 Water intrusion in building walls is the primary cause of premature building failure and the root cause of costly and time consuming litigation nationwide. Continual wetting and drying of wall cavities not only destroys wood fibers, but can provide a breeding ground for mold and mildew which foul the appearance and air quality surrounding the moist area. Intrusion can occur in all types of buildings and in most climates, typically at planar and material junctions in buildings, such as roof/wall junctions, door and window openings, and where architectural features meet cladding/veneer.
Flashing, a redundant barrier at the locations most likely to admit moisture, has long been the traditional approach to sealing architectural feature or material junctions. Today, there are numerous new flashing products available to assist building designers marry the increasing complexity of designs and products with off-the-shelf convenience for the tradesperson.
Roof Flashing
Many roofs have multiple intersections, such as valleys, crickets and abutment to adjacent walls, which are prone to water leakage. Pre-formed components such as drip edge, step flashing, kick-out diverters, and specialty pipe/chimney caps provide solutions that eliminate the guess work for specialty trades (e.g., roofers and siding installers) and streamline construction.
Pan Flashing
Window and door sills present another opportunity for water leakage from wind-driven precipitation. Industry experts have long recommended that these areas be flashed with water dams at the back and up the sides of the sills with a forward slope for positive drainage. There are many manufactured sill pan systems available on the market today. Often made of molded (and sometimes recycled) plastics, products include drainage channels to direct water away from the window frame that are available in standard opening widths and can be cut and customized on site. Some systems include trim strips so that any part of the system visible after installation can be covered for aesthetics.
Head Flashing
Window and door heads and transitions in cladding and architectural finishes present additional areas for water leakage. Head flashings can be field fashioned from rigid metals, like aluminum and copper, purchased pre-formed, or formed with cladding, dependent on window frame configuration and trim details.
There is a U-shaped brick veneer wall head flashing called Brick Pocket that has an integral 5-½ inch frieze board, J-channel, and a siding interlock strip. The flashing product eliminates the framing that is required for cornice nailing block build-outs with brick veneers, providing a maintenance-free finish and watertight barrier where the veneer meets the soffit transition. The flashing comes in the color white in 12-foot lengths and can be installed by the siding subcontractor before the masonry contractor installs the veneer. This flashing can also be used at window sills and gable walls with the J-channel removed.
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Pre-manufactured products can speed installation, saving labor time.
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Water-tight structures eliminate an opportunity for mold growth that could affect indoor air quality.
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Flashing prevents water intrusion, thereby reducing the likelihood of premature degradation and structural damage to underlying components.
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Builders need to do some relatively simple up-front planning to integrate pre-manufactured flashings and other redundant barriers into their home building process. Architectural plans should show clearly the location and type of flashing that has been designed at assembly junctions and openings. Trade contractor specifications should state explicitly who is responsible for providing and installing the flashings.
The price will vary depending on the specified product complexity and what the previous building practice/specification involved. Pan flashing prices range from $5 to $60 for each piece, though prices on the lower end are usually for individual components that are assembled in place, while prices on the higher end are for more complete, to-size systems. Kick-out diverters range from $7 - $12. Pipe and roof flashings range from $4 - $12 per piece for plastic components. Prices for metals like aluminum, lead, and copper can go much higher.
Not Applicable
Building codes have long required approved corrosion-resistive flashing in the exterior wall envelope of homes to prevent entry of water into the wall cavity at window tops; chimney/masonry intersection with walls; under sills; above wood trim; where porches, decks and stairs attach to a wall; at wall and roof intersections; and at built-in gutters.
None
Since fewer flashing components need to be manufactured on site, installation should take less time than traditional systems. Specific parts may require trimming to fit desired application, but overall are installed in the same manner as an on-site built flashing system.
Manufacturers warranties vary. Check individual products and install per manufacturer’s instructions.
Where pre-manufactured flashing components replace an approach that was customized in the field, there should be a labor savings that may offset the initial cost differential. If pre-manufactured flashings are not replacing another redundant barrier, there will be added first cost in the time and material to install flashings. However, eliminating water intrusion will enhance the building’s durability.
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