When re-roofing your home, the proper installation of flashings and edge flashing details is one of the most important steps to a successful roof system. Wall cladding, such as metal siding, cedar shakes, stucco or EIFS wall systems cannot be removed easily and then reinstalled. This is one reason we suggest professional roofing contractors perform the work.

When discussing the curb of your flashings you have to consider the curb height. One of the biggest concerns is with skylight or roof penetration installation is the lack of curb height. If a skylight or roof penetration does not allow for adequate flashing height, extending the height of the curb is recommended.

On a steep-slope roof system, where a roof system is terminated at a wall, the use of appropriate base flashing and counterflashings, such as metal, cladding or siding, is necessary. If the height of the wall does not allow for proper installation of termination details, alternate flashing details will be required. For example, installation of a coping cap that acts as counterflashing may be an appropriate alternative detail. The most common flashings are:


Valley flashings
Valleys need sturdy flashings because they receive more water then other parts of the roof system. One of the most common valley flashing is a W-shaped aluminum or galvanized metal which comes in 10-foot lengths and in 16 to 24 - inch widths (as the pitch of the roof gets lower, the wider the flashing it will require).

On the majority of steep-slope roof systems, metal flashings are installed after the felt liner is in place and before the primary underlayment and finished roof system is installed.


Flashings for drip edges and eaves
A drip edge flashing keeps water from entering back under the roofing material along the eaves and rakes. Installing flashing on the drip edges and eaves is important factor to reduce damage from ice dams and snow build-ups.

Chimney Flashings:
Usually, chimney flashing have several parts: solid base flashing along the bottom of low side, overlapping step along ascending sides and continuous saddle at the base on upper side of chimney. If the roof system is particularly steep, a cricket should be used on the backside of the chimney. Failure to provide for adequate flashing height at the design stage may result in serious problems that cannot be subsequently corrected.
Many things affect the performance of the flashing system. They include the following:

• Compatibility between the base flashing and the membrane if they are of different materials.
• Difference in coefficient of thermal expansion between counterflashing and the wall or parapet to which it is secured, causing movement at the joints between one length of the flashing and the next. (This movement may be accommodated if only one end of the flashing is nailed. The remaining length is held with clips and the free end is secured with an S-lock joint. Failure to allow for free movement may result in failure of the fasteners or buckling of the flashing.).
• Failure of the reglet seals if caulking is not maintained or the counterflashing moves.
• Independent movement between the adjacent wall and the roof deck (some slack must be left in the base flashing to accommodate such movement and allowance must be made for the counterflashing to follow these movements independently of the base flashing).
• Movement of the membrane; the base flashing will either be drawn with it, in which case its upper edge will be pulled downward and no longer protect as the designer intended, or it will tear.