Colorbond flashing is pre-painted steel folded into trims that seal the joins, edges and penetrations of a roof so water cannot get under the sheeting. Supply and fitting usually cost about $30–$90 per lineal metre in Sydney, with leak-prone areas such as valleys and walls costing more (indicative — get itemised quotes).
This guide covers the main roof flashing types, sizes, costs, foam closure strips and the install rules that decide whether a join stays dry.
Key points
- Most leaks start at flashings, not at the sheets, so the flashing type, lap and fixing matter more than the colour.
- Colorbond flashing suits Colorbond and most steel roofs, while aluminium and lead suit special details, as long as dissimilar metals do not touch.
- Valleys, walls and pipe penetrations cost more per metre than plain barge or ridge trims because they take more labour (indicative — get itemised quotes).
- Foam closure strips and sealant are cheap parts that fail first, so replace them whenever you replace the flashing.
What is colorbond flashing?
Flashing is a thin metal trim that bridges a gap or a joint, and its job is to move water onto the roof surface and away from the building. Colorbond is the prefinished steel most Australian roofers use because the colour matches the sheets, gutters and fascia.
| Term | What it means | Why it matters |
|---|---|---|
| Colorbond flashing | Pre-painted steel trim folded to suit a roof join | Matches the roof colour and lasts as long as the sheeting |
| Metal flashing | Any sheet metal trim, including steel, aluminium, copper or lead | Choose a metal that suits the roof and doesn’t corrode against it |
| Underflashing | Flashing hidden below the roof covering | Catches water that gets past the visible flashing |
| Fascia capping / facia capping | Trim that covers the fascia board’s top and face | Protects timber from rain and UV, and hides the gutter bracket |
| Parapet | Wall that rises above the roof edge (often spelled “parrapet”) | Needs a capping and a back flashing to stay dry |
- Folded on site or ordered: a roofer can fold plain trims on site, while complex shapes are ordered from a roll former to suit the profile.
- Same-colour match: pick the Colorbond colour to match the sheets, because a mismatch shows from the street.
- Compatibility: keep copper and lead from draining across Colorbond, since the runoff can stain or corrode the coating.
Types of colorbond flashing
Learning the roof flashing types helps you read a quote, because each type has its own price and its own failure points.
| Type | Best for | Where leaks start | Price band |
|---|---|---|---|
| Barge capping | Gable ends and roof edges | Loose fixings and missing sealant | $ (indicative — get itemised quotes) |
| Ridge capping | Ridge and hip lines | Failed foam, cracked mortar on tile roofs | $ (indicative — get itemised quotes) |
| Apron flashing | Where a roof meets a wall at the top of a slope | Gaps behind the wall cladding | $$ (indicative — get itemised quotes) |
| Step flashing | Where a roof meets a wall along a slope | Wrong lap or rusted steps | $$ (indicative — get itemised quotes) |
| Valley flashing | Where two roof planes meet | Rust-through, debris build-up | $$$ (indicative — get itemised quotes) |
| Parapet capping | Walls rising above the roof | Open joints in the capping | $$$ (indicative — get itemised quotes) |
Colorbond roof flashing
The standard choice for steel roofs, covered in detail in our Colorbond flashing guide.
Aluminium flashing
Used for details where steel would rust, explained in the aluminium flashing guide.
Ridge, colorbond ridge and barge capping
- Ridge capping: see our ridge capping guide for tile and metal ridge details.
- Colorbond ridge capping: the Colorbond ridge capping guide covers profiles and fixings.
- Barge capping: read the barge capping guide for gable-end details.
Colorbond flashing sizes and fascia capping
Flashing sizes depend on the roof profile, the wall and the water load, so measure the job before ordering any trims.
| Flashing | Typical size | Notes |
|---|---|---|
| Barge or ridge trims | Girth sized to the profile (indicative — check the manufacturer’s data sheet) | Must cover the sheet ends and ribs fully |
| Wall flashing | Cover turned into the wall, often 150 mm or more (indicative — check the manufacturer’s data sheet) | Cut into the brick or cladding, not just stuck on |
| Valley gutter | Width and depth set by roof area (indicative — get itemised quotes) | Bigger roofs need a wider, deeper valley |
| Fascia capping | Fits the fascia board’s height and depth (indicative — get itemised quotes) | Check for rot under old paint before capping |
| Facia capping on a flat roof | Matched to the roof’s edge detail (indicative — get itemised quotes) | Needs a drip edge to stop water tracking back |
| Colourbond flashings, custom | Made to order from a drawing (indicative — get itemised quotes) | Send the roofer photos and measurements |
Colorbond flashing cost and roof valley replacement cost
The material is cheap, but the labour, safety gear and roof access make up most of a flashing bill.
| Item | Typical price (AUD, Oct 2026) | Notes |
|---|---|---|
| Colorbond barge or ridge trim, materials only | $10–$30 per lineal metre (indicative — get itemised quotes) | Price depends on girth and colour |
| Flashing, supplied and installed | $30–$90 per lineal metre (indicative — get itemised quotes) | Includes fixings, sealant and foam |
| Roof valley replacement cost | $100–$250 per lineal metre (indicative — get itemised quotes) | Includes lifting sheets or tiles beside the valley |
| Penetration flashing (pipe or vent) | $120–$350 each (indicative — get itemised quotes) | Varies with size and roof type |
| Full flashing replacement on a typical house | Several thousand dollars (indicative — get itemised quotes) | Depends on the number of walls and valleys |
- Roof height: two-storey homes need scaffold or edge protection, which adds to the labour line.
- Roof type: tile roofs take longer because tiles must be lifted, cut and relaid beside the flashing.
