Roof Leak Finder: Where Is Your Roof Leaking From?

How to find where a roof leak is coming from

The damp patch on your ceiling is rarely directly below the fault. Water gets in higher up, runs along a rafter, a batten or the underlay, and drips down somewhere else. Finding the source means working back from the stain.

1. Start in the loft. During or just after rain, take a torch into the loft and look above the damp patch. Check the rafters and the underside of the underlay for drips, dark staining or water trails.
2. Follow the trail upwards. Water runs downhill, so the entry point is usually higher up the slope than where it drips. Look for daylight, wet timber, or a torn patch of underlay.
3. Check the usual suspects. Chimneys, roof windows, valleys and the joint between a flat roof and the house wall cause most of the leaks we find.
4. Look outside from the ground. With binoculars, look for slipped or missing tiles, lead flashing that has lifted, cracked mortar on the ridge, and gutters that overflow or sag. Don't climb onto the roof.
5. Note when it happens. A leak that only appears in wind-driven rain points to a different fault from one that appears in any rain. The leak finder above uses this to narrow it down.

Water coming through the ceiling: what to do

• Put a bucket under the drip and move furniture, rugs and electronics out of the way.
• If water is near a light fitting or socket, switch that circuit off at the consumer unit and don't touch wet fittings.
• If the ceiling is bulging, put a bucket underneath and make a small hole in the centre of the bulge so it drains in a controlled way, rather than collapsing.
• Photograph the damage inside and anything you can see outside. Your insurer will want the photos.
• Call a roofer. Our 24-hour emergency roofing service can make the roof watertight while a permanent repair is planned.

Roof leaking after heavy rain

If your roof only leaks after heavy or prolonged rain, it is usually coping until it is overwhelmed. Common causes are blocked gutters overflowing back under the tiles, a valley or hidden valley gutter full of leaves and silt, and water ponding on a flat roof until it finds a weak seam. Clearing gutters and valleys fixes some of these. Others need a roof repair to the valley lining or the flat roof covering. Our guttering service covers clearances, repairs and replacements.

Roof leaking around the chimney

Chimneys cause a large share of the leaks we see on period homes in Croydon, Bromley and Surrey. Water gets in through failed lead flashing at the base of the stack, cracked flaunching on top, missing pots or caps, and porous brickwork. Damp on a chimney breast in dry weather is more often condensation inside a capped flue. Our chimney repair service covers flashing, repointing and rebuilds.

Flat roof leaking

Flat roofs on extensions, garages and dormers leak most often where the roof meets the house wall, at splits and open seams in old felt, and where water ponds in dips. A single split can be repaired, but a flat roof that leaks in several places is often due for replacement. Our guide to GRP, felt and liquid flat roofs compares the options, and our guide to repairing or replacing a roof helps you decide.

Roof leaking when it's not raining

A roof leak needs water from outside. If damp appears on cold, dry mornings, the cause is almost always condensation: warm, moist air from the house meeting the cold underside of the roof. Poor loft ventilation and older flat roofs with the insulation in the wrong place are the usual culprits. A leaking pipe or water tank in the loft is the other possibility. Our guide to why roofs leak explains how to tell the difference, and our guide to whether insurance covers a leaking roof explains what to do about a claim.