What a roof survey checks, top to bottom

A survey does not begin on the roof. It begins at the kerb, with a look at the whole shape. From there you can see things that vanish once you are standing on the slope: a ridge line that dips where the timbers underneath have settled, a slope that bellies out, a chimney that leans, a run of tiles that sits proud of its neighbours.

The ground walk covers the walls too. Damp patches on brickwork under a gutter, green staining below a parapet, and render that has blown near a flashing all point back to the roof. Photographs are taken from each side of the building so the written findings can refer to a slope by its position, such as the front slope or the side facing the sea.

Why the outline comes first

Settlement and sag are hard to judge from close up and easy from a distance. A mismatch between the original roof and a later extension, a lean-to drifting off the house wall, and a porch roof sitting at a different angle from the main roof are all picked out here and marked for a closer look later.

It is also when the access plan is made. Will a ladder reach? Does the covering look safe to walk on, or is it slate or old clay that would crack under a boot? Can a tower go up on the drive, or does the front sit directly over the pavement? Those answers decide whether the rest of the survey is done from the roof, from a drone or through the loft, and they are settled before anyone leaves the ground.

Next comes the covering: the tiles, slates or membrane that shed the water. On a pitched roof the surveyor looks for slipped, cracked, chipped or missing pieces, for tiles that have lost their nibs (the small lugs that hook them over the batten), and for moss or lichen sitting thick enough to hold moisture against the surface.

On slate the question is nail fatigue. Slates hang from nails, and the nails give out before the slate does, which means a handful of slipped slates may be the first sign that a whole slope needs relaying. For well-maintained natural slate, CORC gives 100 years or more. Marley expects concrete tiles to last around 60 years and is careful to call that no guarantee. Age is a clue, not a verdict.

Pitch also matters. Each tile and slate has a minimum pitch in its manufacturer's data sheet, and Cupa Pizarras reads BS 5534:2014+A2:2018 as putting the floor for natural slate at 20 degrees, for a 500 mm slate. A covering laid below its minimum can leak whatever the condition of the individual pieces.

Flat roofs

On a flat roof the survey is about water that stands. BS 6229:2025 keeps a minimum finished fall of 1:80, and roofers usually aim for about 1:40 so that the roof ends up draining properly. Ponding, blisters, split seams, lifted edges and cracked trims all get photographed. Lifespans differ widely: Less gives torch-on felt 10 to 20 years, GRP 25 to 40 and EPDM 30 to 50. Our guide to a flat roof survey goes into those checks in detail.

Along the apex runs the ridge. Down the angles of a hipped end run the hips. The gable edge, where the covering stops short of the end wall, is the verge. These are the parts that take the worst of any gale, so the survey spends time on each.

The first question is how the capping is held. BS 5534 changed in 2014 so that a bed of mortar can no longer be the only thing holding ridge and hip tiles; each one is fixed with a screw or clip as well. BS 8612:2018 covers dry-fix systems, which hold the capping to a frame with clips and screws and use no bedding mortar at all.

On an older roof the signs are mortar that has cracked, crumbled or dropped away, and capping tiles that rock when pressed. Where the ends of a ridge show no visible fixing, that is noted and photographed.

Verges and eaves

At the verge, the survey checks whether the tiles are mortared, clipped or dry-fixed, whether the mortar has failed, and whether the bargeboard behind it has started to rot. At the eaves it looks at the first course of tiles, the lap of the underlay and whether the overhang is carrying water into the gutter and not letting it run behind the fascia.

A ridge in poor shape is among the commonest reasons a patch repair turns into something larger, so this part of a report often carries the most photographs. Our page on ridge tile repairs shows how the work is done once the survey has found the fault.

Any join between the roof and something upright, such as a party wall, a stack or a dormer cheek, relies on a flashing: metal dressed over the seam so water cannot track behind the covering. These junctions are among the most common places for a leak to start, so a survey takes its time over them.

Flashings are normally lead. The surveyor looks for lead that has cracked, lifted or slipped, for sealant smeared where metal should be, and for gaps at the top edge where the lead tucks into the brickwork. Soakers are the small bent pieces of lead interleaved with the tiles at an abutment, and they can only be judged properly where the covering is lifted. Lead comes in numbered codes by thickness; Royston Lead's brochure says code 3 suits soakers alone, with code 4 the thinnest it lists for flashings. MyJobQuote puts the life of lead flashing at over 80 years, so a failure is often down to how it was fixed, not its age.

The stack itself

On a chimney the survey checks the pointing between the bricks, the flaunching (the sloped mortar collar around the pots), the pots and cowls, and whether the stack leans. Photographs are taken from the roof or by drone, as a stack is hard to judge from below.

A chimney that is no longer used can still let water down into the house, which is why a survey asks whether the flue is capped and ventilated. Our page on chimney repairs covers the work that follows when a fault is found, and the lead roofing and leadwork page covers flashing repairs.

The roofline is everything at the edge: gutters, downpipes, fascias (the boards the gutters are fixed to) and soffits (the boards under the overhang). A survey treats it as part of the roof because water that leaves the roof has to get away cleanly.

The checks are simple but they matter. Are the gutters level enough to drain? Fall guidance from manufacturers runs from about 1:600 down to 1:350, depending on the system, and one maker, Brett Martin, wants supports at 900 mm centres at most. Are there joints that weep, sections that sag between brackets, or downpipes that discharge onto a wall instead of a drain? Is there moss, silt or a bird's nest in the run?

Fascia and soffit boards are tapped and prodded for rot, particularly under a leaking joint. Painted timber that bubbles, boards that have gone soft and gaps where a soffit meets the wall are all recorded with a photograph.

A note on soffits and asbestos

Where a building dates from before 2000 or was refurbished then, HSE's advice is to assume asbestos could be in it. External soffits can be made of asbestos insulating board, and HSE notes that this board and its modern equivalents are hard to tell apart by eye. If a soffit looks like that material, the survey records it as suspected and stops there. Nothing is cut or drilled until the material has been identified properly, and the report says so.

Gutters and the roofline have their own page on guttering, soffits and fascias.

The last stage is the loft, because it shows the roof from the side that water reaches last. Armed with a torch, the surveyor looks at the underside of the covering for daylight, at the rafters for staining or darkening, at the insulation for wet patches, and at nail tips for rust. Tracing a stain on a ceiling back to its source usually ends here. Our guide on what you can check from the loft yourself lists what to look for.

Ventilation and insulation

The survey also looks at how the roof breathes. Marley gives a 25 mm opening along the eaves up to 15 degrees of pitch, and 10 mm above that, where the underlay is the high-resistance kind. Condensation on the underside of the covering and mould on timber point to poor airflow. Foam sprayed onto the underside hides the timbers from view, and Energy Saving Trust advice on spraying foam onto a roof that already leaks is that it does not recommend it. Roofs also shelter wildlife: bats are protected, so a survey that finds signs of bats or an active nest stops and says so.

Then the findings are written up. A good report names each fault, shows the photograph, says how urgent it is and ends with the verdict. It follows the order the survey was done in, so you can read it against the roof. Our answer on what a roof inspection report should include sets out the details, and our roof inspections and surveys page explains how to book one. If work is needed, the quote that follows is in writing and gives one total.