Roof Flashings Done Right (2024)

Step flashing, chimney flashing, and pipe flashings keep water out of the roof, but only ifinstalled well

John DeRosa of IKO Roofing talks aboutthe right way to install flashings.Improper flashing techniques are susceptible to leaking. Andnobody wants to see that on a new roof. So, here's what you need to do to help ensure this doesn'thappen to you.

Step Flashings

Roof planes that butt against vertical walls at the end of the shingle course are protected by metalstep flashing at least 5” high and 5” wide. When applying the new shingles, each shingle course willbe covered by a step flashing.

There are two simple rules to follow:

1. Each flashing should overlap the one below by at least 3” but not be visible below the shingle toplap
2. Embed each piece of step flashing in a 3” wide application of asphaltic plastic cement and nail in place.

Then the end of each shingle overlapping a step flashing must also be well embedded in plasticcement.

The metal step flashing shingles are rectangular in shape and style, approximately 10” long, and atleast 2” wider than the face of the shingle being used. For instance, when using metal flashingshingles with a typical 5 - 5/8” exposure, the size of the flashing will be 10” x 8”.

The 10” length is bentin half so that 5” will reach up the wall surface and the other 5” will extend onto the roof deck.

Note:Other step flashing sizes are also acceptable.

To install the flashing shingle on the first course:

• Place it over the end of the starter strip.
• Place it so that the tab of the end shingle covers it completely.
• Secure the horizontal flange to the roof deck usingtwo nails. Do not fasten the flashing shingle to the vertical wall. This will allow the flashing shingle tomove with any expansion and contraction that may occur with the roof deck.
• Place the second stepflashing shingle over the end shingle in the first course by positioning it 5-5/8” above the bottom edgeof the exposed asphalt shingle. Make sure that the tab on the shingle in the second course will coverit completely.
• Secure the horizontal flange to the roof.
• The second and succeeding courses willfollow with the end shingles flashed as in preceding courses.

Other common roof flashings

Chimney flashingsare secured to the roof over the top of the shingles, and counter or cap flashings aresecured to the chimney, providing a waterproof seal.

Pipe flashings around soil stacks:

• Shingle up to the bottom of the stack.
• Apply plastic cementaround the edges, and then slide the new flashing over the soil pipe and into place.
• Nails used tosecure flashings to the roof should be used sparingly, not driven close to the pipe, and placed whererecommended by the manufacturer.
• Continue shingling and cutting to fit around the stack.
• Each cut shingle should be laid in a bead ofcement.
• A dab of plastic cement over the exposed nails is recommended to avoid leakage.

As we can see, the measurements and application of products used when installing roof flashing arecritical to creating the protection that is sturdy but also flexible enough to adapt to changing conditionsof the home or structure, right down to the shingles used for flashings.

Note: This video was filmed in an indoor studio on a prefabricated deck; all safety guidelines outlined by Government Safety and Fall Protectionstandards must be followed at all times.

—This video is provided byIKO Roofing, a worldwide leader in roofing and waterproofing.