Re-roofing is one of the largest repairs a house will need, and the temptation is to start with the number. Two or three roofers each glance at the slopes, name a figure and leave. The figures come back thousands apart, and nobody can say why. The usual reason is that none of them was pricing the same roof. One assumed the battens were sound; another assumed they were not. One allowed for new lead at the chimney and valleys; another left it out. A survey comes first because it settles those questions before money is attached to them. It records what is on the roof, what lies beneath, what must be renewed and what can stay, and it gives every quote the same starting point. A pre-replacement survey should cover set ground, it prevents costly surprises once the old covering is off, it ties into Building Regulations and consent, and it gives you a fair way to compare quotes.
What a quote without a survey leaves out
From the ground you can see the covering. You cannot see the battens, the underlay, the rafters, the wall plates or the condition of the lead at the abutments. Those hidden parts decide whether a new covering will last, and they decide the final bill more often than the slates or tiles do.
A quote built from a street view has to make assumptions, and each assumption can be wrong in either direction. If the roofer assumes the timbers are sound and finds them rotten halfway through the job, the price rises mid-contract, usually with the roof already stripped and open to the weather. If the roofer assumes the worst, the quote is padded to cover it, and you pay for work that may never be needed. Neither is a fair way to buy a roof.
A survey removes the guesswork by looking first. It also changes the conversation. Instead of asking for a price, you ask for a specification: which covering, which underlay, whether the battens are renewed, what happens to the lead, how the ridge is fixed, what the scaffold involves and where the waste goes. Quotes returned against the same specification can be compared line by line, and the differences tell you something useful. A low figure that leaves out new battens is not low. It is a different job.
The same principle applies if you only need a repair. A survey tells you whether a patch will hold or whether you are paying for a fix to a roof that is failing everywhere. The signs that point towards replacement are listed on our page about a roof reaching the end of its service, and the roof inspections hub explains how we carry out the survey itself.
What the survey should record
A useful pre-replacement survey is specific. It looks at the whole roof and writes down what it finds, with photographs.
The covering
It identifies the material (natural slate, clay or concrete tile, stone tile, artificial slate) and its condition: how many are cracked, slipped, delaminating or worn, and whether the fixings are failing. A slate roof with rusting nails will keep dropping slates however good the slate is, a pattern heritage guidance calls nail sickness.
Battens, underlay and timbers
It checks the battens that carry the covering, the underlay beneath them and the rafters, from the loft where possible. What that part can reveal is covered in the page on the loft roof inspection.
Lead and the detailed parts
Valleys, flashings, soakers and parapet or box gutters are checked individually. A box gutter works as a lined channel that drains the water from adjoining slopes, often concealed behind a stone parapet. A valley is the same idea at the meeting of two pitches. If the lead in either has gone, the new covering above it is compromised, so we renew it while the roof is stripped.
Ridge, hips, verges and chimneys
The survey notes how ridge and hip tiles are fixed. BS 5534 treats bedding mortar as insufficient for ridge and hip pieces, so a clip or screw fixing is expected. It also looks at the chimney stacks, their pointing and flaunching, and their flashings.
Access and the edges
Gutters, fascias, soffits and the scaffold position are recorded, because they affect both cost and sequence.
Timbers and structure: the findings that change the price
The structure under a roof is where a survey earns its fee. Rotten battens are replaced as a matter of course on a re-roof, but rafters and wall plates are different. If a rafter foot has decayed, sections have to be repaired or sistered with new timber before the covering goes back, and that is carpentry as well as roofing.
The survey also asks whether the roof structure can carry what is planned. Extra weight loads the frame. Weight is the trigger here: a heavier covering, by 15 per cent or more, means approval and a check on whether the frame copes. Switching from artificial slate to natural stone tile, or from concrete tile to a heavier clay product, can trip that threshold, which is far better learned at survey than after the materials are ordered.
Sagging ridges, bowed slopes and spreading walls are signs of structural movement. They may be old and stable, or they may be active. A survey cannot always tell which, and where it cannot, it should say so and recommend a structural engineer's opinion before the covering is renewed over a problem that will return.
