What Is Flashing On A Roof?


Are you aware of how crucial flashing is to the integrity of your roof? Maintaining your roof includes inspecting it regularly, as it is very important. But what is it?

It is best described as a thin metal layer used to divert water away from certain parts of a roof, such as chimneys.

Generally, they make flashing from non-corrosive metals, such as aluminum, lead, or steel. Copper is sometimes used for custom roofs. Other materials include rubber, plastic, and roofing felt.

Flashing is sealed to prevent water from seeping under it and damaging the roof. Call someone like us if you are in need of new residential flashing. We will make sure the flashing is installed correctly. 

What Is The Purpose Of Roof Flashing?

The flashing around skylights, chimneys, and vents is installed by roofers to prevent water damage. This prevents water from escaping from the seams or areas around these features, causing major damage. A roof’s flashing carries water back onto the shingles and eventually into the gutters or off the sides. 

Flashing can be crucial to the long-term stability of your roof. A single point where water constantly enters could eventually lead to rotten roof boards, along with water damage in the home itself. It may be necessary to tear off the shingles and replace many of the materials beneath, which can be costly. 

When a roof leaks, poorly installed flashing is often the culprit. It can even lead to the collapse of decking materials, which is why local building codes cover flashings.

Do you Need New Roof Flashings? 

The amount of flashing your roof needs can be determined by a professional roofer. Certain aspects of roofs are more prone to leaking than others. A roof valley, where the wall of a dormer meets the roof, and skylights are among these. Vulnerable areas like those chimneys and any other features that lead to high amounts of rain runoff need to be sealed with flashing.

Over or Under Shingles: Where Does The Flashing Go?

Typically, they install flashing under roofing materials such as shingles. To carry water down a roof valley, the flashings are placed between intersecting roof edges. Multiple metal flashings are placed around a chimney. Mortar is used to attach them to the chimney. Usually, they are shaped like an L. Shingles are then laid over the horizontal part of the flashing. Together, they should direct water away from the roof. Flashing can, however, sit on top of the shingles on the front of a chimney and cause damage.

Flashing is also installed around vents and pipes. After that, they apply a watertight seal to the pipe itself. 

Roof Flashings: What Types Are There?

Various types of flashing are available for different types of roofs. Some examples are: 

  • Apron or Continuous: A long metal section often containing expansion joints.
  • Valley: Located where two roof sections meet in a valley.
  • Base: Installed at the bottom of a chimney or similar feature requiring several pieces of flashing.
  • Counter: Used on the slope and sides of features like chimneys in combination with the flashing.
  • Skylight: Flashing made to protect skylight seams.
  • Step: Often used in conjunction with “kick-out” flashing, which channels water from a wall into a gutter.

What Types Of Materials Are Used For Flashing?

Flashing can be made from many different materials. As long as it is resistant to degradation by incompatible materials and impervious to water, any material should work.

The following types of materials are commonly used by builders:

  • Aluminum is lightweight, durable, and relatively inexpensive. However, corrosion occurs if aluminum is in contact with alkaline materials such as concrete or fiber-cement siding. 
  • Compared to aluminum, copper is more expensive and more difficult to form; however, it is extremely durable. 
  • Lead is soft, therefore it is easy to bend. It is durable and is a favorite of masons for chimney flashings. However, it poses some health risks.
  • Although galvanized steel is inexpensive, it isn’t as durable as other options.
  • Polyvinyl chloride is easy to work with and non-toxic. The polyvinyl chloride does not react with treated wood, which is a great advantage when building decks.

How Can I Fix a Leaking Chimney?

There are several causes of chimney leaks, including roof and masonry damage. A good way to detect a broken chimney flashing is to check the metal or seal of the masonry around the flashing. Water can be absorbed by masonry, especially if your chimney is made of stone. A soaked masonry will leak water if it becomes saturated. A leaking chimney may also be caused by imperfect mortar joints. Lastly, the chimney crown can crack and need to be repaired.

Final Thoughts

Are you worried about a problem with your roof flashing? Just request a free estimate by calling us at (636) 699-0449.