Is My Builder's Quote Too Expensive? How to Tell
How to tell if a builder's quote is fair - cost per m² benchmarks by project type, regional multipliers, and the scope traps that make cheap quotes expensive.
You open the PDF. You scroll to the bottom. £78,000. Your stomach drops.
In short: Divide the total by the floor area to get a cost per square metre, then compare it against regional benchmarks. For a single-storey extension in England, £1,800-£2,400/m² is typical in 2026. If your quote is 20-30% above that without a clear reason, it is probably too expensive.
Is that right? Is it too much? You have no frame of reference. You've never built an extension before. The builder seemed decent. But seventy-eight grand?
That feeling - the mix of sticker shock and uncertainty - is exactly why you're reading this. If you're already suspicious, have a look at our signs your builder is overcharging piece for specific warning signals. Otherwise, here's how to work out whether your quote is fair, overpriced, or actually decent value.
First: ignore the total
Seriously. The total is the least useful number on the page. A £40,000 quote could be brilliant or terrible depending on what's behind it. Before you compare totals, you need to understand what you're comparing.
We'll start with the single most useful metric in residential construction.
The only number that matters: cost per m²
Total price is almost meaningless on its own. A £40,000 quote for a 12m² extension is very different from £40,000 for a 30m² one.
Cost per square metre is how the construction industry benchmarks projects. It strips out size and lets you compare apples to apples.
To calculate it: divide the total quoted price by the floor area of the new build. If your builder quoted £65,000 for a 20m² extension, that's £3,250/m².
Is that good? Depends on the project type and spec level. Here's what you should expect in 2026:
Cost per m² benchmarks by project type
| Project type | Basic spec | Standard spec | Premium spec |
|---|---|---|---|
| Single-storey rear extension | £2,200–£2,800 | £2,800–£3,500 | £3,500–£4,500 |
| Double-storey extension | £1,800–£2,400 | £2,400–£3,200 | £3,200–£4,200 |
| Loft conversion (dormer) | £1,500–£2,000 | £2,000–£2,800 | £2,800–£3,800 |
| Kitchen refurbishment | £800–£1,200 | £1,200–£2,000 | £2,000–£3,500 |
| Bathroom refurbishment | £1,200–£1,800 | £1,800–£2,500 | £2,500–£3,500 |
| Garage conversion | £1,000–£1,400 | £1,400–£1,800 | £1,800–£2,500 |
These figures are national averages for England and Wales, including labour and materials, excluding VAT. Your project might sit between categories - that's normal.
Basic spec means functional finishes. Standard kitchen, vinyl flooring, painted walls. Nothing wrong with it, but nobody's photographing it for Instagram.
Standard spec is what most homeowners choose. Decent kitchen, engineered wood or tile flooring, good quality windows. The sweet spot.
Premium spec is where you're specifying particular brands, stone worktops, underfloor heating, large-format glazing. Beautiful, but the costs reflect it.
Location changes everything
A builder in Sunderland and a builder in Surrey are not operating in the same economy. Labour rates, material delivery costs, even skip hire - it all varies by region.
Apply these multipliers to the national benchmarks above:
Regional cost multipliers (2026)
| Region | Multiplier |
|---|---|
| Inner London | ×1.30–1.40 |
| Outer London | ×1.15–1.25 |
| South East | ×1.05–1.15 |
| South West | ×0.95–1.05 |
| East of England | ×1.00–1.10 |
| West Midlands | ×0.90–1.00 |
| East Midlands | ×0.88–0.98 |
| North West | ×0.85–0.95 |
| Yorkshire & Humber | ×0.85–0.93 |
| North East | ×0.80–0.90 |
| Wales | ×0.80–0.90 |
| Scotland | ×0.85–0.95 |
So that £3,250/m² quote for a standard rear extension? In Manchester, it's a touch high. In Guildford, it's bang on. In Islington, it's a bargain.
Context matters. Don't just Google "average extension cost UK" and panic.
VAT: the 20% surprise
Before you compare your quote to any benchmark, check whether VAT is included.
If your builder is VAT-registered (compulsory once turnover exceeds £90,000), they must charge 20%. That turns a £60,000 quote into £72,000. Or put another way - a £72,000 VAT-inclusive quote is really £60,000 of work.
Some smaller builders aren't VAT-registered. That's not a red flag - it just means their turnover is below the threshold. But it does mean you can't compare their quote directly to a VAT-registered builder without adjusting.
