Start at the stain, think uphill
Water enters the roof, runs down the underside of the tiles or sheet, along the sarking or a batten, and drops off at a nail, a joint or a sag. The drip point is almost always downhill of the entry point — sometimes by a couple of metres. So: find the stain, work out which way the roof slopes above it, and look uphill.
1. Read the ceiling
- A round stain that grows after rain — a single entry point, active.
- A stain along a line — water is tracking along a batten or a beam. Look where that line meets an outside wall or a ridge.
- Stains near an outside wall, top of the wall wet — probably a gutter overflow or a fascia problem, not the roof surface.
- Stain under where the aircond pipe goes out — the pipe flashing. Number one cause in the Klang Valley.
- Damp patch that never quite dries, white salt deposits — a flat concrete slab above with failed waterproofing.
2. Get into the roof space
If you have a ceiling access hatch, go up with a torch in daylight. Look for daylight through the roof (pinholes in zinc show as stars), water stains on the underside of the sarking, damp or dark timber, and the tell-tale drip trail. Follow any staining uphill to where it starts.
3. The hose test
With someone inside watching, run a garden hose on the roof for a few minutes at a time, starting low and moving uphill in bands, one section at a time. When the drip appears inside, the leak is in the band you're wetting — not above it. This is how roofers find awkward leaks; it works for homeowners too, but only from a ladder on a single-storey roof you can reach safely. Don't walk on a tile roof.
4. The six usual places
- Pipe and vent flashings — aircond pipes, water heater, aerials, solar brackets.
- Ridge and hip caps — cracked mortar bedding.
- Valleys — rust, blockage, undersized.
- Party-wall and parapet flashing — cracked cement fillet where the roof meets a wall.
- Cracked or slipped tiles / loose screws on metal deck — often where someone has walked.
- Gutters — blocked, sagging, or too small. Half of monsoon "roof leaks".
When to stop and call
If the roof is double-storey, steep, wet, or tiled; if you can't see the entry point from the roof space; if the leak is into an electrical fitting; or if it's been patched before and come back — that's a roofer's job. An inspection with photos costs RM150–300 in the Klang Valley and is credited against the repair. Roof leak repair explains what a proper fix involves, and the cost guide what to expect to pay.