Guide To Types Of Roof Flashing And When To Use Them

The primary purpose of roof flashings is to keep water out of the places which they have no business being in.

Otherwise water would be like a cancer slowing devouring the house from the inside out.

This is why flashing is essential to the keeping of a house in good condition.

They are generally installed when:

  • Roof material changes direction
  • Different materials meet
  • At joints and penetration points

While installing flashing is not the most exciting part of roofing, it is one of the critical components that a roof cannot do without.

Materials for roof flashing

Different types of materials cater to the different needs of homeowners.

This can depend on the type of roof, climate, household budget, etc.


The biggest advantage of aluminum is it’s malleability.

The ease of which to shape it makes it a suitable material unconventional roof shapes and overly creative designs.


While copper is not exactly expensive, there are cheaper alternatives that perform better.

Homeowners who choose cooper flashing usually do so for aesthetic purposes.

Maybe it just looks better with the roof material. Or that the roof is made of copper too.

Galvanized steel

This is a very popular choice as it is affordable, performs really well in durability tests, and highly resistant to rust.


PVC and plastic is also a common option considered by home owners due to it’s ease of customization and economic pricing.

However, they don’t work well with asphalt which is a popular material choice for shingles.


The biggest drawback with rubber is that it’s flammable.

Not that the roof would be exposed to an open stove every day. But when accidents happen, rubber on the roof can really make a bad situation worse.

Where flashing is used

Common sense would enable most people to identify where roof flashing needs to be used.

But for more clarity, here are the places that needs them.

Chimney flashing

On pitched roofs, the high side of the chimney is the most vulnerable to water seepage compared to the sides and the low side.

Flashing installed on the high side is called head flashing while installations on the low side is called apron flashing.

They should installed with a height of at least 6 inches to protect from splashing water.

For large chimneys with very wide widths, saddles should be used to divert water around the chimney.

It must be noted that the lower a chimney is located on a roof, the more prone it would be to water leaks.

Drip edge flashing

This is required at the lower edge of sloped roofs to protect fascia and roof sheathing from water

Flat and sloped roof jointing points

Not all roofs are either flat or sloped. They can be a combination of both as well.

In fact, these are getting more popular with home owners who have a lot a freedom in designing the own house.

When the flat roof as on a more elevated position compared to the sloped roof, the flashing of the sloped roof extends onto the flat one.

And when the flat roof is below the sloped one, flashing is applied on the flat one and extend upwards to the slope.

Gravel stop flashing

The gravel stop prevents material on the roof from falling off and also serves as a shield to protect the roof from damage.

Gravel stop flashing helps protect the fascia from water damage just like the drip edge.

Hip and ridge flashing

This refers to flashing being fixed on the ridge and hip area of pitched roofs.

Sometimes flexible shingles are used as they do a fairly good job and also helps to blend into the roof aesthetics as well.

Other times, metal is the material of choice. But additional layer of shingles are used to cover them up.

Parapet wall flashing

A parapet wall is formed when an exterior wall protrudes and extends above the roof line.

Other than a regular flashing, a cap flashing should also be used for added measure.

Continuous flashing can be used then a vertical wall meets a sloped roof.

Penetration flashing

When a fixture of the house penetrates the roof, it goes without saying that water entry points should be a cause for concern.

These can often be a result of exhaust flutes, plumbing stacks, electrical masts, etc.

In this scenario, rubber flashing or metal are often used.

Sheet metal pan is also a popular choice on flat asphalt roofs.

Roof to wall flashing

When a roof meets a wall, special flashing might be required depending on the roof material and overall configuration.

L-shaped flashing is often used to cover the top of the roofing material and upwards along the bottom of the wall.

Roof vent flashing

For roof vents, flashing basically slides below the shingles.

It overlaps the roofing material on the downhill side resulting an an exposed flashing.

Skylight flashing

Skylights are typically flashed the same way as chimney flashing.

Valley flashing

Roof valleys are one of the most vulnerable areas that are prone to water seepage. It is a very common entry point of the source of water causing damage to a house.

It is therefore paramount to install property flashing in valleys if you intend to maintain a healthy house.

Roof valleys refer to the joining points where two or more segments of the roof orientated in different directions join up.

They are usually perpendicular aligned.

As pitched roofs slope downwards, this effectively creates a valley on the roof.

When watertight metal flashing is used, they are usually at least 24 inches wide.

When flashing is observable, it is called an open valley. And when they are not visible, usually due to it being covered with shingles, it is called a closed valley.

Common problems of roof flashings

As expected, there will always be problems with flashings.

However do note that they are just one category of common roof problems.

The primary reason why roofs leak is not due to deterioration of roofing materials. But with bad workmanship and poor installation of roof flashing.

Some reasons include:

  • Inadequate fastening
  • Inadequate length and height
  • Inadequate sealing
  • Missing or defective components
  • etc

This is why sometimes, a roof continues to leak even though re-roofing has taken place.

Flashing should therefore be replaced when re-roofing. It is more economical than having it done within the natural lifetime of a roof.