Always check whether the total includes VAT. If the quote doesn't say, ask. This single detail explains a huge number of "why is one quote 20% more?" conversations.
The spec problem
Two builders can quote for the "same" kitchen extension and price it completely differently because they're assuming different specifications.
Builder A specifies Howdens units, quartz worktops, and aluminium bi-fold doors. Builder B specifies "kitchen to be confirmed" and standard uPVC patio doors. Builder A quotes £72,000. Builder B quotes £58,000.
Is Builder B cheaper? No. Builder B just hasn't priced a kitchen properly, and the doors are a different product entirely. When you equalise the spec, the real gap might be £3,000 - not £14,000.
This is why the spec section of a quote matters as much as the price. If two quotes don't specify the same materials, you're not comparing like for like. Our complete guide to what a quote should include covers exactly what to look for in the specification section.
Why the cheapest quote is often the most expensive
This sounds backwards. It isn't.
When three builders quote £68,000, £72,000, and £55,000 for the same project, most people are drawn to the £55,000. Obvious, right? Same job, less money.
Except it's almost never the same job.
The £55,000 quote is cheaper because it includes less. Maybe it excludes building regulations fees. Maybe it doesn't mention scaffolding. Maybe the scope says "kitchen to client's specification" without actually specifying anything.
Then the extras start. A £2,000 party wall agreement you didn't budget for. £1,800 for the scaffold that "wasn't in the original price." Temporary electrics. Skip hire. Suddenly your £55,000 quote is at £67,000 and climbing.
We see this pattern constantly. The cheapest quote almost always has the thinnest scope.
The missing items trap
Here's a concrete example. Imagine three quotes for a single-storey kitchen extension:
| Item | Builder A (£72k) | Builder B (£68k) | Builder C (£55k) |
|---|---|---|---|
| Foundations | Included | Included | Included |
| Structural steel | Included | Included | Included |
| Roof and insulation | Included | Included | Included |
| Windows and bi-folds | Included | Included | "Provisional allowance" |
| Kitchen supply and fit | Included (Howdens) | Included (Wren) | Excluded |
| Electrics | Included | Included | "First fix only" |
| Plumbing | Included | Included | Included |
| Scaffolding | Included | Included | Not mentioned |
| Decoration | Included | Excluded | Excluded |
| Building regs fees | Included | Excluded | Excluded |
| Skip hire | Included | Included | Not mentioned |
| Party wall costs | Excluded | Excluded | Excluded |
Builder A is expensive because they've included almost everything. Builder C looks cheap because they haven't.
When you add the missing items back to Builder C - a £8,000 kitchen, £1,500 for second-fix electrics, £1,200 for scaffolding, £800 for skips, £500 for decoration, £600 for building regs - the real cost is closer to £67,600.
Not so cheap after all. And you've now got the hassle of managing those extras yourself.
The items most often excluded
From the hundreds of quotes we've analysed, these are the items most commonly left off:
- Building regulations fees - £500–£1,000. About half of quotes exclude this.
- Party wall agreements - £700–£1,500 per neighbour. Almost always excluded.
- Structural engineer's design - £500–£1,200. Usually your responsibility to arrange.
- Scaffolding - £800–£2,500. Sometimes included, sometimes not.
- Skip hire - £250–£400 per skip, and a typical extension needs 4–8 skips.
- Decoration - final painting and decorating. Many builders stop at plastering.
- Landscaping - reinstating the garden and patio after the build.
- Kitchen or bathroom supply - some builders quote for fit-only, not supply.
- Utility diversions - moving gas mains, water pipes, or drains.
- Temporary accommodation - if the work makes the house uninhabitable.
Add these up and you're looking at £5,000–£15,000 on top of the quoted price. That "cheap" quote just got a lot more realistic. For detailed costs by project type, check our guides on kitchen extension costs, bathroom renovation costs, and loft conversion costs.
How to read the exclusions section
The exclusions section is the most important part of any quote. Seriously. More important than the total.
Good builders list their exclusions clearly. "The following items are not included in this quotation:" followed by a bullet list. That's what you want to see. It means the builder has thought about it and is being upfront.
No exclusions section at all? That's worse. It doesn't mean everything is included - it means the builder hasn't defined the boundaries. When something comes up that wasn't discussed, you'll end up in a "but I assumed..." conversation.
Read the exclusions. If an item is excluded that you expected to be covered, ask the builder to add it to the quote as a priced line item. Then you can compare properly.
