Not sure how to get a construction estimate in the UK — or whether the one you've received is any good? This complete guide covers every step: what information to prepare, what a professional estimate should include, how much it costs, and how to avoid the mistakes that blow budgets.
Getting a construction estimate is the single most important step before committing to any building project in the UK. Whether you're planning a rear extension, a loft conversion, a new build, or a commercial development, an accurate estimate tells you whether your project is financially viable — and protects you from the budget overruns that derail thousands of UK construction projects every year.
But many homeowners, developers, and even experienced contractors don't fully understand how to get a construction estimate, what it should include, or how to tell a good one from a bad one. This guide covers everything you need to know — from the information you need to prepare, to how to use your estimate to negotiate with contractors and protect your budget.
What Is a Construction Estimate?
A construction estimate is a detailed, professional assessment of what a building project should cost. It's produced by a qualified estimator or quantity surveyor who analyses your drawings, specification, and site conditions to calculate the cost of every element of the work — from foundations to final decoration.
A construction estimate is not the same as a contractor's quote. A quote is a price that a specific contractor is willing to do the work for. An estimate is an independent, unbiased view of what the work should cost at fair market rates. The difference matters enormously when you're evaluating contractor tenders.
Think of it this way: if you were buying a second-hand car, you'd want to know its market value before negotiating with the seller. A construction estimate does the same job for your building project — it tells you what fair value looks like, so you can negotiate from a position of knowledge rather than guesswork.
Step 1: Gather the Information You Need
The quality of your construction estimate is directly tied to the quality of information you provide. The more detail you can share upfront, the more accurate and reliable your estimate will be. Here's what to prepare before approaching an estimating service or contractor.
- Drawings or sketches — even a rough hand-drawn sketch is better than nothing; planning drawings or architect's drawings give the most accurate results
- Site address — location affects labour rates, material delivery costs, and access constraints
- Specification level — standard, mid-range, or high-end finishes? The difference can be 50–100% on the total cost
- Structural requirements — any known ground conditions, existing building constraints, or structural engineer's reports
- Programme — when do you need the work completed? Tight programmes can add 10–20% to costs
- Specialist requirements — underfloor heating, smart home systems, bespoke joinery, solar panels, EV charging
- Planning status — do you have planning permission, or is the project still at feasibility stage?
- Any known risks — contaminated land, protected trees, party wall obligations, listed building status
You don't need full planning drawings to get a meaningful estimate. Even a rough sketch and a clear description of what you want to build is enough to produce a useful indicative cost. Many clients commission an early estimate during feasibility to check viability before investing in detailed design.
Step 2: Choose the Right Type of Estimate
Not all construction estimates are the same. The right type of estimate depends on the stage of your project and the level of detail you need. Here's a breakdown of the main types:
- Indicative / feasibility estimate: Produced from sketch designs or early concepts. Accuracy typically ±15–25%. Used to check whether a project is financially viable before investing in detailed design. Usually produced within a few hours.
- Cost plan: Produced from planning drawings and a specification. Accuracy typically ±10–15%. Used for budget setting, funding applications, and early contractor negotiations. Usually produced within 24–48 hours.
- Bill of quantities (BoQ): A detailed, fully measured document produced from construction drawings. Accuracy typically ±5–10%. Used for competitive tendering — contractors price against the same document, making quotes directly comparable. Usually takes 3–7 days.
- Tender estimate: A detailed estimate produced to check contractor tenders. Used to identify overpriced or suspiciously low bids. Usually produced within 24–48 hours.
For most domestic projects — extensions, loft conversions, refurbishments — a cost plan is the right choice. For larger commercial projects or any scheme going to competitive tender, a full bill of quantities is worth the additional investment.
Step 3: What a Professional Estimate Should Include
A professional construction estimate is far more than a single number. It should break down costs by trade and element so you can understand exactly where your money is going and make informed decisions about where to save or spend more.
