Roofs: tiles, metal and where leaks really start
Most roof leaks start at the junctions, not in the middle of the tiles or sheets: valleys, ridge and hip capping, flashings at walls and chimneys, penetrations such as flues and vents, and box gutters. Identify the material first, whether terracotta or concrete tiles, metal sheet, slate or older asbestos-cement sheeting, then look from the ground and, where safe, the roof space for slipped or cracked tiles, failed ridge pointing, rust at laps and fixings, and water stains on timbers. A restoration that cleans, repoints and coats a tiled roof treats surface wear; it does not fix a failing valley, flashing or sagging frame.
- 01CoveringTiles, sheet or slate shed most of the rain
- 02JunctionsValleys, ridges, flashings and penetrations are where leaks begin
- 03DrainageGutters, box gutters and downpipes carry it away, or back inside
A coating refreshes a surface. It does not fix a valley.
Start by identifying the roof
The material sets the questions. A roof can also be mixed: a tiled original house with a metal-roofed extension, or a slate front with later sheeting at the rear. Record each section separately.
| Material | Where you find it | How to recognise it | What usually needs attention |
|---|---|---|---|
| Terracotta tiles | Much pre-war and many later homes | Fired clay, colour through the tile, often orange or red; glazed versions exist | Ridge and hip bedding and pointing, cracked or slipped tiles, valleys |
| Concrete tiles | Very common from the post-war decades onward | Thicker, heavier tiles with a surface coating that wears to expose a sandy texture | Surface wear, pointing, cracked tiles and valleys |
| Metal sheet | All eras; older galvanised iron, later coated steel | Corrugated or trimdeck profiles, fixed with screws or nails through the sheet | Rust at laps, fixings and gutters, incompatible metals, low-pitch drainage, condensation |
| Slate | Period homes | Thin natural stone, often blue-grey, fixed with nails | Slipped or cracked slates and corroded fixing nails; specialist repair |
| Asbestos-cement sheeting | Homes, sheds and carports built or altered before 1990 | Grey fibre-cement corrugated sheets, often weathered with lichen | Do not walk on, drill, cut or water-blast; testing and specialist advice first |
The Asbestos and Silica Safety and Eradication Agency advises that homes built or renovated before 1990 may contain asbestos, and only testing confirms it. Weathered asbestos-cement roofing is brittle as well as hazardous, so nobody should walk on it.
Where roofs actually leak
| Location | What goes wrong | Signs inside or below |
|---|---|---|
| Valleys | Debris blocks the valley iron, water backs up under the tiles, or the valley iron corrodes | Stains on ceilings near internal corners of the roof |
| Ridge and hip capping | Bedding cracks and pointing fails, letting wind-driven rain in | Damp spots along the line of the ridge after storms |
| Flashings at walls, chimneys and skylights | Flashings lift, crack, corrode or were never properly installed | Stains where the roof meets a wall or around a chimney breast |
| Penetrations | Seals around flues, vents, aerials and air-conditioning fail | Localised stains below the penetration |
| Box gutters and parapets | Internal gutters overflow into the building when blocked or undersized | Sudden heavy leaks in storms, often well inside the house |
| Eaves gutters | Blocked or sagging gutters overflow back into the eaves and wall | Stained eaves linings, damp walls below, overflow during rain |
QBCC's maintenance guide notes that many roof leak complaints turn out to be maintenance rather than defective work, and lists the basics: keep leaves out of gutters and downpipes, clean valley gutters regularly, and repair cracked or broken tiles, guttering and flashings promptly.
Metal roofs: fixings, laps and incompatible metals
Coated steel roofs usually fail at the details rather than across the sheet: corroded fixings, laps where water sits, cut edges, and anywhere debris holds moisture. One cause is often missed: some metals accelerate corrosion of coated steel. BlueScope's Lysaght compatibility bulletin lists copper and lead as incompatible with ZINCALUME® and COLORBOND® steel, both in direct contact and where water drains from one onto the other. Look for copper hot-water or air-conditioning pipes discharging onto a steel roof, and old lead flashings left in place when a roof was renewed.
Under a metal roof, condensation can form on the underside of the sheet on cold nights and drip into the roof space. Look for drip marks on insulation or ceilings in a pattern rather than at one point. Newer homes are subject to the condensation provisions introduced with NCC 2022; older roofs may have no insulation blanket or sarking under the sheet.
What the roof space can tell you
Only enter a roof space where it is safe: good lighting, solid footing on joists, no exposed wiring, and no suspicion of asbestos-containing material. From the access hatch you can often see enough.
| Look for | What it can mean |
|---|---|
| Daylight through tiles or at the ridge | Gaps that can let in wind-driven rain; normal in small amounts under some unsarked tile roofs |
| Water stains or tide marks on rafters, battens or sarking | Past or present leaks; note the location against the roof above |
| Damp, compressed or stained insulation | An active or recent leak, or condensation |
| Rusted nails and fixings | Persistent moisture or condensation |
| Sagging, cracked or altered rafters and purlins | Overloading, decay, removed supports or a heavier roof covering added later |
| Exhaust fans venting into the roof space | Moisture being pumped into the roof, which can cause condensation and mould |
Repair, restoration or replacement
These are three different jobs, and quotes often blur them. A repair fixes a defined defect, such as a valley iron, a flashing or a set of cracked tiles. A restoration on a tiled roof usually means cleaning, replacing broken tiles, re-bedding and re-pointing ridges and hips, and often a coating. A replacement renews the covering, and sometimes the battens, sarking and flashings.
