Ultimate Guide To Roof Flashing

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Ultimate Guide To Roof Flashing

Ultimate Guide To Roof Flashing

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Although rain is harmless on its own, it can create severe damage to your roof.

Wind, rain, and sunlight exposure are elements your roof continually protects you from. And let’s not forget all the hail that drops a literal load just to say hello during winter.

With that in mind, you might be wondering…

How Does Roof Flashing Protect My Home?

Flashing keeps water away from seeping into your home, and it protects your roofing materials as well.

Without flashing, water could easily seep inside, and believe me, apart from the damaged aesthetics, your home interior and expenses will be a serious problem.

The culprit behind most roof leaks is improper flashing installation.

With improper flashing, water can easily seep underneath your shingles and cause water damage to your roof deck or any other materials used to construct your roof structure.

So what is flashing on a roof? And how does it look like?

The materials used for flashing are usually a thin metal sheet like galvanized steel surrounding critical areas of your roof. These critical areas are:

  1. Roof protrusions – This refers to your skylights and bathroom kitchen vents
  2. Sidewalls – A space in your roof where the roof surface meets the wall
  3. Valleys – Also known as the place where two roof slopes meet
  4. Roof Edges – This refers to the rakes and eaves in your roof

Of course, flashing isn’t a linear process or job. There are different types, techniques, and materials used to flash your roof.

In the next sections to follow, we’ll discuss how these apply to different areas on your roof and the best techniques in the installation process.

Types of Roof Flashing

The two main types of flashing on roofs are base and step flashing. Drip edge flashing and valley flashing are also standard options.

Just so you know, there are 8 flashing types! Sounds like a lot, doesn’t it?

To protect your roof and home, you’ll need all the knowledge you can possibly consume to stop those replacement & maintenance costs from piling up.

Base Flashing

Base flashing is useful for areas in your roof where the roof surface meets a vertical surface such as a wall or parapet. Installing base flashing is usually found at the joint between the roof surface and wall or parapet.

This is a common type of flashing on roof chimneys. Chimney flashing is quite hard to work with, and it also needs two pieces of flashing.

Why two pieces? Because when the rain starts to fall on your chimney, the flashing surface directs the water downwards to protect any seeping.

Most professionals will use base flashing for front walls wherein the flashing matches your roof’s pitch.

Step Flashing

Step flashing is essential and useful for areas where your roof deck meets a sidewall. In fact, step flashing should always be used in these areas.

The piece of flashing used like copper, for example, is bent 90 degrees at the center, and are installed in layers along with the shingles to ensure protection.

Valley Flashing

It’s easy to spot a valley on your roof. When two roof decks meet, it creates a low line. This low line looks like a valley caught between two mountains.

Valleys are among the most common areas prone to water damage, making proper valley flashing installation a must. Valley flashing is mostly being replaced by ice & water shield.

valley flashing example

Drip Edge Flashing

Another essential type of flashing for your home is a drip edge. Having a drip edge protects your drywall and fascia board. It’s also just as crucial if you want to keep water away from overfilling your gutter.

You’ll find a drip edge installed on the eaves or edges of your roof and will also help water drip off the edges without causing damage to your home.

drip edge flashing

Continuous Flashing

Continuous flashing is a type of flashing that works like an apron. The piece of flashing used are long pieces of metal that keep water from damaging your home by directing it down to the shingles below.

The drawback of continuous flashing is that temperature fluctuations can cause the pieces of metal to expand and contract. As a result, this affects its performance in preventing any water leaks and seeping from happening.

Fortunately, most materials used for continuous flashing have built-in expansion joints to counter the expansion effect.

Counter Flashing

In roof chimneys, counter flashing is the commonly preferred method. Counter flashing is also the second piece and completes the two-piece system. It’s installed above the base flashing.

Skylight Flashing

Skylight flashing is a custom-made flashing by roofing manufacturers, or in some cases, they’re part of a package deal when you install flashing in your home.

Transition Flashing

Transition Flashing is needed when you have two different roof pitches that meet. It will direct the water over the flashing and on the new pitched roof surface.

transition flashing

Kickout Flashing

Kickout flashing is the bridge that connects the gap between where step flashing ends and your gutter begins. How it works is by directing water from the wall and into the gutter.

Vent-Pipe Flashing

Pipe flashing is specially made to tackle water leaks that occur in vent pipes, hence the name. Vent pipes are common areas for roof leaks, and what pipe flashing does is use flashing boots to seal around the pipes.

