What should you do about a roof leak at a landed home?

Roof leak repair: finding the source

Most roof leaks at landed homes start at a few weak points, and a roofer or a waterproofing specialist fixes them once the source is found. Finding it is the hard part, because water can run along a rafter or the underside of a slab before it drips through the ceiling.

Common entry points to check:

• Clogged gutters and downpipes. Leaves and silt block the flow, so water overflows back under the roof edge.
• Cracked or slipped tiles. One broken or shifted tile lets rain straight onto the layer below.
• Failed flashing. The strips that seal the joint where a roof meets a wall or parapet can crack or lift.
• Worn sealant at skylights. Sealant around skylights and vent pipes hardens and splits with age.
• Ponding on flat roofs. Water that sits after rain works into cracks in the screed or waterproofing.

On a terrace or semi-detached house, a landed roof leak can also come in along the shared wall, so note which side the stain is on. If the ceiling board is soaked or sagging, read ceiling leak: what to do first.

During heavy rain

1. Catch the water. Put buckets under each drip, with a towel inside to cut splashing, and empty them often.
2. Move furniture and electronics. Shift rugs, documents and unplugged electronics away from the drips. If a plugged-in item is wet, leave it and keep away.
3. Switch off any wet light point at the breaker. Do this only if the DB box is dry and away from the leak and you are dry. Otherwise keep away.
4. Note the time and wind direction. Write down when the drip started and the wind direction, to help a roofer trace the entry point.

For a landed home, ask a Licensed Electrical Worker (LEW) to check any light point that got wet. The Energy Market Authority (EMA) says the class of LEW to engage depends on the scale of your electrical installation (EMA guidance on engaging licensed electrical workers).

Why leaks show up in certain months

A roof that stays dry for weeks can start leaking when the weather changes. Meteorological Service Singapore (MSS) describes the inter-monsoon months (April, May, October and November) as transitional periods with light and variable winds, when thunderstorms, at times severe, occur in the afternoon and early evening. The Northeast Monsoon runs from December to early March, and higher rainfall occurs from November to January during its wet phase (MSS climate page).

A short, severe storm can drive rain sideways under tiles and flashing, and can bring more water than a part-blocked gutter can carry. Long wet spells give water time to soak into hairline cracks on a flat roof.

If your leak appears only in storms, or only after several days of rain, tell the roofer, because that detail narrows down the cause. For checks to do around the house before the wet months, see our monsoon home care tips.

Gutters and mosquitoes

Gutters matter twice on a landed home: a blocked gutter overflows into the roof, and standing water in it can breed Aedes mosquitoes. Through its Mozzie Wipeout, the National Environment Agency (NEA) asks you to remove stagnant water weekly. Once a month, it says, add the prescribed amount of sand granular insecticide to roof gutters, even if they are dry, and clear fallen leaves from roof gutters and apron drains (NEA preventive measures).

Clearing the leaves also keeps rainwater moving to the downpipes instead of backing up under the roof edge. Our guide on how to prevent mosquito breeding at home covers other spots, and the landed home maintenance checklist sets out routine gutter and roof checks.

Who to call

The right trade depends on where the water gets in:

If you are unsure, start with a roofer for a pitched roof and a waterproofing specialist for a flat one. A handyman may help with smaller jobs such as clearing gutters, so ask what they cover before you book.

The cost depends on the job, so compare quotes that describe the same work. See plumber or waterproofing specialist for how the two trades differ.

The Building and Construction Authority (BCA) says insignificant building works do not require plan submission to BCA. For other works, consult a Qualified Person, and approvals from other authorities may still be needed (BCA guidance). If a contractor suggests rebuilding part of the roof, ask whether a Qualified Person is needed.

For more on damp patches and seepage, see our leaks and seepage questions.

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