Ask every quote to name the sections of roof covered, what happens to valleys and flashings, whether battens and sarking are inspected, and what the coating actually does. A coating can refresh the surface of worn concrete tiles; it does not repair a corroded valley, a failed flashing or a sagging frame. On metal roofs, overpainting is a specialist system with its own preparation requirements, not a cure for corroded sheets.
Common misreads
| What people say | What is closer to right |
|---|---|
| "No stains on the ceiling, so the roof is fine" | Water can run along timbers and sarking before showing, and insulation can absorb it. Check the roof space. |
| "The roof was restored, so it is as good as new" | A restoration treats surface wear. Ask what happened to valleys, flashings, battens and sarking. |
| "Leaks come through broken tiles" | Most leaks start at junctions: valleys, ridges, flashings, penetrations and box gutters. |
| "A metal roof will last forever" | Fixings, laps, cut edges and incompatible metals can corrode long before the sheet itself. |
| "The gutters were cleaned, so overflow is solved" | Overflow can also come from undersized gutters, poor falls, blocked downpipes or missing overflow provisions. |
What to ask before you buy
Ask for invoices for any roof work with a defined scope and roof sections, as set out in keeping a record of your home. A standard building inspection usually excludes the adequacy of roof drainage and concealed roof areas, so read the report's limitations, covered in inspection before auction. For older homes, the era guides show which roof materials to expect: pre-1920s, interwar and post-war.
Worked example: a restored roof and a new ceiling stain
Illustrative reasoning example, not an inspected property. A 1960s concrete-tile roof was "restored" two years ago: cleaned, ridges re-pointed and coated. A new stain appears near an internal corner after a storm. The invoice lists ridge work and coating, but says nothing about the valley.
The stain sits below a valley, and the restoration scope did not include it. The next step is a roof plumber to inspect the valley iron and the tiles alongside it, not another coating. If the valley iron is corroded or debris has been backing water under the tiles, the repair is local and defined. Record the outcome against the right section of roof.
Frequently asked questions
Where do most roof leaks start?
At junctions rather than in the middle of the tiles or sheets: valleys, ridge and hip capping, flashings at walls and chimneys, penetrations such as flues and vents, and box gutters.
How can I tell terracotta from concrete roof tiles?
Terracotta is fired clay with its colour right through, often orange or red. Concrete tiles are thicker and heavier, with a surface coating that wears to expose a sandy texture.
Is a roof restoration the same as a new roof?
No. A tiled-roof restoration usually means cleaning, replacing broken tiles, re-pointing ridges and coating. It treats surface wear but does not fix corroded valleys, failed flashings or a sagging frame unless those are in the scope.
Can copper pipes damage a Colorbond or Zincalume roof?
Yes. BlueScope advises that copper and lead should not contact ZINCALUME® or COLORBOND® steel and that water from copper pipes should not run onto it, because it accelerates corrosion.
Could my old roof contain asbestos?
If the home or shed was built or altered before 1990, grey fibre-cement roof sheeting may contain asbestos. Only testing confirms it. Do not walk on, drill, cut or water-blast it.
What should I look for in the roof space?
Water stains on timbers or sarking, damp or compressed insulation, rusted fixings, sagging or altered framing, daylight at the ridge and exhaust fans venting into the roof. Only enter where it is safe.
Why does my metal roof drip on cold nights?
Likely condensation forming on the underside of the sheet. Older metal roofs may lack an insulation blanket or sarking. Look for drip marks in a pattern rather than at a single point.
Does a building inspection check the roof properly?
A standard inspection looks at safely accessible roof areas, but commonly excludes the adequacy of roof drainage and concealed sections. Read the limitations and get a roof plumber for specific concerns.
How this guide was researched
We identify the roof material, follow water to the junctions where it most often enters, then separate repair, restoration and replacement scopes, with a fictional example.
Limits: Roof access is hazardous. Material identification from the ground is indicative; asbestos and concealed defects need testing and safe professional access.
Sources
- Your essential home maintenance guideQueensland Building and Construction Commission · accessed
- Product advisory bulletin PAB02: metal and timber compatibilityLysaght (BlueScope) · accessed
- Asbestos in the homeAsbestos and Silica Safety and Eradication Agency · accessed
- Overview of changes to energy efficiency and condensation in NCC 2022Australian Building Codes Board · accessed
- Repairs and maintenanceYourHome, Australian Government · accessed
- AS 4349.1-2007 Inspection of buildings, Part 1: Pre-purchase inspections, residential buildingsStandards Australia · accessed