- Rust damage: rotted battens or fascia under old flashing add repair work before the new trim goes on.
- Access: narrow side access and steep blocks increase handling time and risk.
- Metal choice: aluminium, copper and lead cost more than steel, and special shapes cost more than standard folds.
- Bundled work: doing flashings during a re-roof or restoration costs less than a separate visit.
Colorbond flashing pros and cons
| Pros | Cons |
|---|---|
| Colour-matched to Colorbond sheets and gutters | Cut edges can rust if scratches aren’t treated |
| Strong, lightweight and easy to fold on site | Reacts with copper and lead run-off |
| Wide range of standard trims off the shelf | Complex shapes need custom folding and lead time |
| Long life when fixed and sealed correctly | Sealants and foam still age and need checking |
| Fits most steel roof profiles | Not ideal for coastal sites without correct grade |
How to choose colorbond flashing
- Identify the join: wall, valley, ridge, barge or pipe, because the shape of colorbond flashing changes with each.
- Match the roof metal: use Colorbond for Colorbond roofs, and avoid mixing copper or lead where water runs over the steel.
- Check the exposure: coastal Sydney sites need the right coating grade and regular washing of covered areas.
- Measure the profile: note the sheet profile so foam strips and end caps fit the ribs.
- Choose the colour: match the roof, or contrast on trims as long as it’s consistent around the house.
- Plan the water path: follow where the water runs from the flashing into the gutter or valley before you buy.
Colorbond flashing installation essentials
- Remove failed trims and clean out old sealant, dirt and rust from the roof surface and wall.
- Check the underflashing and the battens beneath it; replace rotten timber before you fix new metal.
- Lap upslope pieces over downslope pieces, so water runs onto the next sheet and never into the join.
- Fit corrugated foam infill strips or foam closure strips for metal roofing at the ridge and eaves, to block wind-driven rain and pests.
- Fix with the right screws through the crest of the sheet with sealing washers, and keep fixings in line.
- Seal the laps with a roofing sealant that suits the metal, and read the product label before use.
- Check for debris in valleys and behind walls after the job, then test with a hose from the top down.
Wall, parapet and fence flashing
- Corrugated wall flashing: a corrugated wall needs profile-matched flashing and foam infill so rain can’t blow up behind it.
- Wall-to-roof joins: chase the flashing into the brick or fit it behind the cladding, not just face-fixed with sealant.
- Parapet capping: a parapet needs a sloped capping with drip edges on both sides, plus a back flashing behind it.
- Fence flashing: where a fence meets the house wall, a small cover flashing stops water getting behind cladding.
- Roof capping cement: older tile ridges use cement bedding, and our general flashing guide explains why flexible systems often replace it.
- Cladding joins: check the manufacturer’s detail for your cladding, because the flashing must match the system.
Decktites and pipe flashing
- Decktites: a flexible rubber boot on a metal base that seals round pipes, vents and flues on metal roofs.
- Sizing: choose the boot to suit the pipe diameter, since a loose fit lets water run down the pipe.
- UV ageing: rubber boots perish with age, so check them at least once a year.
- Lead strip: soft lead strip moulds to odd shapes, but lead work needs care and it must not drain onto Colorbond.
- Flues and hot pipes: keep flashing a safe distance from hot flues and use rated flue flashings only.
- Gas, electrical and plumbing: for pipework, book a licensed plumber or gasfitter rather than touching the connection.
Metal flashing: Colorbond vs aluminium vs lead
| Metal | Best for | Watch out for |
|---|---|---|
| Colorbond steel | Standard roof trims and gutters | Scratched edges and cut ends |
| Aluminium | Coastal sites and wet areas | Contact with other metals and wet concrete |
| Lead | Complex shapes and heritage details | Handling safety and staining run-off |
| Copper | Heritage and premium details | Run-off staining Colorbond and zinc |
Colorbond flashing FAQs
What is the difference between flashing and capping?
Flashing keeps water out of a gap or joint, while capping covers an exposed edge or ridge. A ridge cap and a barge cap are both flashings in practice, and many roofers use the terms together. Both need laps, fixings and sealant that suit the roof profile.
How long does colorbond flashing last?
Well-fitted colorbond flashing usually lasts as long as the sheeting, but sealants, foam strips and fixings age faster. In coastal Sydney, wash exposed trims and touch up any scratches. Check the flashing at every roof inspection and replace worn sealant promptly (indicative — get itemised quotes).
Can I use aluminium flashing with a Colorbond roof?
Often yes, if the detail is designed for it, but dissimilar metals can corrode where they touch in wet conditions. Ask your roofer to separate them with the right isolation material or choose the same metal throughout. See the aluminium flashing guide for specifics.
How much does roof valley replacement cost?
Valleys are one of the dearer flashing jobs because the roofer has to lift sheets or tiles on both sides. Cost depends on length, roof type and access, and it usually costs more per metre than barge or ridge work (indicative — get itemised quotes).
Do foam closure strips matter on a metal roof?
Yes. Foam closure strips fill the gap between the sheet profile and the flashing, so wind-driven rain, dust and insects can’t get in. They perish with age, so replace them whenever you replace ridge or wall flashings.
Can I replace roof flashing myself?
Flashing work is working at height, and the details around walls and valleys are easy to get wrong. Book a licensed roofer, who will also check for asbestos before disturbing any old fibre-cement sheeting or trims.
Getting colorbond flashing installed in Sydney
Flashing is a small part of the roof budget and a big part of the leak risk. TQN Construct’s licensed roofers fold, fit and seal colorbond flashing to suit your roof profile, and we inspect the underflashing, battens and foam before closing up. You receive an itemised quote that lists each trim and its length. Book a free measure and quote.