When "expensive" is actually good value
Not every high quote is a rip-off. Sometimes you're paying for things that are genuinely worth more.
Comprehensive scope
A builder who itemises every trade, specifies every material, and lists clear exclusions has done more work on your quote. That time costs money. But it also means fewer surprises later.
A thorough quote protects you. A vague quote protects the builder.
Quality materials
There's a big gap between budget and premium materials:
| Material | Budget option | Premium option | Cost difference |
|---|---|---|---|
| Kitchen units | Flat-pack, laminate | Solid wood, soft-close | £5,000–£15,000 |
| Worktops | Laminate | Quartz or granite | £1,000–£5,000 |
| Windows | Standard uPVC | Aluminium slim-frame | £2,000–£6,000 |
| Flooring | Vinyl plank | Engineered oak | £1,500–£4,000 |
| Roof | Felt + mineral cap sheet | EPDM or single-ply membrane | £500–£2,000 |
A builder quoting premium materials will always look more expensive. That's not the same as being overpriced.
Experience and overheads
A builder running a proper operation - employers' liability insurance, public liability, CITB-registered workforce, a site manager - has higher overheads than a bloke with a van. Those overheads show up in the price.
But they also show up in the quality of the build, the project management, and the likelihood of it finishing on time.
A £72,000 quote from an established firm with a track record isn't the same as a £72,000 quote from someone you found on a Facebook group. Same number, very different value.
Contingency and honesty
Some builders pad their quotes slightly to cover the unexpected. Others quote lean and hit you with extras. The "padded" quote looks more expensive upfront but might end up cheaper overall.
Ask the builder directly: "Does this price include any contingency, or will variations be charged on top?" Honest builders will tell you.
Three quotes is the minimum
You've heard this before. Get at least three quotes. But here's why it actually matters.
With one quote, you have no idea whether it's high, low, or fair. With two, you know they're different but not which one's right. With three, you start to see a pattern.
If two builders quote £68,000–£72,000 and one quotes £48,000, the outlier is almost certainly missing something. If all three come in between £65,000 and £75,000, you're probably in the right range.
Three quotes also give you leverage. Not to haggle - builders hate that - but to have an informed conversation. "Your quote is £8,000 more than the next nearest. Can you walk me through what's driving the difference?" That's a fair question. The answer usually reveals either genuine added value or room to adjust.
The "day rate" red flag
Some builders quote by the day rather than the job. For small works - hanging a door, fitting a radiator - that's normal. For anything over a few thousand pounds, it's a problem.
A day rate gives the builder no incentive to finish quickly. A two-week job becomes three weeks. Three becomes four. You're paying for time, not outcomes.
For any project over £5,000, push for a fixed price. If the builder can't or won't price it, they either haven't scoped it properly or they want the flexibility to charge more.
How to sanity-check your quote in 5 minutes
Here's a quick manual process:
Step 1: Calculate the cost per m²
Total price ÷ floor area = cost per m². Compare to the benchmarks above, adjusting for your region.
If it's within 15% either side of the benchmark, you're in the right ballpark. If it's 30%+ above, ask the builder to explain what's driving the cost. If it's 30%+ below, check what's missing from the scope.
Step 2: Check the scope against the "missing items" list
Run through the 10 commonly excluded items above. Is each one clearly included, clearly excluded, or just not mentioned? "Not mentioned" is the danger zone.
Step 3: Compare material specifications
If you have multiple quotes, check whether they're specifying the same materials. "Supply and fit kitchen" vs "Supply and fit Howdens Greenwich kitchen in White" are totally different propositions.
Step 4: Look at the payment schedule
A reasonable schedule ties payments to milestones. If 50% or more is due before the roof is on, that's a red flag.
Step 5: Check validity
Is the quote still valid? Material costs move. A quote from six months ago might be 5–10% out of date.
The short version
Your builder's quote isn't "too expensive" or "too cheap" in isolation. It's only expensive or cheap relative to what's included.
A £75,000 quote that covers every trade, specifies decent materials, and lists clear exclusions might be better value than a £55,000 quote that excludes half the job.
Focus on scope first, price second.
Get a second opinion
If the numbers still don't add up, read our comparison of AI quote checkers vs quantity surveyors to decide on next steps. Or if you want to skip the manual checks entirely, upload your quote to MyBuildAlly. Our AI analyses your quote against regional benchmarks, flags missing scope items, and tells you whether the pricing looks reasonable - in about 30 seconds.
It's a lot faster than spreadsheets.