your roof surface that require additional protection.

These areas are mostly intersections like; chimneys, vents, soil stacks, skylights, roof valleys etc…

So, whenever you are having leakage related challenges in your home, check out the aforementioned areas first.  

Sometimes, the existing flashing could be having issues like nail work lose, flashing pulled away from the roof or in bad shape. If the flashing is in bad shape, replacement should be considered.

Installing the Roof Flashing

Installing your roof flashing differs, depending on the type of flashing and where it is being installed.

Step Flashing For Chimneys

Step flashing helps to protect the intersections between the roof and the chimney. It also protects the skylights. Below are details on how to install step flashing for chimneys

You can only install step flashing on chimneys after you install the shingles. Once the shingles are installed, lay the flashing about 4 inches past each end of the chimney. After this, incise the first flashing to bend properly so that it can go round the front of the chimney, its side as well as the base.

Once you perform the step above, use plastic roof cement under the base part of the flashing. After which, you attach it to the roof with galvanized roofing nails.

At this point, the piece of flashing that bends around the chimney will not be attached to anything. And you have to do this process again and again around the length of the chimney. Don’t forget to always cut each flashing to bend properly.

The next step is wrapping a counter flashing around the entire chimney. Usually, you need to attach steel masonry fasteners to the counter flashing. Well, this depends on your chimney flashing kit directions.

As a rule, always leave about an inch gap between your shingles and the bottom of the side flashing. And use plastic roofing cement to seal the top of the counter flashing and any other gap you discover.

Valley Flashing

Valley flashing is used in the valley area of a roof. If you live in a snowy area, you have to consider laying a waterproof membrane before applying a valley flash to your roof.

When laying a waterproof membrane, arrange it on your roof according to manufacturing instruction. After you have done this, set your flashing on it.

Flush your flashing with the drip edges at the bottom of your roof’s valley once you lay it down. When you lay it down, use tin snips to trim it properly and nail it along the outside edges.

Note: Don’t nail the flashing in the middle.

Once you are done with this step, seal the seams and nail heads with roofing caulk for extra protection.

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