Most leaks look the same from inside: water coming through the ceiling. But they are not the same problem, and they do not have the same fix. Getting the diagnosis right is most of the job.

Water dripping inside during heavy rain

What it means. Rain-driven water is getting past the roof covering and running down the underside of the roof to a low point, where it drips. The drip is rarely directly below the hole — water follows the structure.

Why it only happens in heavy rain. Light rain is absorbed or evaporates before it gets far. A downpour overwhelms the same gap, and wind-driven rain pushes water sideways into places it would not normally reach. A leak that only appears in a storm usually means a small opening in an exposed position, not a big hole.

What to check. Whether it is always in the same spot or wanders. Whether it started after a storm, after some roof work, or gradually. Any of those narrows the cause considerably.

What fixes it. Depends entirely on the source — tile replacement, flashing renewal, or resealing fixings. Anyone who quotes before finding the source is guessing.

Brown or yellow stains on the ceiling

What it means. Water has been getting in for a while. The stain is dried minerals and dirt left behind as water soaked into the plasterboard or plaster and evaporated. A stain that is spreading or darkening is active. A stain that has stopped growing may be an old leak that was fixed.

The test. Press a fingertip gently against it. Soft, spongy, or crumbly means the board has taken water and will need replacing, not just repainting. Painting over a stained ceiling without fixing the leak is the most common expensive mistake we hear about — it comes straight back, and by then the board above it is worse.

What fixes it. Fix the roof first, let the area dry properly, then repair the ceiling. If the stain keeps returning after the ceiling has been repainted, the roof repair did not address the real source.

Metal deck roof leaks

What it means. On metal deck (zinc or colour-coated steel) roofs, water almost never gets through the sheet itself. It gets in at the fixings and the overlaps.

The usual culprits. The rubber washer under each screw perishes in the sun and stops sealing. Screws work loose with thermal movement. Sheets expand and contract through the day, and the overlap sealant between them eventually fails. Where a sheet has been walked on or bent, water can pool and find the seam.

How it shows up. A line of drips rather than a single point, often following the ribs of the sheet. Drips that start a few minutes into rain rather than immediately. Water appearing at a wall junction rather than mid-ceiling.

What fixes it. Replacing the perished washers and reseating or replacing the screws is the correct fix for fixing-related leaks; simply smearing sealant over the screw heads is a short-term patch that fails within one or two seasons. Overlap leaks need the sheets properly sealed, not coated from above. A specialist coating system can extend the life of a metal roof, but it is not a substitute for fixing loose fixings.

Flat concrete roof and waterproofing

What it means. A flat concrete roof has no slope to shed water quickly, so it depends entirely on a waterproofing membrane on top of the slab. Water sits on it, and any failure in that membrane becomes a leak into the space below.

Why it fails. UV exposure hardens and cracks the membrane. Ponding water — where the slab does not drain properly — accelerates it. Blisters form where water gets under the membrane. Edges and upstands, where the membrane turns up to meet a wall, are the most common failure points. Roots from plants and heavy foot traffic do damage too.

The honest version. Patching a failed flat roof membrane is usually temporary. If the membrane has passed its life across the roof, the correct repair is stripping and renewing it. That is the expensive answer, and it is often the true one. A contractor who proposes patching should be able to explain why the rest of the membrane is still sound.

What good work looks like. Surface cleaned and prepared properly, not just swept. Primer applied. Membrane laid with correct overlap and properly turned up at edges and upstands. Drainage falls checked so water actually leaves the roof. A protective layer on top if the roof is walked on.

Gutters and downpipes

What it means. Often not a roof leak at all. When a gutter is blocked, water backs up under the lowest row of tiles or under the roof edge, and runs down the outside wall. It reads as a roof problem but the roof is fine.

How to tell them apart. A gutter problem usually shows water on the wall or at the fascia rather than a ceiling stain well inside the house. It gets worse during sustained rain rather than in bursts. Look at the gutter during rain if you safely can — if it is overflowing while the roof above looks intact, the gutter is your answer.

What fixes it. Clear the debris. Then check the joints and the fall — a gutter that has sagged holds water and will always leak. Replace rusted or split runs and check that the downpipe actually discharges away from the house, not against the wall.

Prevention. Clear gutters before the monsoon season rather than after the first leak. It is the cheapest maintenance there is, and it prevents the most expensive kind of water damage — the slow kind that rots fascia boards and eaves.

What to do in the first hour of a leak

Before a contractor can get to you, these steps limit the damage without any risk:

1. Contain, do not stop. Put a bucket or basin under the drip and a towel around it. Do not try to plug the leak or climb up.
2. Protect what is underneath. Move furniture, electronics, and anything fabric out from under the drip. Water spreads sideways along a ceiling and comes down where you least expect it.
3. Kill the power to that area if water is near electrics. If water is anywhere near a light fitting, socket, or switch, switch that circuit off at the breaker. Do not touch a wet fitting.
4. Photograph everything. The drip, the stain, the ceiling, anything damaged. It helps the contractor and it helps if you claim on insurance.
5. Put a container under it and leave it. Note roughly how fast it fills — that tells a contractor how urgent the job is.
6. Do not climb on the roof. Not in the rain, not on a metal deck, not “just to have a look”. This is the one piece of advice on this page we would repeat.