Flashing

From Roofing, Solar Power, and Spray Foam Insulation Wiki

Flashing

(1) Components used to weatherproof or seal the roof system edges at perimeters, penetrations, walls, expansion joints, valley, drains, and other places where the roof covering is interrupted or terminated. For example, membrane base flashing covers the edge of the field membrane, and cap flashings or counterflashings shield the upper edges of the base flashing.

(2) Pieces of metal or roll roofing used to prevent seepage of water into a building around any intersection or projection in a roof such as vent pipes, chimneys, adjoining walls, dormers and valleys. Galvanized metal flashing should be minimum 26-gauge. There are 4 main types of flashing used in residential roofing systems

(3) Weatherproof material installed between roof sheathing (or wall sheathing) and the finish materials to help keep moisture away from the sheathing.

Valley Flashing
This flashing is used in open valleys of the roof. Most often leaks are found in the valley flashings due to flashing that is nailed to tightly to the decking or shingles that are not trimmed far enough off the flashing.

Plumbing Vent Flashing
Plumbing vent flashing prevents rainwater from running into holes cut for pipes in the roof. This flashing is sold according to the size of the vent pipe and the roof angle. Roofing material is installed over the flashing.

Lead Flashing
When working with tile roofs, lead flashing is used. In the case of a plumbing vent flashing, the lead flashing is actually molded to the shape of the tile's surface. Then the top of the lead flashing is covered by the next tile to prevent water from seeping under the flashing.

Step Flashing
When a chimney or dormer wall intercepts the slope of the roof, step flashing is used. Step flashing is usually a metal piece that is bent in the middle, so that one end lays on the roof, and the other against the vertical wall of the dormer or chimney.

• Flashing Is One Of The Most Important Elements Of The Roof Because It Seals The Seams And Joints Of The Roof--The Locations Where Leaks Are Most Likely To Occur. Often, Flashing Is Not Maintained Well, Or Installed Correctly In The First Place. Check For The Following Signs That Your Flashing Needs Maintenance Or Repair

Flashing Cement

As used by the roofing industry, an ASTM D 2822 Type II roof cement that is a trowelable mixture of solvent-based bitumen and mineral stabilizers that may include asbestos or other inorganic or organic fibers. Generally, flashing cement is characterized as vertical-grade, which indicates it is intended for use on vertical surfaces. (See Asphalt Roof Cement and Plastic Cement.)