How to Install Flat Roof Flashing

Lead Image
  • 4-12 hours
  • Intermediate
  • 50-300
What You'll Need
Metal flashing
Roofing nails
Clear roofing epoxy
Tin snips

Flat roof flashing is a very important component of a roof and should never be ignored. Essentially, flat roof flashing is strips of metal that are bent at a 90-degree angle. Their main purpose is to act as a defense against rain, snow, ice, moisture and even some debris. A roofer would install flat roof flashing wherever a potential risk of either of these things exists. Follow the simple steps below to install flashing to your own flat roof.

Step 1 – When to Install

The purpose of flat roof flashing, as mentioned above, is as a defense against water from entering the building. It does this by covering potential access points like a chimney or vent. The metal flashing is bent and rests against the outside of the potential trouble area and fastened in place. In order to make the flashing effective, it has to be placed at the right time. After the plywood is placed and covered with felt is when the flashing is installed. In other words, it is placed so that it rests directly under the shingles.

Step 2 – Where to Install

Locate all of the areas around the flat roof where water can potentially enter. Look for the chimney or any type of pipe coming out of the building. This can be a source for anything from smoke to steam. Look for any type of vents as well. Flat roof flashing is also installed around the perimeter of the roof to protect the underside of shingles.

Step 3 – Trimming and Sizing Flashing

Once you have located the sites to protect, you will need to size the flashing which is done by cutting it. Get a piece of the flashing to cover, and line the edge up with the area and bend it around until it meets and overlaps the starting edge. Draw a line with a marker, and trim the excess with the tin snips. Flashing is aluminum, so it is very easy to bend in this fashion. The edge of the flat roof needs no modification, but each section you place should overlap slightly. For around pipe, use the tin snips to cut slits every 2 inches through one of the bent sides. You can then wrap it around the area and trim the excess.

Step 4 – Install the Flat Roof Flashing

Once you know where the flat roof flashing goes and you have trimmed it, the easy part is installing it. Place the flashing where you determined, and hammer it in place using roofing nails until the head of the nail is flush with the roof. The only real change is with the edge of the roof where the crease of the flashing is positioned to hang over the edge. Once the flashing is nailed in place, you will use clear roofing epoxy to essentially paint over the flashing. This will seal the edges of the flashing to prevent leaking.