Roof Flashing Guide: What It Is, Where It Goes, and How to Choose
What is a flashing on a roof?
Roof flashing is a shaped piece of material used on a roof to seal junctions and edges where leaks can start. In simple terms, roof flashing helps direct water away from openings and joins so the roof sheds rain properly. Without the right detail, moisture can enter through gaps, leading to water penetration and water damage inside the roof structure and ceilings.
Australia’s diverse climate, including heavy rain and occasional storms, increases the risk of internal damage to a home, making the correct choice and fitment of roof flashing especially important.
Why roof flashing matters
A roof has multiple junctions where water can track in. The right roof flashing helps prevent water from entering at these points and reduces the chance of a recurring roof leak. When those junctions are sealed properly, the roof remains more watertight, the building envelope stays protected, and long-term performance improves.
Where roof flashing is commonly used
Most roof flashing is placed where the roof changes direction or meets something else, including:
-
Roof valleys (valley junctions)
-
At walls where the roof meets a vertical surface
-
Around chimneys, skylights, and vents
-
Along edges such as barge capping and drip edge details
If you’re dealing with step details, counter details, or pipe/flue penetrations, these are often best handled as made-to-measure pieces so the junction is sealed neatly and reliably.
Types of roof flashing (profiles people commonly use)
Choosing the right profile is essential for keeping a roof watertight and protecting a building from long-term issues. Common profiles include:
-
Apron flashing – used where a roof meets a wall line or transition
-
Valley flashing – guides runoff through valleys
-
Ridge capping – covers the peak junction where two planes meet
-
Parapet capping – finishes parapet tops and helps shield exposed edges
-
Z flashing – commonly used behind cladding or as a transition to shed water cleanly
-
Window flashing – used at window and cladding junctions to reduce water entry risk
These profiles protect vulnerable junctions and reduce the chance of premature replacement.
Materials: steel, copper, and compatibility (including COLORBOND® & ZINCALUME®)
There are many materials used for roof flashing, including coated steel, and copper. In Victoria, some heritage or specialist work still uses copper; however, most modern projects choose coated steel for strength, value, and consistent finish.
If you’re matching to a pre-finished system, you’ll typically choose:
-
colorbond in a matching finish (with many Colorbond colours available), or
-
Zincalume for a clean metallic look.
If you’re selecting coated steel options, choosing compatible materials helps avoid corrosion risk and reduces issues like early rust in harsh environments. Many customers also prefer specifying BlueScope Steel products for confidence in consistency across the broader roof system.
Tile and metal roof applications
The same weatherproofing principles apply across many roof types, including tile roof flashing details and metal roof flashing details. The goal is always the same: guide rain outward and downward, seal junctions cleanly, and choose a profile suitable for the roof design and exposure.
Made to order: custom work and accurate sizing
For unusual junctions, non-standard returns, or complex penetrations, made to order are often the cleanest solution. This is where custom made flashings are useful—made to your measurements so they fit the detail neatly.
To order accurately, you’ll typically provide:
-
overall dimensions (leg sizes/returns and length)
-
the required thickness (often referenced as BMT)
-
finish/material selection and quantity
If you’re unsure about the best profile for your junction, it’s worth confirming the detail before ordering so the piece is made correctly the first time.
Repair and upkeep
Small repair jobs may be possible if the issue is obvious and safe to access (for example, a lifted edge or minor damage). However, because they are critical to preventing water penetration, repeated leaks or uncertain work should be assessed properly to avoid ongoing internal damage and rework. Basic upkeep checks after storms can also help spot early issues before they escalate.
What are the standards for roof flashing in Australia?
In Australia, they should be selected and fitted in line with the roof system guidance and generally accepted building requirements for weatherproofing. Correct installation matters just as much as the material—poor overlaps and fixings can allow water to track behind the system. The practical rule is simple: choose compatible materials, use the correct box gutter profile, and ensure junctions are sealed so the roof remains watertight and built for long-term protection.
