What is Roof Flashing?

Parts of a Roof | July 30, 2021  | By: John Esh

Roof Flashing Explained

Roof flashing is the material that seals the joints between your roofing materials (shingles, slate, cedar shakes, etc.) and any walls, penetrations, and edges.

Roof flashing is a part of every roof system that protects the home from water penetration. On all sloped roofs, flashing is most commonly made of metal, specifically aluminum, steel, and copper. On flat roofs with a membrane system such as rubber (EPDM), the flashing is made of pliable EPDM flashing, known as flashing tape.

While it’s best practice to install flashing with every roof system, this wasn’t always the case. Some homes with older roofs may have incorrectly installed flashing or may not have any flashing at all.

flashing, where roof meetings siding, replaced by joyland roofing on an asphalt shingle roof

Where is flashing on a roof?

Flashing is placed on the most vulnerable areas of your roof that are subject to leaking. These areas include shingles going up against a:

  • Wall
  • Chimney
  • Open valley
  • Pipe boots
  • Other objects or penetrations

When do I need to replace my flashing?

It’s too common for many roofing companies to not replace the flashing when they replace the shingles on your home. This can be fine! What is most important is that during the roof inspection, they determine the remaining life span of the flashing and replace as needed, like Joyland Roofing does.

Replacing your roof does not necessarily mean that the flashing will also be replaced. The most common flashing material on a steep roof is aluminum. Since aluminum does not rust/corrode, the wall flashing can usually be reused. 

Because of how wall flashing is often installed behind siding, it’s not always possible to replace it without  also replacing the siding.

Regardless of the difficulty, we always inspect the flashing carefully, looking for torn and damaged pieces. These pieces get replaced so we’re sure the roof system is 100% watertight. If the flashing is rusted (steel), it should be replaced. 

The types of flashing that should ALWAYS get replaced with the roof are at areas like:

newly installed pipe boot with flashing

– Skylights – we recommend replacing the entire skylight with the roof (see skylight post?), but at a minimum, the flashing around the skylight must be replaced.

– Pipes – Standard pipe flashing, or pipe boots, usually don’t last much beyond 20 years and so must be replaced with the roof. At Joyland we offer the Ultimate Pipe Boot which is a lifetime product which doesn’t deteriorate like other pipe boots.

– Chimneys – Chimney flashing is critical and should be replaced.

– Valleys – Valley flashing will be damaged while the old roof is being removed, so this should always be replaced.


How do I know if my flashing needs replaced?

You’ll want to identify any signs of aging. These vulnerabilities can lead to larger and more complicated problems in the future. Some clear indicators that you’ll need to install new flashing with your roof replacement:

  • Rust 
  • Holes or indentions
  • Surrounding shingles are lifted

Talk to Joyland Roofing

Flashing installation is included in our roof replacement quotes! Our expert inspectors confirm the best roofing solution for your home or business. Ready to talk to a sales consultant?

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    Pennsylvania Home Improvement Contractor License (HIC) # PA124258