Copper

Residential roofing is typically made up of a multitude of materials and surfaces whose primary task is to maintain a barrier between the interior and the weather. The most pervasive and difficult weather element to control is water. Roof flashing is usually the last line of defense in the battle against water penetration.

Flashing forms the intersections and terminations of roofing systems and surfaces, to thwart water penetration. The most common locations for roof flashing are at valleys, chimneys, roof penetrations, eaves, rakes, skylights, ridges, and at roof-to-wall intersections.

Flashing must be configured to resist the three mechanisms of water penetration: gravity, surface tension, and wind pressure. To achieve this, flashing can be lapped shingle style, soldered or sealed to function as a continuous surface, or can be configured with a non-continuous profile to defeat water surface tension.

Flashing materials must be durable, low in maintenance requirements, weather resistant, able to accommodate movement and be compatible with adjacent materials. Common modes of failure include exposure to salt air, excessive heat, acid rain, heavy snows, and scouring winds.

Traditional materials and methods of installing flashing produce some of the longest lasting of building systems components. Those methods do, however, require experience and are time consuming.

Newer membrane materials and modern sealants are available that complement time-tested techniques, but, regardless of the methods and materials employed, the basic principles of roof flashing must still be adhered to, and the three water penetration mechanisms must be overcome.