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How Wide Should Flashing Be?

Wondering why your roof is leaking and whether the leak is from where your flashing is located? Could it be the wrong size of flashing, which resulted in a water leak? Don't worry! We did thorough research to give you an idea of how wide a roof flashing should be.

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Roof flashing width depends on its type. The following are the types of flashing and their corresponding approximate widths depending on wind zone and roof pitches:

  • Apron flashing: 5 to 8 inches
  • Cap flashing: 2 to 4 inches
  • Barge flashing: 2 to 4 inches
  • Eaves flashing: 5 inches
  • Ridge/hip flashing: 5 to 8 inches

Flashing serves as protection from roof areas where roof itself can't cover. Proper installation is the key to preventing future water leaks. Continue reading as we delve into more detailed discussions about flashing width and its usage.

A lead flashing on slate style roof. How Wide Should Flashing Be?

Roof Flashing 101

Roof flashing is typically made of a flat, thin sheet of metal. It functions to divert water away from seams and joints and keep it from entering roof openings and cracks.

It is often necessary around chimneys and other penetrations, where brick walls meet your roof, and where flat roofs meet shingled areas. Flashing is typically installed on the top of the panels of a metal roof.

Types of Flashing

Custom metal flashing in metal made in roofing factory

How wide a flashing is will depend on numerous types of flashing that can be used for various purposes:

Apron Flashing

As the metal that connects a roof slope to a roof penetration such as a dormer or chimney, this flashing, when properly installed, will protect the most vulnerable areas of a roofing system.

The apron is the lower flashing piece that extends up the vertical surface of the roof penetration and covers the roofing material.

  • For low, medium, and high wind zones with a roof pitch of 10 degrees or above: Use 5 inches without measuring the soft edge.
  • For all roof pitches in extremely high and very high wind zones: You can use 8 inches without measuring the soft edge.

Cap Flashing

Concealing and protecting the upper edges of the membrane base flashing, cap flashing is typically made of metal and Ethylene Propylene Diene Monomer (EPDM) for the membrane underneath.

It is also used to conceal or protect the tops of various building components such as parapets or enclosed balustrades. The minimum cross-fall across a 5-degree slope is provided by this flashing.

Metal cap flashings should approximately be as follows:

  • 2 inches in wind zones of low, medium, and high.
  • 3 inches for very high wind areas.
  • 4 inches in extremely high wind areas.
  • When used as a balustrade, this measurement excludes the bird's beak and the drip edge.

Barge Flashing

Typically folded over profiled metal roofing and down the face of the bargeboard, ending with a drip edge, barge flashing simply stops, leaving the exposed end grain of the timber bargeboard.

The barge flashings must have the following minimum overlap over the bargeboard:

  • For low, medium, and high wind zones with a roof pitch of 10 degrees or above: Use 2 inches.
  • For roof pitches of 10 degrees or less for low, medium, and high wind zones, and all roof pitches for extremely high wind zones: You'll need 3 inches.
  • For increased wind zones, all roof pitches: Go for 4 inches.

Eaves Flashing

This flashing protects the facade from a variety of weather conditions on the overhang, at the side or ends, and at the edge of the roof. 

It supports the shingles and creates a drip edge on the roof, which helps direct water into a gutter or away from the facade.

  • In extremely high or very high wind zones with a roof slope of 10 degrees or less and a soffit width of 4 inches or less from the cladding—eaves flashing must be installed with long-run profiled metal roofing.
  • The flashing necessitates a 1.4-inch overlap with the backup gutter stand and a 5-inch backward extension beneath the roofing.

Ridge/Hip Flashing

At the peak of a roof, ridge flashing closes the space between the two slopes. For profiled metal roofing, the ridge and hip flashings must offer the same level of protection as the apron flashings.

The edges need to be correctly notched to meet a trapezoidal form and softly treated to a corrugated appearance. The edges have been turned down leaving a 0.20-inch space between the cladding and the flashing.

Here's the ideal flashing for the ridge:

  • Use 5 inches for low, medium, and high wind zones when the roof pitch is 10 degrees or more.
  • Approximately 8 inches for all roof pitches in extremely high and extra high wind zones, as well as low, medium, and high wind zones if the roof pitch is less than 10 degrees.

What Are Common Materials Used For Roof Flashing?

Stepped lead flashing roof gulley creating a water tight seal between roof tiles and brick wall

The following materials are typically used for roof flashing by most modern home builders, but the decision to use a particular material should depend on its durability, cost, and visibility to observers.

  • Aluminum: It is a durable, easy-to-form, and relatively inexpensive material. Aluminum is the best material for a chimney, valley, or base flashing. Still, it must have finishing to prevent corrosion, particularly when in direct contact with treated wood, concrete, or cement. Aluminum flashing requires a skilled installer because it must overlap to ensure a watertight seal.
  • Galvanized steel: It is inexpensive but not long-lasting. Chimneys and valleys are where mostly galvanized steel is utilized. You can paint your galvanized steel to match your home's other structures and roofing. However, we suggest not using it in harsh weather zones or on homes with long-lasting roof materials such as tiles because the flashing will require you to replace it long before the roof.
  • Lead: This is one of the oldest and most flexible flashing materials, but it poses a potential number of health risks and should only be used in locations that require long-lasting water protection. Lead is a durable material that you can find in chimney flashing.
  • Copper: This material is the most expensive and also the most durable. Additionally, it works well with most wood preservatives. The lead coating on copper accelerates the loss of quality. Copper is the material of choice for the majority of flashing applications because it doesn't need to be painted or given other treatments.

How To Maintain A Roof-Flashing

Roofer construction worker repairing chimney on grey slate shingles roof of domestic house

Always keep an eye on your roof, particularly the flashing. Investigate any potential leak locations. Prevention is usually better than repair. If you want to maintain the condition of your roof flashing, you can carry out these quick maintenance routines.

  • Fill the Holes: Even though flashing can withstand the weather, occasionally small holes will develop due to corrosion or wear. If this occurs, you only need to patch up the hole rather than replace the entire flashing. Remove any corrosion and sharp edges using a stiff-bristled brush. Next, use roof cement to secure a piece of flashing that is inches larger than the hole. To create a water-tight barrier, generously apply roof cement around the patch's exterior edges.
  • Fasten: Over time, the flashing on your home may be loosened or eventually removed. Either the metal wears away from the edge of the hole where the flashing was initially lockdown, or the screws holding it in place loosened. In either case, you'll have to buy screws made of the same metal as your flashing to fix this issue and screw them into the framing below to secure the flashing in place. To prevent water from entering your home, cover each screw head with roofing cement.

Should I Replace Flashing When Replacing New Roof?

Roofer applying caulk to house chimney flashing

It depends on how your flashing is currently functioning. Flashing needs to be replaced if it is rusted, has holes, or has been detached from the roof. Have a roofing contractor check its integrity.

To prevent leaks and costly repairs, the flashing must be replaced if it is in poor condition.

No matter how good your flashing is, we advise replacing it along with your roof at the same time. Traditionally, the flashing only lasts as long as the roof with proper installation. Even if it is currently in good condition, it might only have a few years left.

In Closing

Using the right width and type of roof flashing is important to perfectly fit your roof in a way that will maximize its usability. We hope this post will serve as your guide on how wide should a flashing be for designated types.

If you're planning on a roof replacement project, check out these other posts:

10 Best Colors For Metal Roofing

11 Roof Shingles Color Ideas And Options