If you have three quotes for the same roof and they differ by a factor of two, the most likely explanation is not that one contractor is greedy and another is generous. It is that you have three quotes for three different jobs.
This guide is about getting them onto the same footing so you can actually compare them. It is not about spotting villains. Most of the confusion in roofing pricing is genuine ambiguity rather than anything worse, and it clears up as soon as somebody writes down what is actually being priced.
Why the same roof produces wildly different prices
Because a roof is not a product with a price, it is a set of decisions, and each quote has silently made its own.
Consider a tired flat roof on a rear extension. One contractor looks at it, finds the deck sound, and prices an overlay: nothing is stripped, the existing covering stays, and the skip and the disposal charge come out of the job. Another looks at the same roof, decides it is at the end of its life, and prices a strip and replace: the covering comes off, the deck is exposed, waste goes to landfill and there may be an insulation upgrade under building regulations at the far side of it.
Both may be entirely honest. They are answering different questions. The overlay quote answers “what is the cheapest way to make this roof watertight for the next decade”, the replacement quote answers “what does it cost to start again”. Neither is comparable to the other until you know which one you are looking at.
Layer on top of that the variables that move a price without changing the roof at all: whether scaffolding is included, whether the waste is included, whether the details are included, what covering has been assumed, and whether VAT is in the number or under it. Any one of those can be a quarter of the total.
What a quote should itemise
Enough for you to reconstruct the job from the paper without the contractor standing next to you. In practice that means these things.
The scope of the strip-out. What comes off, and what stays. On a flat roof, whether the existing covering is being removed or overlaid. On a pitched roof, whether it is a patch, a slope or a full strip.
The system, by name. Not “a liquid coating” or “a rubber roof” but the specific system, its manufacturer and, where one exists, its certification. This is the single most important line in the quote and the one most often missing. A named system can be researched. An unnamed one cannot.
The area, in square metres. With the measurement stated, not implied. Worth knowing on a pitched roof: the actual roof area is larger than the footprint of the building, typically by a factor of 1.2 to 1.5 depending on the pitch, so a quote based on a floor plan is under-measured.
Access. Scaffolding, tower or ladder, who supplies it, who pays for it, and how long it is on hire. Scaffolding is normally priced separately and it is a genuine cost line: roughly £700 to £1,500 on a typical two-storey house as an indicative market range, up to around £2,500 where access is difficult. On a fascia and soffit job it can be as much as a third of the total.
Waste. Who removes it and whether the cost is in the number. On an older roof, ask specifically whether anything is suspected to contain asbestos, because licensed removal of asbestos cement sheeting runs at roughly £55 to £95 per square metre as a market rate and is not something that gets absorbed quietly into a total.
The details. Flashings, upstands, outlets, verges, ridge, abutments and thresholds. Roofs leak at details, and details are where a low quote usually made its savings. If the detail work is not listed, ask what is included and what is not.
VAT. In or out, stated plainly.
The guarantee. Length, what it covers, who issues it, and whether you get it in writing at handover.
Payment stages. What is due when, and what triggers each stage.
Why a price per square metre tells you almost nothing on its own
Because the rate is meaningless without the specification it belongs to, and the ranges overlap.
As indicative UK market rates for 2026, and explicitly not as our quote: felt runs at roughly £40 to £80 per square metre, EPDM roughly £80 to £120, GRP roughly £100 to £150, and London labour typically adds 25 to 30 percent to national figures. Liquid systems are the widest spread of all, from about £40 to £180 per square metre.
That liquid range is worth understanding rather than hiding, because it is the source of most of the confusion in flat roofing. The spread exists because published sources mix two entirely different things under one heading: cheap acrylic coatings brushed onto a roof, and certified reinforced systems with a European Technical Assessment behind them and a trained applicator applying them. Certified systems sit at the upper end of that range. A quote near the bottom of it is not a cheaper version of the same thing.
So when you compare rates, compare like with like:
- A £45 per square metre coating and a £140 per square metre certified system are not competing offers. They are different products with different service lives.
