Five clues worth collecting first
When does it leak?
Every time it rains points to a real hole: a rusted sheet, a lifted nail, a cracked tile or a failed flashing. Only in a downpour suggests something overflowing, like spouting, a valley or an internal gutter. Only in one wind, say a southerly or a nor'wester, suggests rain being driven under a lap or flashing on that side. Marks after cold, clear nights with no rain usually mean condensation rather than a leak.
Where is the stain?
Sketch a rough floor plan and mark the stain on it. Then picture the roof above. Is the mark under a chimney, a skylight, an inside corner where two slopes meet, the ridge, or close to an outside wall? The table below shows what each spot tends to mean.
What's changed lately?
Leaks often start a few weeks after someone else has been on the roof. Think about solar panels, a new aerial or satellite dish, a heat pump install, a recent storm, or a tree that's grown out over the house.
What can you see from the ceiling hatch?
On a bright day, open the hatch and look in with a torch from the top of the ladder. Pinpricks of daylight, dark streaks on timber or a damp patch on the insulation can lead you close.
What happens when it really pours?
Next time it buckets down, watch from a window or the porch. Which spouting spills over? Does a valley overflow sideways? Is a downpipe gushing at a joint? Film it, because the roofer will probably visit on a dry day.
What the stain's position usually points to
| Likely cause | What you might spot from the ground | |
|---|---|---|
| Below a chimney or flue | Flashing that's lifted or rusted, or old mortar breaking up | Rust streaks, gaps, or flashing standing away from the brickwork |
| Under an inside corner of the roof | A valley that's blocked, rusted or too narrow for the water it carries | Leaves or moss in the valley, or water spilling sideways in rain |
| Close to an outside wall or above a window | Spouting overflowing back over the fascia | Water pouring over the back edge of the spouting |
| Small spots dotted under an iron roof | Nails that have lifted, or screws with perished washers | Nail heads standing proud, or rust rings around the fixings |
| Around a skylight | Failed flashing or seals around the frame | Stained flashing, or debris piled on the uphill side |
| Under a flat roof, deck or parapet | A split or lifted Butynol seam, or a blocked outlet letting water pond | Water still sitting on the membrane a day after rain |
| Many rooms at once, mostly on cold mornings | Condensation, or a roof failing in lots of places | Often nothing, which is a clue in itself |
Before you open the ceiling hatch
Look from the ladder at the hatch rather than climbing in. Ceiling linings won't hold your weight, and one slip off a joist can put a leg through the ceiling. Keep your hands off wiring, and switch off at the switchboard if water is anywhere near light fittings. WorkSafe says homes built before 1 January 2000 may contain asbestos and that you can't tell by looking, so if you see old sheet material, pipe lagging or anything crumbly, leave it alone and treat it as asbestos until it's tested.
Suspects by roof type
Corrugated iron and longrun. Lifted nails on older roofs, screws whose washers have perished, laps where sheets join, rust along the lower edges and around fixings, and flashings at walls and chimneys. Our guides on roof screws and nails and rusty iron roofs go further.
Decramastic (pressed metal tiles with a stone chip coating). Tiles dented or cracked by foot traffic, rust where the chip has worn away, and lifted tiles along ridges and barges. They're easily damaged by anyone walking on them, one more reason to stay off.
Concrete and clay tiles. Cracked or slipped tiles, ridge caps with crumbling mortar, and valleys clogged with moss and leaves.
Butynol and other membranes. Seams that have lifted, splits from movement, and outlets blocked so water ponds and finds the weakest join. See flat roof repair.
Is it actually the roof?
A fair share of ceiling stains turn out to be plumbing. Older homes may have a hot water header tank in the ceiling space, and pipes, an upstairs shower or a heat pump's drain line can all mark a ceiling. If the stain keeps growing on dry days, call a plumber before a roofer.
Bathroom and kitchen fans are worth checking too. If one blows into the ceiling space instead of outside, the steam settles on the underside of the roof and drips back down.
Water marks on walls of a home built between 1988 and 2004 may not be the roof at all. New Zealand's leaky homes problem centres on timber-framed homes from those years that weren't fully weathertight, often with flat roofs, minimal eaves and complex roof shapes. That calls for a weathertightness specialist or building surveyor as well as a roofer.
How a roofer takes it from here
Your clues get the roofer to the right part of the roof. They'll usually check the ceiling space properly, then the roof above and uphill of the stain, because water runs along underlay, purlins and rafters before it drops. The drip on your ceiling can be some distance from the hole.
If it still won't show itself, a roofer may run a hose over one section at a time while someone watches inside. That needs a person up top with the right gear, so it's never a homeowner test. Our page on roof leak repair covers what happens next, and how to fix a roof leak explains what a lasting repair looks like.
What you can work out, and what you can't
You can
- The timing pattern, from a simple leak diary
- Where the stain sits in relation to chimneys, valleys and walls
- Overflowing spouting or valleys, watched from the ground in heavy rain
- Daylight or wet timber seen from the ceiling hatch with a torch
- Who has worked on the roof recently
Leave to a roofer
- The exact point where water gets in
- Hose testing, one section at a time
- Lifting sheets, tiles or flashings to look underneath
- Moisture meter checks in the ceiling space
- Any roof or ceiling material that might be asbestos
Where we'd start
We'd give it one wet evening and one dry morning. Watch the spouting and valleys while it's pouring, then look in from the ceiling hatch once it's light. Mark the stain on a rough sketch with the chimney, skylights and valleys drawn in, and note when each leak happened. A roofer handed that sketch can head straight for the right spot, and less time searching up top usually means a smaller job. Our leak finder turns your answers into a likely cause.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.