For a better installation and improved sealing, use flashing tape and any additional underlayment with the flashing boots.

Materials Used

Lead-coated materials were all the rage back in the old days; however, evolution is always moving forward. The following materials are the main types used when flashing a roof.


Aluminum is a flashing material that’s both easy to use and lightweight. Although aluminum is easy to install, using aluminum in coastal areas or places that come in contact with alkaline surfaces will cause it to degrade and corrode quickly.

If used with masonry and concrete, make sure to coat the aluminum material to prevent corrosion.


Steel is a popular choice for metal flashing. It provides excellent aesthetic value and malleability. When galvanized, it becomes corrosion-resistant.


Last but not least, copper is a solid material to use for metal flashing. It has high durability, malleability, and can handle soldering well. In addition, it has a long life span.

The only drawback to using copper is its discoloration. This is mostly preferential, though. Finally, you’ll find copper as the primary material used for chimney flashing.

Roof Flashing Techniques

Now that you’re familiar with the different types of flashing and the materials used to prevent water leaks & damage let’s proceed to the primary techniques you should take note of.

For the best home improvement results, refer to these techniques.

Counter Flashing

Counter flashing goes hand-in-hand with base flashing, and as mentioned earlier, it’s a two-piece flashing system. It’s a primary technique used to flash a roof’s chimney.

To explain further, the bottom flashing piece sits at the bottom of the chimney while the counter flashing piece is attached to the masonry of the chimney.

The reason behind why counter flashing should sit above the base flashing is to make sure water doesn’t seep behind the base flashing.

For any chimney flashing installation, professionals recommend this two-piece system to effectively protect your roof deck and minimize replacement costs.

Step Flashing

Step flashing is, without a doubt, an essential roofing technique to always use. The best use of step flashing is when your roof surface meets a wall, which should always be present in any home.

Without it, water could easily seep in from the wall and underneath the layer of roofing shingles. Step flashing ensures that water is directed into the gutter rather than your roofing shingles.

Vent Flashing

Vent flashing is used for a specific and critical area of your roof. Vents require a particular technique of roofing to adequately address any potential water leaks and seeping.

With vent flashing, the shingles are installed over the flashing boot. This usually follows a cylindrical design that surrounds and is embedded around the vent.

The boot’s height also matters since its primary purpose is to force water around the vent rather than in it.


When Should I Repair a Roof Flashing Leak?

Here’s what you need to look out for:

  • Corrosion and rust
  • Damaged or small holes
  • Any noticeable cracks and dents
  • Mold or Mildew growth
  • Damaged or cracked shingles
  • Damaged Fascia board
  • Water damage
  • Missing nails or pieces

You’ll notice most of these signs in your exterior walls or siding. Check to see if you see any paint bubbles, mold growth, or water stains.

Rust and corrosion are clear indicators that roof flashing replacement or repair is needed. Rust causes materials to break down and bend easily. Prolonging this will lead to even higher roof flashing replacement and repair costs.

Finally, don’t perform the roofing inspection on your own. Call a professional to assess your roofing and roof flashing as soon as you notice minor signs.

A roofing professional will be able to discover potential flashing issues that may be unnoticeable to the untrained eye.

How Much Does Roof Flashing Cost?

Home improvement doesn’t come cheap. Still, roof flashing is an important step you can’t neglect simply because it’s expensive.

If it’s expensive now, your home improvement and roofing costs will only become more expensive the longer you wait.

Roof Flashing costs depend on many factors, such as:

  • Materials and type of flashing used
  • Ease of installation
  • Scope of labor and damage
  • Location of flashing damage

For example, steel sheet metal is more expensive than using aluminum. Specific areas that need repair or replacement, such as vent or valley flashing, will cost less than step flashing the entire roof.

Expect to pay $200 to $500 for chimney and skylight flashing. Step flashing, on the other hand, depends on the scope of the project and how much step flashing you would need.

Other roofing materials used along with labor, tools, and miscellaneous fees of the home improvement process such as transport and accessibility of materials all matter.

Overall, costs can range as low as $50 to $500. Then again, this will mostly depend on the assessment of your roofing professional.

Moving Forward…

Roof flashing is as vital as installing or replacing a new roof.

It is essential to the home improvement process, but it’s also a key element in providing proper roof maintenance, mainly by protecting your roof deck and structure.

Be sure to consult a professional in your area and what steps need to be taken based on the inspection.

Flashing repairs are not to be taken lightly, and if acted on right away, this will save you a lot of hassle and long-term costs in the long run.

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