- A rate quoted without a named system cannot be placed on that scale at all.
- A rate that looks reasonable can still hide an under-measured area.
Our flat roof cost guide sets out the ranges in more detail along with what moves the number within them.
Three specific warning signs on a liquid or coating quote
These come from trade guidance rather than from us, and they are worth checking on any quote for a flat roof coating.
No applicator certification from the manufacturer. Certified systems are certified as a combination of material and installer. If the contractor cannot say which manufacturer has approved them and produce evidence of it, the certification on the tin does not transfer to the work. K & M Roofing Solutions is a certified applicator of HYDRONYLON, a liquid-applied waterproofing system certified to ETA-23/0735, which is exactly the kind of claim you should be asking any contractor to evidence rather than taking on trust.
Vague wording with no named product. A “membrane refresh”, a “roof rejuvenation”, a “waterproof treatment”. If the paperwork does not name what is going on the roof, nothing about it can be verified, including the guarantee.
A price under roughly £18 per square metre on a roof more than ten years old. That figure is below what a certified reinforced system costs to supply and apply, so a price under it is either a thin coating or an underestimate that will be corrected once work has started.
Our article on what ETA-23/0735 certification means explains what an assessment of that kind actually covers and how to check that a claimed one is genuine.
Guarantees: two different documents
A workmanship guarantee and a product guarantee come from different parties and protect against different things, and a quote should tell you which of them you are getting.
Workmanship is the contractor guaranteeing the way the work was done. It covers installation faults: a badly formed upstand, an outlet that was not detailed properly, a lap that has failed. It is worth exactly as much as the business standing behind it will be worth when you need to call on it, which is a reason to look at how long the company has been trading and whether it is a registered company you can look up.
Product is the manufacturer guaranteeing the material. It normally survives the contractor going out of business, but it covers the material only. A manufacturer will not pay to correct somebody else’s installation, and many product guarantees are conditional on the material having been applied by an approved installer, which brings you back to certification.
The strongest position is both, from two separate parties. On our work that means a 10-year workmanship guarantee from K & M Roofing Solutions on everything, and on flat roofs finished with HYDRONYLON a separate 10-year product guarantee issued by HYDRONYLON LTD.
Two things to be wary of. First, any durability claim well beyond the guarantee period: if somebody tells you a system lasts 25 years but guarantees it for 10, ask which number is in the contract. Second, a guarantee that is described but never issued. Ask when you get the document and what it will say.
Questions worth asking every contractor
Ask all of them the same questions and compare the answers rather than the numbers.
- What exactly is coming off, and what is staying?
- Which system are you installing, who makes it, and are you certified by them to apply it?
- How did you measure the area, and what is it?
- Is scaffolding included, and how long is it on hire?
- Who removes the waste, and is it in the price?
- Which details are included: flashings, upstands, outlets, verges?
- Is VAT in this figure?
- What guarantee do I get, from whom, for how long, and when do I receive the document?
- What is your payment schedule?
- What have you assumed that would change the price if it turns out to be wrong?
That last question is the most revealing one on the list. Every quote for roofing contains assumptions about what is under the covering, and a contractor who can tell you what they have assumed and what would change is thinking about your roof rather than about the sale.
What we do, and why
Every quote we issue follows a free survey, because pricing a roof from a description or a photograph is guesswork dressed up as a number.
The quote is then itemised by element, so you can see what the strip-out, the system, the access, the details and the waste each cost, and drop or stage items if the budget needs it. Where we quote market figures for context they are labelled as indicative 2026 market rates rather than as our price. And where the survey finds that the roof does not need what you thought it needed, we say so: a repair we can do is worth more to us than a replacement you did not need and will tell people about.
If you want to see how the decision between repair, overlay and replacement is actually made before you read your quotes again, our guide to flat roof repair or replacement walks through what a surveyor is looking at. For what the systems themselves involve, see flat roof repair and waterproofing and liquid applied roof waterproofing.