Finding and Fixing a Leak

A roof leak is not always directly above the damp patch you can see indoors. Water can enter through one part of the roof, travel along underlay, rafters or other surfaces, and only become visible several feet away. That is why simply repairing the roof above a ceiling stain can leave the real fault untouched.

A proper leak investigation starts by working out how the water is getting into the building, then tracing that back to the defect causing it.

What different roof leaks can look like

Some leaks are obvious: water drips from the ceiling every time there is heavy rain. Others are much less consistent.

You might notice:

• a brown or yellow stain gradually appearing on a ceiling
• damp or staining around a chimney breast
• a leak that only happens during heavy or prolonged rain
• water ingress only when rain is being driven from a particular direction
• damp appearing after a storm but not during normal rainfall
• wet insulation or timbers in the loft without an obvious ceiling leak
• staining that disappears for months and then returns.

Those differences are useful clues. A leak that only appears in wind-driven rain, for example, can point us towards a different defect from one that develops steadily after several hours of rainfall.

It is also important to establish that the problem really is a roof leak. Condensation inside a roof space or chimney can produce damp patches that look surprisingly similar to rainwater penetration.

Finding where the water is actually entering

We inspect the roof as a complete weathering system rather than concentrating only on the point where the customer sees water.

Around a chimney, that means checking the chimney stack itself as well as the surrounding roof. Typical areas include the lead apron and cover flashings, individual soakers where applicable, the back gutter behind the chimney, pointing, brickwork, chimney pots, flaunching at the top of the stack and the tiles or slates immediately around it.

Cracked flaunching can allow water into the top of a chimney. Weathered pointing or porous, deteriorating masonry can let rain through the stack itself. Lead can split, lift, become poorly secured or have inadequate detailing at joints. A slipped or cracked tile nearby can produce symptoms that make the chimney look responsible when it is not.

Valleys, ridges, roof junctions, gutters, roof windows and other penetrations can cause similar problems elsewhere on a roof.

This is one reason we avoid diagnosing a leak from a photograph of the damp patch alone.

How we investigate persistent or difficult leaks

We start by asking what the customer has actually observed. When did the leak first appear? Does it happen every time it rains? Does it need strong wind? Is it worse after hours of continuous rain? Has any previous repair been carried out?

We then inspect the outside of the roof. BB Roofing uses a drone inspection where appropriate, giving us a good overall view and allowing us to examine areas that are difficult to see safely from ground level. Where necessary, we follow this with closer physical inspection of particular details.

We also look inside the loft or roof space where access is available. Water staining on timber, underlay or masonry can help us trace the route the water has taken. The first wet point is often more informative than the final drip.

The important part is putting all those observations together. Finding one cracked tile does not necessarily prove that it caused the leak. Likewise, replacing a piece of lead because it looks old is not much use if the real problem is defective masonry higher up the chimney.

Our survey report explains what we have found, the likely route of water ingress and the repair we recommend before work starts.

Repairing the cause rather than the symptom

The appropriate repair depends on what the investigation finds. It might be a relatively small job such as replacing damaged tiles or slates, repairing leadwork or repointing a localised area. A chimney leak can require work to the flashing, soakers, back gutter, brickwork or flaunching — and sometimes more than one of these.

Good detailing matters particularly around chimneys because several materials and roof surfaces meet in a small area. Water has to be directed safely around the stack and back onto the roof covering without finding a route underneath it.

Where previous patch repairs have failed, we look at why. Repeated applications of sealant or mortar may temporarily hide a defect without correcting the way water is getting through. Removing unsuitable repairs and reinstating the detail properly is often the more dependable solution.

What to do while you are waiting for a roofer

If water is already entering the house, move furniture, electrical equipment and valuables away from the affected area if it is safe to do so. Use containers or waterproof sheeting indoors to limit damage and take photographs of the leak and staining.

It is also useful to note what the weather was doing when the leak occurred. Rain direction, wind strength and how long it had been raining can all help with diagnosis.

Do not climb onto a wet or storm-damaged roof yourself. Avoid trying to solve the problem from inside the loft with expanding foam, silicone or other sealants. These can conceal the original water path and make subsequent investigation harder without providing a proper weatherproof repair.

If water is reaching electrical fittings, keep clear of the area and seek appropriate electrical advice.

Do not leave a small leak too long

A minor leak can remain hidden in insulation or roof timbers for some time before it becomes obvious downstairs. Continued wetting can damage plaster and decoration, saturate insulation and eventually contribute to timber decay.

Early investigation also tends to make diagnosis easier. A localised weathering defect may be straightforward to repair before water has affected a much larger area.

Emergency roof leaks

BB Roofing provides a 24-hour response for urgent leaks and can often attend the same day or the following day.

The first priority in an emergency is stopping further water getting into the property. If the permanent repair cannot sensibly be completed immediately — perhaps because specialist materials, access equipment or suitable weather conditions are required — we can often install a temporary weatherproof repair there and then.

We can then return to carry out the proper repair once the cause has been fully established and the work can be completed correctly.

Written by Benjamin Brown. Last reviewed on 16 October 2026.