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ROOF FLASHING AND LEAKS

What Is a Roof Flashing and Why Is It Important

While roofs are purposely constructed to allow rainwater run-off, they can often have several vertical features or protrusions, such as chimneys, parapet walls, half walls, dormers, skylights, vent pipes, and the like, where water can pool up and/or drip into the crevices between.  The areas can eventually become damaged and allow water seepage and leaks into the house.  To prevent this, professional roofers apply roof flashing to divert rainwater down the sides of the vertical surfaces, keeping the water from stagnating.

Roof flashing is typically a thin metal material fabricated from rust-resistant metal, such as G-90 galvanized steel, a frequently used flashing material, copper, or aluminum.  Depending on the company, flashing may even be available in lead or zinc alloy.

Steel, copper, and aluminum are particularly used because of how malleable these metals are, rendering them easier to shape. However, the homeowner should note the different characteristics of each metal:

• Galvanized steel is less costly than aluminum and copper, and is well resistant to corrosion. It is for these reasons that steel is most often chosen for flashing.

• Copper is quite durable, but it discolors into a patina over time. Some homeowners appreciate the classic appearance of copper with patina.

• Aluminum is easier for roofing professionals to shape and lighter in weight. Aluminum must be coated to be preserved. Bare aluminum breaks down when touching alkaline surfaces, such as mortar used to secure bricks. As long as the aluminum is coated, it can be used on concrete or stonework.

Flashing closes the joints between the roof and the roof features in order to protect the house from erosion and leaking.  A lack of flashing or poor flashing installation can also lead to wood rot, potential shingle damage, or deck collapse, among other issues.   The flashing will stay in place when nailed properly to only one of the surfaces, but nailing can create unnecessary holes in the roof structure.  An alternative that professionals use is roofing cement, which creates a waterproof seal between the roof and the flashing.

Flashing comes in various shapes and is used for different areas on the roof.  For this reason, different flashing types will be installed in dissimilar ways, and the cost of flashing will vary.  If the homeowner is uncertain about having flashing installed, it should be noted that alternative materials, such as sealant or tar, are ineffective long-term.  They break down, making the areas they are purposed to protect vulnerable to water. Flashing, on the other hand, is made for long-term use and, when installed properly, keeps the roof from blemishes and damage.

Types of Flashing

Flashing Materials Prevent Roof Penetration

Even small water leaks in key parts of the roof can generate much more damage to your home’s interior.  Painted walls and ceilings will first darken with moisture, and then the paint and plaster will start to bubble, flake, and even fall right off.  Those areas around which flashing details are placed will actively guide water away from those vulnerable areas and ensure leaks don’t happen.  Your quality asphalt shingles, well-constructed edges, and capable gutters should do the rest.  Whatever material your flashing is made from, it will need your care and attention.  If it does get damaged or too worn or is improperly maintained, it might work to channel water into your property and not towards the gutter where it’s supposed to go.

Flashing Works to Prevent Expensive Exterior Damage

Fixing a chimney isn’t a cheap job, and neither is having to replace dormer windows or skylights because of water damage.  Installation of a proper protective seal around the edge of these features will protect them just as well as your interior ceilings and walls.

Flashing Adds a Layer of Insulation to a House

One additional important factor is that by creating a seal around a skylight, pipes, vents, a chimney, and other exposed areas, homeowners get an insulating effect as those exposed cracks and gaps are covered up, and thermal movement stops.  That makes a building more comfortable and more livable.  Contractors understand that roofs can be the source of much difficulty for homeowners, but there’s a lot less to be worried about when proper flashing is installed.

Add Value to a Home

A home that has never had a roof leak likely owes that to the quality of the flashings that are installed upon it.  No past leaks means good news to potential buyers and will certainly increase the chances of buyers making offers.  Dealing with shingles, gutters, flashings, and related problems is something no buyer wants to think about.

What is the Purpose of Flashing on a House?

The purpose of flashing is to direct water from rain or snow away from vulnerable sections of the roof that are more susceptible to cracks and gaps.  Flashing most commonly comes in the form of metal flashing and can be made from various types of metal, such as lead, galvanized steel, or stainless steel.  Copper flashing and aluminum flashing are also available. There are several different types that aim to prevent a leaky roof by targeting different roof features.

Cap flashing

This flashing is used most commonly around a chimney.  Base flashing is first applied underneath to seal the gap, and the cap flashing then overlaps with that.  It’s also known as counter-flashing or cover flashing.

Step Flashing

This is flashing that is used for roof-to-wall connections.  It is installed in layers using rectangular pieces bent in the center to create a right angle to fit between the roof and a connecting vertical wall.  The purpose of this flashing is to direct water away from roof-wall connections.

Concealed Flashing

When you can’t see the flashing, it might be concealed within the structure for both aesthetic and practical reasons. One roof feature that typically uses this type is skylights.

Vent Pipe Flashing

Finally, we have the cone-shaped flashing installed right into your roof tiles to cover up pipes and shield them from rain and other precipitation.  These flashings and others are applied slightly differently and may be made from a different material, but they share the same protective function.  Besides rain, snow, and other water that might leak in, flashings also prevent debris from getting embedded in those same gaps. Such debris might be blown in by strong winds or even naturally fall off nearby trees, for example.

Can Roof Flashing Leak?

Yes, it can.  First of all, no matter if you have a flat or sloped roof, no matter the material your flashing is made from, no matter how professional the installation was, harsh weather like wind, rain, and snow take their toll on your roofing and gutters.  To prevent water leaks in the flashing, you’ll need to inspect the roof regularly, especially after periods of extreme weather.

Your home is like any other building, where every horizontal and vertical surface is exposed to the elements.  Base flashing can shift, shingles can shift, metal can rust, edges can become uneven, all of which can lead moisture to penetrate the roof and start affecting your attic or other interior spaces.  Inspect the roof at least once a year, plus an additional inspection whenever your area experiences unusual patterns of wet weather.

The most common cause of flashing leaks, however, is poor installation.  The elements will wear away at your roofing material over time, but mistakes made during installation remain the bigger problem.  For instance, a skylight that is measured wrong or sealed incorrectly will create problems sooner or later.  A single edge out of place, even by a fraction, can cause the entire roofing dynamic to be negatively impacted.

What is Chimney Flashing?

Flashings are the strips of metal that are placed along the front edge, corners and ridges of your roof and around your chimney and skylights. They are meant to create a watertight seal where your chimney and roof intersect. But, if the flashing was not installed properly, if it is subjected to a violent storm, or its sealant has deteriorated, it can start to pull away from your roofing material and lead to water leaks.

When to Replace Chimney Flashing

Ideally, you should have your chimney flashing inspected every 6 months.  This helps prevent leaks from wreaking too much havoc inside your home.  If your flashing is missing, rusted, visibly separated from the chimney, or completely covered with roofing tar (a quick stop-gap measure that may be covering up a larger problem), you should have it replaced.  Also, any time you replace your roof’s shingles, you should have new flashing installed, so that it lasts as long as the new roof.