Roofs rarely fail all at once. They give notice in small ways: a tile that sits a little lower than its neighbours, a stain on the loft felt, a gutter that overflows only in one corner. Most of these signs can be found without leaving solid ground, and the sooner they are read correctly the cheaper the answer tends to be. This checklist works from the outside in, then into the loft, then to the rooms below. For each sign it says what is usually behind it and how urgent it is, so you can tell a note-for-the-diary from a call-this-week.
Everything in this checklist is a fault that repair can usually fix. A roof that is past saving is a separate topic, set out under when to replace a roof.
What to look for from the garden
Stand back far enough to see the whole slope, ideally on a dry day with the sun low, because shadows show up things flat light hides. Binoculars help a great deal, and a phone camera zoomed in gives you a record to compare against next year. Do not put a ladder against the gutter to get a better view: the gutter is not designed to take your weight.
- Slipped, missing or cracked tiles. A gap where a tile should be lets wind-driven rain onto the underlay. Single cracked tiles often come from a branch, a ladder or a footstep, but a scatter of them across a slope suggests the tiles themselves are ageing.
- Slates that have dropped a few centimetres. Slates held by rusting nails slide down and leave a visible tail below the course. One slipped slate is a repair, while several in a row point to nail sickness, where the fixings have failed across the roof.
- A wavy ridge line or a dip in the slope. A roof line that is no longer straight can mean rotten timbers, a failing support or movement in the structure. This one deserves a prompt look.
- Crumbling or missing mortar at the ridge, hips and verges. The mortar bed under ridge tiles can crack and fall away, leaving the tiles loose. You may see grey debris on the ground below or in the gutter.
- Heavy moss or lichen. A green coat holds moisture against tile and can lift edges as it grows. A thin film is mostly cosmetic. A thick mat that fills the gaps between tiles is worth dealing with.
Details around the edges and openings
Most leaks start not in the middle of the tiles but where the roof meets something else: a chimney, a wall, a valley or a rooflight. Look at these junctions first. A flashing is the lead or metal trim that bridges the gap between the roof and a wall or chimney stack. Where it lifts, splits or has been smeared with sealant, water finds a way in. A valley is the internal angle where two slopes meet and drain into a channel; it gathers more water than any other part of the roof and tends to be the first to show wear, especially if leaves collect in it.
Check the chimney for a leaning pot, loose or cracked flaunching (the mortar cap that holds the pots in place) and for brickwork that has gone soft and sandy. Check any dormer, porch or extension abutment for lifted lead or a gap at the wall. If you can see daylight at an edge, or a sealant bead that has pulled away from the wall, the weatherproofing there has failed. If you already have a drip, tracing a roof leak to its source explains how water is followed back from the stain, and the entry point is often a flashing well away from where the drip appears.
Rooflights and roof windows deserve their own glance. Look for a cracked pane, a perished seal around the frame and any stain on the lining inside. The flashing kit that surrounds the frame is where most leaks begin, and it is easy to miss from the ground. Pipes and vents that pass through the tiles have a collar or lead tray around them, and a split collar on an old soil vent is a surprisingly common cause of a small, stubborn leak.
The roofline: gutters, fascias and soffits
The edge of the roof tells its own story. Gutters that overflow in a downpour, drip from a joint or hang at a slope are not just a nuisance. Water running down a wall can stain the brickwork, soak the fascia (the board that runs along the eaves, holding the gutter) and rot the soffit (the board beneath the overhang). Peeling paint, soft timber or a fascia that gives under a screwdriver tip point to water getting in behind the roofline. Green staining under a joint shows where a seal has gone. Plastic fascias that have sprung from their fixings, or gaps at the corners where a bird could enter, are worth fixing before nesting season.
A short grass seed or small plant growing in a gutter is a sign of years of trapped debris. Blocked gutters push water back under the lowest course of tiles, which rots the batten ends and the felt beneath. A clear gutter is a cheap form of roof protection.
Signs inside the loft
The loft shows the underside of the roof, and that is where a lot of evidence collects. Go up with a torch on a bright morning and switch the light off for a moment: any pinpricks of daylight coming through are gaps in the covering. Then look for the following.
