Is a Leaking Roof Dangerous?

Electrical risk

Water and wiring is the most immediate danger. Water finds its way along joists and into ceiling roses, downlights, extractor fans and loft cables. A wet fitting can trip the circuit, or in the worst case give a shock or start a fire. If water is near any electrical item, switch off that circuit at the consumer unit, without standing in water, and do not use the light or switch. Have an electrician check the circuit before you use it again. Our page on a roof leak near lights or electrics goes through this in detail.

Ceiling collapse

A ceiling that holds water gets heavier by the minute. Plasterboard softens when wet, and a large pool can bring down the board and the insulation above it in one go. Signs are a bulge, a sag, cracks along the edges, and a wet stain that is growing. Keep out from underneath, and read our guide to what to do about a bulging ceiling. Older lath-and-plaster ceilings are heavier still, and a section coming down can cause injury.

Slips and falls

Drips onto hard floors or stairs create a slip hazard that people forget. Wipe up and use towels and buckets, especially if children or older people are in the house. Do not go up into the loft or onto the roof in the wet to look for the source. Wet joists and tiles are slippery, and a fall from a loft hatch or a roof causes serious injuries. Our guide to whether to go on the roof to check damage covers safer ways to look.

Damp, mould and health

Not all leak risks happen in the first hour. Repeated wetting leaves timber damp, and mould grows on plasterboard, insulation and wood. Damp conditions are unpleasant and can affect people with breathing difficulties, so talk to your GP if anyone in the house is affected. We are roofers, not medical advisers. What we can say is that the sooner the roof is watertight and the area dries, the smaller the risk. Our page on whether a roof leak can cause mould covers how it develops.

Structural damage that builds slowly

Water attacks the structure over months. Rafters, ceiling joists and wall plates that stay damp can rot, and wet insulation loses its value and holds moisture against the timber. Rusting nails and fixings weaken the roof covering. A leak that stops and starts may be doing more harm than it looks, because the timbers never dry out. Slow leaks are a good reason to book a survey sooner rather than later.

Danger to the roof itself

A leak is a sign that a roof is failing, and the failure can spread. Water behind a chimney flashing can loosen the brickwork and the pot. Water along the eaves rots the fascia and the rafter feet that carry the gutter. Water through a flat roof can rot the deck until a foot goes through it. These are not tonight's emergencies, but they show why a leak that has run for months is a bigger job than one caught in its first week.

Winter makes everything worse, because damp timber stays damp for longer in the cold and the roof space has less chance to dry between showers. Keep a record of how the leak behaves, whether it follows heavy rain, wind direction or a particular time of day, since that helps pin down the cause. Water in cracks freezes and expands, and the freeze-thaw cycle opens gaps that were hairline in autumn.

Which leaks need action tonight

Treat these as urgent: water near lights, sockets or the consumer unit; a bulging or cracked ceiling; water running in steadily; a hole or open section in the roof; or anyone at risk. A small drip in one place, away from electrics, can be caught in a bucket and reported in the morning, though it should not be left for weeks. Our guide on what counts as a roof emergency goes into this in detail.

What we do

We put emergency calls ahead of routine work, and the first visit is about stopping the water. After that we survey the roof, photograph the fault and explain what the repair involves, with a fixed price in writing. If the roof can be repaired rather than replaced, we say so. For a wider view of the work, see the emergency and general roof repairs hub.