Get a realistic cost estimate for your build before you commit
For homeowners, self-builders, landlords and developers who need a reliable budget. Compare quotes from quantity surveyors and cost consultants who can estimate build costs, prepare cost plans and check builders’ prices.
A cost estimate tells you what your project is likely to cost to build before you spend heavily on design or sign a contract. It is usually prepared by a quantity surveyor or cost consultant, who measures the work from drawings, applies current rates for labour and materials in your area, and lists the fees, VAT, contingency and exclusions that a builder’s price won’t show. Early on, it tests whether your plans and your budget match. As the design develops it becomes a cost plan, updated at each stage, and later it gives you a benchmark to check builders’ tenders and changes against.
How a professional can help
- Early budget estimate: From sketches or a written brief, they give an early estimate so you can see whether the size, specification and budget of your project fit together before design fees mount up.
- Cost plan as the design develops: They break the cost down by element, such as foundations, structure, roof, windows, services and finishes, and update it as drawings progress so overspends are spotted before tender.
- Value engineering: When the estimate is over budget, they suggest changes to materials, construction methods or scope that reduce cost while keeping what matters most to you.
- Pre-tender estimate and tender checks: Before builders price, they prepare an estimate to compare against, then check returned tenders for errors, missing items and rates that look unusually high or low.
- Bills of quantities: On larger projects they measure every item of work so all builders price identical quantities, which makes tenders directly comparable and later changes easier to value.
- Valuations and final account: During the build they can value work done, price variations and agree the final account with the builder, so the end cost is checked rather than simply accepted.
Is this right for you?
- You have an idea or early drawings and want to know whether your budget is realistic before going further.
- You’re a self-builder or developer and need a cost plan for a lender, an investor or a development appraisal.
- Builders’ quotes for your project are far apart and you want an expert view of what the work should cost.
- Your design has come in over budget and you need practical ways to bring the cost down without losing what matters.
- You disagree with a builder about the value of extras or the final bill and want it checked independently.
How the project usually runs
- Brief and information review: The quantity surveyor reviews your drawings, specification, site details and budget, and confirms what the estimate will cover, including fees, VAT and contingency.
- Initial estimate: Using floor areas, the type of construction and current market information, they prepare an early estimate with its assumptions and exclusions stated, to test the brief against your budget.
- Elemental cost plan: As your designer develops the drawings, the estimate is broken into building elements and updated at each design stage, with any overspend flagged alongside options to correct it.
- Pre-tender estimate: Once technical drawings and the specification are complete, a detailed estimate or bill of quantities is prepared, giving a benchmark before builders are asked to price.
- Tender checks and cost control: Builders’ prices are compared against the estimate, and if you keep the surveyor on, they value payments and changes during the build through to the final account.
What affects the cost
- How developed the design is, since detailed drawings allow a more thorough and reliable estimate than early sketches.
- Whether you need a single estimate, a cost plan updated at several design stages, or a full bill of quantities.
- The size, type and complexity of the building, including basements, major structural alterations or historic fabric.
- Whether the appointment carries on into the build, covering valuations, variations and the final account.
- Whether a lender, investor or monitoring surveyor needs formal cost reports, and how often.
Approvals and rules that affect your budget
- Building Regulations set standards for energy efficiency, ventilation, fire safety and more, which shape the specification and the cost. The requirements differ between England, Scotland, Wales and Northern Ireland.
- Planning conditions can add costs, and in England and Wales so can Section 106 obligations and the Community Infrastructure Levy, where some exemptions must be claimed before work starts.
- VAT isn’t the same for every project: new homes and some conversions can qualify for zero or reduced rates, while most extensions are standard-rated, so check HMRC’s rules or ask a tax adviser.
- Building control charges, utility connections, specialist reports and, in England and Wales, any party wall surveyors’ fees are real costs a complete estimate should list, though they sit outside the builder’s price.
Questions people ask
How accurate is an early cost estimate?
It can only be as reliable as the information behind it. An estimate based on sketches carries more uncertainty than one based on detailed drawings and a specification, so it should state its assumptions, its exclusions and a contingency for the unknown. Expect it to be refined as the design develops, and treat an early figure as a guide rather than a promise.
Why not use a price per square metre from the internet?
Rates published online are averages that can’t reflect your property, your area, your ground conditions, your specification or the current market. They often leave out fees, VAT, demolition, drainage or external works. A quantity surveyor builds an estimate from your actual project, so you can see what drives the cost and where savings could be made.
What’s the difference between an estimate and a builder’s quote?
An estimate is an independent forecast of what the work should cost, prepared for you. A builder’s quote or tender is an offer to do the work for a price, on terms that suit the builder. Having an estimate first means you can tell whether quotes are reasonable, spot missing items and ask informed questions.
Does a cost estimate include VAT and professional fees?
It should say clearly. A complete project budget usually covers the build cost, VAT, professional and statutory fees, surveys, utility connections and a contingency. Some estimates cover the construction cost only, so check what’s included before comparing figures or using one for a loan application.
Do I need a quantity surveyor for a home extension?
Not always. On smaller projects your designer or builder may give a reasonable budget figure. A quantity surveyor is most useful when the budget is tight, the project is large or unusual, a lender needs a cost report, or builders’ quotes are hard to compare. Many will provide a one-off estimate rather than a full appointment.
Can a quantity surveyor help if the final bill is higher than expected?
Yes. They can review the variations, provisional sums and claims the builder has priced, compare them with the contract and the instructions given, and help you agree a fair final account. They can’t change the terms you signed, so the earlier they’re involved, the more they can help.
Available across the UK
Professionals cover the whole of the UK: England, Scotland, Wales and Northern Ireland. Planning and Building Regulations differ between the four nations, and your professional will work to the rules that apply where your property is.