Flashing seals every joint, penetration, and junction on your roof. When it fails, water gets in. Here's what you need to know.
Roof flashing is thin metal (typically Colorbond, lead, or zinc) shaped and installed at every point where the roof surface meets another surface or is penetrated. Its sole purpose is to direct water away from joints and prevent it entering the building.
**Common flashing locations:** • Where the roof meets a wall (step flashing, apron flashing) • Around chimneys and flues • Around plumbing vent pipes • Around skylights • At roof valleys (valley flashing) • Where roof pitch changes • Around air conditioning units on the roof • At parapet walls on flat roofs • Around solar panel mounting points
Every penetration and junction on your roof has flashing — and every piece of flashing is a potential leak point if it fails. On a typical home, there may be 15–30 individual flashing points, each requiring correct installation and ongoing integrity.
Flashing failures are one of the most common causes of roof leaks. They occur because:
**Corrosion:** Older galvanised flashing corrodes over time, particularly in coastal areas. Salt air, pooling water, and contact with dissimilar metals (galvanic corrosion) all accelerate deterioration.
**Sealant breakdown:** Many flashing installations rely on silicone or polyurethane sealant to complete the waterproof seal. These sealants have a 10–15 year lifespan before UV degradation causes them to crack and shrink.
**Thermal movement:** Metal flashing expands and contracts with temperature changes. Over years of cycling, fixings loosen and overlaps open up.
**Poor original installation:** Flashing that was incorrectly sized, inadequately overlapped, or improperly sealed at installation will fail prematurely. This is unfortunately common in budget roofing work.
**Building movement:** Houses settle and move over time. Flashing at wall-to-roof junctions can be stressed by differential movement between the roof structure and masonry walls.
**Storm damage:** High winds can lift flashing edges, and hail can dent or puncture thin flashing material.
Flashing leaks often present as mysterious water ingress that's difficult to locate:
• Water stains on walls near the roofline (especially where roof meets wall) • Damp patches that appear only during heavy rain or wind-driven rain • Water stains around skylights or roof penetrations • Rust stains running down walls from above • Mould growth on interior walls near the ceiling • Drips in the roof space that don't correspond to obvious tile or sheet damage
**The wind-driven rain test:** Many flashing leaks only appear during rain with wind from a specific direction. This is because wind pressure forces water uphill and into gaps that gravity alone would not reach. If you notice leaks only during certain storms, flashing is the likely culprit.
We use systematic leak investigation — starting inside the roof space and tracing water paths back to their entry point — to identify exactly which flashing has failed.
The repair approach depends on the type and extent of failure:
**Re-sealing (minor):** If the flashing metal is sound but sealant has failed, removing old sealant and applying new roofing-grade sealant can restore the waterproof seal. Cost: $150–$400 per location.
**Partial replacement:** If one section of flashing is corroded or damaged, it can be replaced without disturbing the entire run. The new section must overlap the existing flashing by at least 150mm. Cost: $300–$800 per location.
**Full replacement:** If flashing is extensively corroded or was poorly installed originally, full replacement provides the most reliable long-term solution. Cost: $500–$2,000+ per location depending on complexity.
**Materials used:** • Colorbond flashing — standard for most residential work, colour-matched to roof • Lead flashing — used for complex shapes (chimneys, curved surfaces) due to its malleability • Zinc/aluminium — used where flashing is concealed (under tiles)
All our flashing work is installed to AS 1562.1 with minimum overlaps, correct fixings, and appropriate sealants for the application.
Proactive maintenance prevents most flashing failures:
**Annual inspection points:** • Check visible flashing for rust, lifting edges, or cracked sealant • Look for staining on walls below flashing locations • After storms, check that no flashing has been lifted or displaced • Inspect around skylights for sealant deterioration • Check plumbing vent flashings (rubber boots degrade in UV)
**Key prevention strategies:** • Replace rubber boot flashings (around vent pipes) every 10–15 years — they crack in UV before the roof itself needs attention • Re-seal silicone joints every 10 years as preventative maintenance • Keep debris clear of flashing areas — trapped moisture accelerates corrosion • When re-roofing, replace all flashing regardless of apparent condition • Use compatible metals — never install steel flashing against copper pipes (galvanic corrosion)
We include flashing inspection as part of every roof maintenance visit. Catching a $200 re-seal before it becomes a $2,000 water damage repair is exactly what preventative maintenance is for.
Colorbond and lead flashing typically lasts 30–50+ years. Galvanised flashing lasts 20–35 years. Sealants used with flashing last 10–15 years and need periodic renewal. Rubber boot flashings around vent pipes last 10–15 years before UV degradation causes cracking.
Absolutely. Flashing repairs are targeted work — we access the specific failure point, repair or replace that section, and re-seal. Most flashing repairs take 1–3 hours and don't require disturbing the surrounding roof surface.
This is a classic sign of flashing failure. Normal rain runs straight down and is handled by the roof surface. Heavy or wind-driven rain forces water sideways and uphill into gaps that flashing should seal. Failed sealant or lifted flashing edges allow water in only under these conditions.
That's a Dektite or pipe flashing boot — a rubber collar that seals around plumbing vent pipes penetrating the roof. They're made of EPDM rubber and have a 10–15 year lifespan before UV causes cracking. They're one of the most common (and cheapest) leak sources on older roofs.
Suspect a Flashing Leak?
We systematically locate and repair flashing failures. Same-week appointments across the Central Coast, Sydney, and Newcastle.