- Damp or dark patches on the underlay or timber. A stain with a tide mark means water has been arriving repeatedly. Fresh, wet patches after rain point to an active leak.
- Torn, sagging or brittle felt. Old bitumen felt dries and cracks. Where it is torn, wind-driven rain has nothing to stop it.
- Soft or darkened rafters and battens. Press a screwdriver into suspect timber. If it sinks in, the wood is decayed. Pale fungal threads or a musty smell suggest long-term damp.
- Condensation and black mould on the underside of the roof. This is a ventilation problem as much as a roof problem, and it can mimic a leak. Our answer on condensation in the loft explains how to tell the two apart.
- Wet or compressed insulation. Insulation that stays damp loses its value and keeps timber wet.
Signs in the rooms below
By the time a stain is on the ceiling, water has usually been travelling for a while. Look for brown or yellow rings on ceilings, especially on the top floor or near a chimney breast. Look for bubbling or peeling paint, wallpaper lifting along an external wall and a damp smell in a room that has no other reason to be damp. A stain that grows after rain and shrinks in dry weather is an active leak. A stain that never changes may be old damage that has dried, but it still deserves a look from above because the cause may have returned.
Sudden or severe symptoms are a different matter. A ceiling that is bulging with water, a drip you can hear or one that runs along a light fitting calls for immediate action: keep clear of the area and contact an electrician if water is near wiring. If water is coming through now, our page on water coming through the ceiling sets out the steps in order.
When in the year to look
Two checks a year catch most developing faults. Early autumn, before the leaves fall and the wet weather settles in, is the time to look for anything that will not survive a winter: loose ridge tiles, lifted flashings, blocked valleys and gutters. Late spring is the time to look for what winter did, such as frost-split tiles, slipped slates and damp that appeared in the loft. After any named storm or a night of strong gusts, a quick walk round the house with binoculars costs nothing and can save a bad surprise later.
If your house has trees close by, add a look in late autumn once the leaves are down, because a roof under an oak or sycamore collects debris in valleys and gutters faster than one in the open. Trees also drop twigs and the odd heavy branch, so a post-storm look matters more there.
Which signs can wait and which cannot
| Sign | Usual meaning | How soon to act |
|---|---|---|
| One slipped or cracked tile | Local damage, often from impact | Within a few weeks, before the next wet spell |
| Moss across a north slope | Shade and moisture, mostly cosmetic at first | Plan it into the next maintenance visit |
| Lifted or split flashing | Open path for water at a junction | Soon, as it will leak in the next heavy rain |
| Daylight showing through the loft | Gap in the covering or ridge | Promptly |
| Active drip or growing ceiling stain | Water entering now | Immediately: make it safe, then call |
| Dip or wave in the roof plane | Possible timber or structural fault | Prompt survey, before any other work |
What your findings mean for repair or replacement
A single sign on its own rarely tells you the whole story, and a handful of signs together do. One lifted flashing with a healthy roof around it is a repair. Slipped slates, moss across both slopes, a sagging felt and damp battens together describe a roof that is wearing out. Our companion guide on deciding between repair and replacement shows how we weigh these combinations, and the annual routine in our roof maintenance checklist keeps small signs from turning into big ones.
Take dated photographs as you go. If you later claim on insurance or sell the house, a record of what the roof looked like and when is a real advantage. Note which room and which wall showed damp, and what the weather was doing at the time, because the pattern helps trace the entry point.
When to ask for a survey
If you have found one or two small signs, a survey will tell you whether anything is actually wrong. If you cannot reach the area, or you spot structural signs such as a dip or a bulging ceiling, book one sooner. We go on the roof and into the loft, photograph what is there and tell you what needs doing, in what order, and what can wait. Where a repair is enough you will hear that, and where it is not you will get the reasons and a written quote. The work is covered by a written 10-year workmanship guarantee. For a second opinion on what you have spotted, send a picture over WhatsApp or ring 01256 213956. You can also return to our home page to see everything we do.
