What Are the First Signs of a Roof Leak?

Why the Ceiling Is Late

Water getting past a covering has to soak the underlay, run along timber, wet the insulation and then saturate a plasterboard ceiling before anything shows in the room.

On a modern roof with insulation in the loft, that can take a season. The insulation absorbs a surprising amount before anything gets past it.

Which means that by the time you see a mark on a ceiling, the timber above it has been wet through at least one winter - and that is the difference between a tile job and a tile-and-battens job.

In the Loft, in Order of Appearance

Go up in daylight, twice a year, and turn the light off before your eyes adjust. It takes five minutes.

Daylight through the covering. The earliest and most obvious. Often at a verge, around a chimney, or where underlay has torn.

Dark patches on the underside of the underlay. The very first sign of water arriving, long before it drips.

Staining on rafters and battens, particularly a vertical run down a rafter, which is water travelling.

Insulation that has flattened or discoloured in one area. Mineral wool that has been wet compresses and never recovers its loft, so a patch that looks thinner or darker than the rest is a marker even when it is dry today.

Rust on nail heads and nail plates, or beads of water on them.

A new draught where there was not one.

Joists only, torch in hand, and not at all if the loft is unboarded, cramped or you are not steady.

The Signs That Are Not in the Loft

A musty smell in an upstairs room, particularly one that is not used much. This is genuinely the thing people most often notice first, and it is almost always dismissed.

Peeling or bubbling paint at the top of a wall or on a ceiling, before any actual stain appears. Moisture behind the paint lifts it first.

Wallpaper lifting at a seam near the ceiling.

A hairline crack in a ceiling that was not there. Plasterboard that has been damp moves.

A heating bill that has gone up for no reason. Wet insulation stops insulating, and a soaked patch of loft quilt is a hole in the thermal envelope.

Condensation or mould appearing in a room that never had it, which can mean more moisture in the building than there was.

The Frodsham Early Warning

In a town with this many mature trees close to the houses, there is a warning that comes before any of the above.

Gutters and valleys filling. A gutter with plants growing in it, or a visible dam of leaf litter in a valley, is not a leak - it is the thing that causes one, and it is visible from the ground months before any water gets in.

A valley that is partly dammed will back up in the first heavy rain of the winter and push water sideways under the tiles either side. Nothing has failed; nothing needs repairing; it needs clearing.

Debris in the back gutter behind a chimney does the same and is harder to see, though sometimes visible from higher ground or a neighbouring window.

Moss falling into the gutters in quantity after a windy spell, which is where the dams come from.

Once a year after leaf fall is the interval, and it prevents more expensive leaks than anything else on this page.

What to Do When You Find One

None of these is an emergency. All of them are a booking.

Photograph what you found, note the date, and check again after the next spell of wet weather to see whether it is getting worse.

If it is daylight through the covering, or wet timber rather than a stain, that is worth acting on this month rather than next season - because the timber is the expensive part.

And if it is a full gutter or a dammed valley, that is the cheapest possible outcome and it is worth dealing with before the winter rather than after it.