How to Get Multiple Quotes for a House Extension and Why Most Homeowners Do It Wrong
Three quotes, lowest number wins, that’s the plan almost every homeowner starts with, and it’s almost always the plan that leaves people disappointed later. Not because getting several quotes is a bad idea. It’s because most people get them before they’ve got a complete set of drawings in place, which means the three numbers they end up comparing aren’t actually comparable at all. Whether you’re searching ‘builder near me’ or specifically looking for an extension builder in Essex, the process only works properly in a particular order; get that order wrong and even a genuinely fair-looking comparison can be misleading. By the end of this, you’ll know exactly when to start getting quotes, how to make sure they’re actually comparable, and what a proper one looks like once you’ve got it in hand.
The Mistake: Getting Quotes Too Early
Here’s what typically happens. A builder walks round the garden, listens to what you’re after, and gives you a number on the spot. That number isn’t really a price; it’s a guess dressed up as one, built on assumptions about ground conditions, structure, and specification that nobody’s actually confirmed yet. Once the build starts and reality doesn’t match those assumptions, the number moves. And it’s not usually because the builder was being dishonest; they genuinely can’t know what’s involved without a structural specification, confirmed foundation depths, and a proper detailed design in front of them.
A common version of this: a builder quotes £50,000 assuming standard strip foundations. Once the ground’s actually opened up, it turns out there’s clay soil and mature trees close by, and piled foundations are needed instead. Suddenly that £50,000 is £65,000. This isn’t some rare edge case; it’s exactly what happens when builders are asked to price a project with no real information to work from.
The actual fix is simple, even if it’s not what most people expect going in: drawings first, quotes second. Only once three builders are pricing from the exact same complete technical package do the numbers actually mean something next to each other.
What You Need Before Approaching Any Builder
Four things need to be in place before any builder can give you a price worth trusting:
- Design drawings — proposed floor plans, elevations, a site plan, and a roof plan
- Planning approval or a Lawful Development Certificate, confirming the design’s actually been assessed
- Structural engineering calculations — foundation specification, steel beam sizes, floor and roof structural design (see our structural engineering page for what this actually covers)
- Building regulations drawings — the full technical package showing exactly how the extension has to be built
With all four sorted, a builder can price with genuine accuracy. Without them, they’re guessing. At Kirkwood, this whole package gets produced in-house before any builder’s ever introduced, which is exactly why the builders Kirkwood works with can quote fixed prices instead of estimates. See our design and build service for how the whole sequence fits together.
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Kirkwood manages the structural engineering stage in-house as part of its complete service.
What a Good Quote Actually Looks Like
A proper itemised quotation breaks the whole project down into its component parts, rather than handing you one number and calling it a day: groundworks, foundations, external walls, steelwork, roof structure, glazing and doors, first fix (plumbing and electrics), plasterwork, second fix, and external works. Each of those should carry its own labour cost and materials cost.
That level of detail is what actually makes comparing quotes possible. If one builder’s allowed £8,000 for steelwork and another’s allowed £4,000 for the exact same beam specification, the cheaper one isn’t cheaper; it’s incomplete. An itemised quote also means you can trim the budget by adjusting or removing specific items, rather than trying to renegotiate one lump sum from scratch. For context on what these figures should roughly look like, see our house extension costs guide.
Kirkwood’s vetted builders use quantity surveyors to put together quotations at exactly this level of detail; it’s one of the things that gets a builder recommended in the first place.
How Many Quotes Should You Get?
Three is the standard advice, enough to get a genuine feel for the market rate without turning the whole process into a second job. But three quotes only actually mean anything once every builder involved is pricing from the exact same drawings package. A 4m x 4m flat roof extension needs to be 4m x 4m in all three quotes, with matching foundation specifications, matching steelwork, and matching glazing. If the drawings don’t pin these things down precisely, the quotes won’t be comparable no matter how many you collect.
On finding builders to actually approach: word of mouth and a recommendation from a design company tend to be far more reliable than typing ‘extension builder Essex’ into Google and hoping for the best. Kirkwood introduces clients to vetted builders once the drawings package is finished, and if you’d like the fuller list of what to ask once you’re at that stage, our guide to questions worth asking a builder covers it in detail.
How to Compare Quotes Once You Have Them
Three things tend to account for almost all the variation between quotes, and each one is worth checking specifically.
- Different scope. One builder’s included bi-fold doors; another hasn’t. Go through each line item and check the specification actually matches across all three quotes.
- Different foundation assumptions. This is the single biggest source of real price variation. If the structural drawings call for piled foundations, all three quotes need to reflect that. If one quote’s noticeably cheaper, find out what foundation type they’ve actually allowed for.
- Different material quality. Glazing especially varies wildly in both price and quality. Make sure all three quotes are specifying genuinely equivalent systems, not just similar-sounding ones.
If the numbers all land close together, base the decision on track record and references, not price alone. If one’s noticeably lower than the rest, find out exactly why before you sign anything.
Getting multiple quotes is absolutely the right instinct; it only works once there’s a complete drawings package behind every number you’re comparing. Kirkwood produces that full package in-house and introduces clients to vetted builders who quote fixed, itemised prices rather than guesses.
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No, you don’t need a registered professional carrying that specific title for a house extension. What you do need is proper planning drawings, structural engineering, and building regulations drawings, and Kirkwood produces all three in-house for extensions across Chelmsford, Brentwood, Billericay, Wickford, Basildon, Rayleigh, Leigh-on-Sea, Southend, and the surrounding areas of Essex.
Frequently Asked Questions
How many quotes should I get for a house extension?
Get at least three quotes, but only once you have a complete set of drawings, structural engineering calculations, and building regulations drawings. Without these, builders cannot give accurate, fixed prices. Comparing quotes without drawings is comparing estimates, not real costs.
Why are my house extension quotes so different?
Quote variation usually comes from three sources: different scope (one builder has included items another hasn’t), different foundation assumptions (particularly common if ground conditions are unknown), and different materials specifications. If one quote is significantly lower, find out why before accepting it; it may be incomplete rather than genuinely cheaper.
Can I get a house extension quote without drawings?
A builder can give you an estimate without drawings, but not an accurate fixed price. Without structural drawings specifying the foundation depth, beam sizes, and technical requirements, any figure is based on assumptions, and assumptions change when construction begins. Getting drawings first is the only way to receive quotes you can meaningfully compare.
What should a house extension quote include?
A good house extension quote should be itemised line by line, covering: groundworks and foundations, external walls and structure, steelwork, roof structure and covering, glazing and doors, first fix (plumbing and electrics rough-in), plastering, second fix (finishing), and any external works. A single headline figure without this breakdown gives you no basis for comparison or adjustment.
What is an extension quote example?
A proper house extension quote is a detailed schedule with labour and material costs broken down by trade and stage. For a standard 4m x 4m single storey extension, it would typically run to several pages, covering each stage of the build with individual line items. Kirkwood’s recommended builders produce this level of detail as standard, prepared from the complete drawings package.
How do I find builders to quote for a house extension in Essex?
Word of mouth and recommendation from a design company are more reliable than a Google search. Kirkwood introduces clients to a hand-selected group of vetted Essex builders once the complete drawings package is in place. Each recommended builder has been assessed on their work quality, communication, and approach to pricing, and previous clients can be contacted directly.
Should I choose the cheapest house extension quote?
Not automatically. If all three quotes are based on the same complete drawings package and the lower quote is itemised and covers the same scope, it may represent genuine value. If a quote is significantly lower without explanation, ask what has been omitted or what assumptions have been made, particularly around foundations and glazing specification.
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