How to spot the early warning signs of a failing roof

A roof rarely goes from “fine” to “leaking badly” in one step. There are almost always signs first — small, easy to ignore, easy to put off. The trick is knowing which signs matter.

Inside the house

Ceiling stains that appear after rain and disappear afterwards are the classic early signal. The water is finding its way in during rain and drying out between showers. By the time a stain is permanently dark, the leak has been running for a while.

Paint bubbling or peeling on upstairs walls — particularly on external walls, particularly near the ceiling line. Often mistaken for condensation. Usually isn’t.

A musty smell in the upstairs rooms or loft that you can’t pin on anything specific. Mould needs moisture. If you’ve got mould and you can’t see where the moisture is coming from, look up.

Light visible in the loft from outside — go up on a sunny day, close the loft hatch, and see if any daylight is getting through the roof. If it is, water can get in too.

Outside the house

You don’t need to get on the roof to see most of these. Binoculars or the zoom on your phone camera are enough.

Tiles or slates that have slipped out of line — the roof line should be straight and uniform. If you can see one tile that’s lower, higher, or at a different angle, something’s moved.

Cracked or missing mortar on the ridge — the ridge is the top course of tiles or the capping stones along the apex. Mortar there should be intact. If you can see gaps, that’s where water’s getting in.

Sagging in the roofline — a small dip or bow in what should be a straight line. This is more serious and means structural movement, not just a slipped tile. Worth a call sooner rather than later.

Green staining running down the wall below the gutter — usually means the gutter’s overflowing or the fascia’s failing. Not a roof problem yet, but if left it becomes one.

In the loft

If you can get into the loft safely, go up there after a rainy day and have a look with a torch.

Wet timber — rafters, purlins, or the back of the roof decking should be dry. Damp wood feels cold and often looks darker. Dry wood feels warmer and lighter.

Drips or puddles on the loft floor insulation — the insulation will be wet in a clearly localised spot, not generally damp throughout.

Compressed or matted insulation — sometimes a sign that someone’s been walking in the loft and has packed the insulation down. Compressed insulation doesn’t perform. Worth knowing if you don’t want to replace it.

The ones that don’t matter (yet)

A few things look alarming but are usually benign:

• Moss on the tiles — usually cosmetic on a pitched roof. Worth keeping an eye on if it’s very heavy, but not urgent.
• A single missing tile on a calm day — annoying, not catastrophic. The felt underneath should keep things dry for a while.
• Discolouration on chimney pots — they fade with age.

What to do when you’ve spotted something

Take a photo and note roughly where it is on the house (“front bedroom ceiling, north-east corner”, say). If it’s an internal sign, mention when it appeared and what the weather was doing at the time.

Then book a free survey. We’ll come out, look at the roof from outside and the loft from inside, tell you what’s actually going on, and write it up properly — even if the answer turns out to be “nothing that needs doing right now, here’s what to watch for.” Most early signs are cheap to fix. Most late signs aren’t.