Here's what every professional construction estimate should include:
- Preliminaries — site setup, welfare facilities, scaffolding, project management, insurance
- Substructure — excavation, foundations, underground drainage, ground floor slab
- Superstructure — structural frame, external walls, roof structure and covering
- External envelope — windows, external doors, cladding, rendering
- Internal finishes — plastering, ceilings, internal doors and joinery, flooring, decorating
- Mechanical and electrical — heating system, plumbing, electrical installation, ventilation
- External works — landscaping, driveways, fencing, external drainage
- Contingency allowance — typically 5–15% depending on project risk and stage of design
- Professional fees — architect, structural engineer, planning consultant (if not already appointed)
- VAT — most construction work is subject to 20% VAT (some exceptions apply)
Always check whether VAT is included in the estimate. Many estimates show costs exclusive of VAT — adding 20% to a £100,000 project is a £20,000 surprise you don't want at the end.
Step 4: How to Get a Construction Estimate in the UK
There are three main ways to get a construction estimate in the UK. Each has its advantages and disadvantages depending on your project type and budget.
- Professional estimating service (recommended): A specialist firm like Page Building Consultants produces an independent, detailed estimate from your drawings and specification. Fast, accurate, and unbiased. Costs £150–£600 for domestic projects. Gives you a benchmark to evaluate contractor quotes against.
- Quantity surveyor: A qualified QS can produce a full bill of quantities for competitive tendering. More comprehensive than a standard estimate, and essential for larger commercial projects. Costs more but provides greater accuracy and contract management support.
- Direct contractor quotes: Getting quotes directly from contractors is free, but you have no independent benchmark to evaluate them against. You can't tell whether a quote is fair, overpriced, or dangerously low without an independent estimate to compare it to.
The most effective approach for most projects is to get an independent professional estimate first, then use it to evaluate contractor quotes. This takes the guesswork out of the process and puts you in a much stronger negotiating position.
How Much Does a Construction Estimate Cost in the UK?
For most domestic projects, the cost of a professional estimate is recovered many times over through better contractor negotiations and avoided budget overruns. If an independent estimate helps you identify that a contractor's quote is £15,000 too high, the £300 you spent on the estimate has paid for itself 50 times over.
At Page Building Consultants, we offer competitive fixed-price estimating services for projects of all sizes. Call us on 0800 688 9321 or submit your drawings online to get a quote for your specific project.
- Indicative / feasibility estimate (domestic): £150–£300
- Cost plan from planning drawings (domestic extension or loft conversion): £250–£500
- Full bill of quantities (domestic new build): £400–£800
- Cost plan (commercial project up to £500k): £500–£1,500
- Full bill of quantities (commercial project £500k–£2m): £1,000–£3,000
- Full bill of quantities (commercial project £2m+): £2,000–£8,000+
How Accurate Is a Construction Estimate?
Even the most detailed estimate can't account for everything. Ground conditions, unforeseen structural issues, and changes to the scope of work can all affect the final cost. This is why a contingency allowance is essential — and why the contingency should be larger at early design stages when uncertainty is highest.
A professional estimator will clearly identify the assumptions made in producing the estimate and flag any areas of significant uncertainty. If an estimate doesn't include this information, treat it with caution.
- Sketch design / feasibility stage: ±15–25% accuracy — useful for checking viability, not for setting a firm budget
- Planning drawings stage: ±10–15% accuracy — suitable for budget setting and funding applications
- Construction drawings stage: ±5–10% accuracy — suitable for competitive tendering
- Full bill of quantities: ±3–7% accuracy — the most accurate pre-construction cost assessment possible
A 10% contingency is the minimum for any construction project. At early design stages, or on projects with significant groundworks or structural unknowns, 15–20% is more appropriate. Never treat a contingency as money you expect to spend — it's insurance against the unexpected.
How to Use Your Estimate to Evaluate Contractor Quotes
Once you have an independent estimate, you're in a powerful position to evaluate contractor quotes. Here's how to use it effectively:
- Compare like for like: Make sure the contractor's quote covers the same scope as your estimate. Missing items are the most common cause of post-contract disputes.