Wildlife is another early question. Signs of bat use or an active nest in the loft or at the eaves mean the programme must be shaped around the animals, which the law protects. And if there is any possibility that old sheets, boards or insulation contain asbestos, they should be identified at survey and handled properly, never disturbed in the course of work.
Permission, regulations and the survey on a Bath roof
Whether a re-roof needs approval depends on its size, and a survey is how the measurement is made. The Planning Portal puts the usual exemption for re-covering at work for jobs kept to a modest patch: under 25 per cent of the envelope, under 50 per cent of the roof. A full re-roof is far past both limits. Approval then applies, and the roof element may need upgrading to today's thermal standard, so insulation joins the specification and the price. The Planning Portal re-roofing guidance sets out the rules, and the survey should list what the upgrade involves so it appears in the quote and not as a surprise.
In Bath the survey does a second job. UNESCO inscribed the city as a World Heritage Site in 1987, and the conservation area extends across about one half of its area. Around 5,000 buildings here are listed. Changing the covering on a listed house generally requires consent from B&NES, and doing the work without it is an offence. A few streets also carry Article 4 directions, which the council's policy map shows. A survey that identifies the listing, the conservation status and the existing materials lets the planning question be asked early, with photographs, and not after the scaffold is up.
Matching matters here. Casework from the Bath Preservation Trust shows the sort of detail that is looked at: natural Welsh slate preferred to artificial slate, lime mortar in place of cement around old stonework. Our approach is to put right the roof that was built, so the survey records the real roof before anything is specified.
We handle the Building Regulations notification where the work is notifiable, and the survey is where we work out whether it is.
How the survey keeps cost under control
On typical UK ranges reported by MyBuilder (2026), a roof replacement costs between £5,000 and £12,000, with scaffolding adding about £1,125 and waste disposal between £100 and £1,000. A standard roof inspection runs at about £150 to £250. Those are national figures, not ours; our own price is fixed in writing once the survey is done. Set side by side they show the proportion. A survey costs a small fraction of the job it protects, and one unexpected structural repair can cost more than the survey several times over.
The survey keeps cost down in three ways. First, it prevents variations: when the specification is complete, the price does not move halfway through. Second, you can decide what to renew and what to keep while looking at the photographs. Re-using sound slates, keeping good lead, or repairing a section instead of replacing the whole roof are all choices that only make sense once the condition is known. Third, it shows where thermal upgrade, scaffold and access will fall, so you can plan them.
If a repair is enough, the survey says so. We repair where repair works, and a survey is the document that proves whether it does. For the costs of the survey itself, our page on roof survey cost goes through the ranges.
Some roofs call for extra tools. Where moisture is suspected in a flat roof, or where a large commercial roof needs to be mapped for wet insulation, thermal imaging can help narrow the search, though it supplements a proper inspection and does not replace it.
Using the survey to compare quotes
Once you have a survey, use it as the yardstick. Send the same specification to each roofer and ask them to price against it. Where a quote departs from it, ask why. A good roofer will either follow the specification or explain, with reasons, what they would change.
Read each quote for the same list of items. Does it say which covering and from what source? Does it renew the battens and the underlay, or reuse them? Does it renew the lead, and where? How is the ridge fixed? Does it allow for scaffold, for stripping, for skips and waste? What happens to the chimney flashings? Is the Building Regulations notification included, and who makes it? And what is guaranteed, for how long, and in what form?
Our own written guarantee is for ten years of workmanship, and it is set out on paper. It is not backed by insurance, and we say what it covers. Ask any roofer the same questions, and ask to see the wording before you decide.
A fixed price in writing should follow the survey, with the specification set out item by item. If a roofer cannot or will not price against a survey, that is informative. The cheapest quote is not necessarily the one that costs least once the roof is open.
Take your time. A roof that has lasted for many years will usually survive another few weeks while you check what is under it, unless it is leaking, in which case we make it safe first and survey after. Then the roof can be replaced once, and replaced properly.