- Check the breakdown: A professional contractor should be able to provide a breakdown of their quote by trade. If they can't or won't, that's a red flag.
- Investigate outliers: If a quote is more than 15% above or below your estimate, find out why. It might be a legitimate difference in specification or programme — or it might be an error or deliberate omission.
- Don't automatically choose the cheapest: A quote that's 20% below the market rate is almost always missing something. The cheapest quote often becomes the most expensive project.
- Check what's excluded: Most contractor quotes include a list of exclusions. Read these carefully — they often include items like scaffolding, structural engineer's fees, or making good after trades.
- Negotiate from knowledge: Use your estimate to negotiate. If a contractor's quote is 10% above the estimate, you have a factual basis for asking them to sharpen their price.
Common Mistakes When Getting a Construction Estimate
These are the mistakes we see most often — and they're all avoidable with a little preparation.
- Providing insufficient information: The less detail you provide, the less accurate the estimate. Always share as much information as possible.
- Not specifying the specification level: "Standard" and "high-end" can mean a 50–100% difference in cost. Be specific about the finishes you want.
- Ignoring VAT: Most construction work is subject to 20% VAT. Always check whether your estimate includes VAT or not.
- Forgetting professional fees: Architect, structural engineer, and planning consultant fees can add 10–15% to your total project cost.
- Underestimating contingency: A 5% contingency is not enough for most projects. Budget 10–15% minimum.
- Treating an estimate as a fixed price: An estimate is a professional assessment of likely cost — it's not a guarantee. Costs can change if the scope changes or unforeseen issues arise.
- Not getting an independent estimate before approaching contractors: Without an independent benchmark, you have no way of knowing whether contractor quotes are fair.
- Choosing the cheapest quote without understanding why it's cheap: Low quotes are often low for a reason — missing scope, poor quality materials, or an inexperienced contractor.
The single most expensive mistake you can make is starting a construction project without an accurate budget. The cost of getting it wrong — abortive work, contractor disputes, project stalls — is always far greater than the cost of getting a professional estimate upfront.
Construction Estimate Costs by Project Type (2026)
To give you a practical reference point, here are typical construction estimate ranges for the most common project types in the UK in 2026. These are mid-range specification costs, excluding VAT and professional fees, for projects in the Midlands or North of England. London and South East add 20–35%.
- Single-storey rear extension (4m x 5m): £38,000–£62,000
- Double-storey rear extension: £65,000–£110,000
- Loft conversion (dormer): £38,000–£62,000
- Loft conversion (Mansard, London): £85,000–£130,000
- Garage conversion: £15,000–£35,000
- Full house refurbishment (3-bed): £60,000–£120,000
- New build detached house (150m²): £270,000–£420,000
- Commercial fit-out (office, per m²): £800–£2,500/m²
- Commercial new build (shell and core, per m²): £2,000–£3,500/m²
These are indicative ranges only. Your actual project cost will depend on the specific design, site conditions, specification, and programme. Always get a project-specific estimate before committing to a budget.
How Page Building Consultants Can Help
Page Building Consultants has been providing professional construction estimates and quantity surveying services across the UK for over 38 years. Our team of qualified quantity surveyors and estimators has worked on projects ranging from £10,000 domestic extensions to £150 million commercial schemes.
We offer a fast, accurate, and competitively priced estimating service for projects of all sizes. Most domestic project estimates are turned around within 24 hours of receiving your drawings and specification. For larger commercial schemes, we'll agree a turnaround time when you submit your enquiry.
Our estimates are fully itemised by trade and element, clearly identify assumptions and exclusions, and include a risk register highlighting any areas of significant uncertainty. We can also provide a tender evaluation service to help you assess contractor quotes once you've received them.
To get a construction estimate for your project, call us on 0800 688 9321 or use our online contact form. We cover the whole of the UK and can typically arrange a call to discuss your project within a few hours of your enquiry.