Builder quotes vary because builders often price different jobs, even when they use the same drawings. One builder may include tiles, paint and a new kitchen. Another may leave them out. The best way to compare quotes is to check what each builder has included, left out and guessed. Do not compare the total price alone.
Here is a simple example. You ask three builders to price an extension. The quotes come back at £60,000, £75,000 and £90,000. That gap feels huge. But it often has a simple cause. The builders did not all price the same work. (These numbers are made up to show the point.)
We have more than 35 years of experience in design and build. In that time, we have seen this problem again and again. Homeowners compare totals. They should compare what is inside each total.
Good drawings make quotes much easier to compare. Our architectural and design services help you set out what you want before you ask anyone for a price.
The Real Reasons Builder Quotes Differ
Most of the gap comes from what each builder has assumed. These are the usual causes:
- Scope. This is the list of jobs the builder will do. One quote may include the whole project. Another may stop at the shell.
- Spec. This is the list of materials and finishes, such as windows, floors and lights. A basic window costs less than a high-quality one.
- Labour. Builders guess how many workers they need and for how long. They also differ on which trades they include.
- Allowances. These are set amounts for things that are not yet decided. We explain them below.
- Site work. Poor access, soft ground or scaffolding can add cost. Some builders include these. Some do not.
- Overheads. These are the running costs of the business, such as insurance, office costs and managing the job.
- Exclusions. These are jobs the builder has left out on purpose.
- VAT. One quote may include it. Another may not.
Picture two builders with the same extension drawings. The first builder reads them with a full spec. It covers insulation, windows, floors, electrics, heating, painting and outside work. The second builder prices the building work only. The homeowner must arrange the rest. The second quote looks cheaper. But it is not the same job.
This matters a lot on a house extension, because small spec changes can change how much work is needed. Before you ask for prices, you may want to read about our home extension services so you know how design and build works.
What a Good Quote Should List
A good quote shows how the builder plans each part of the job. Look for these items:
- Groundworks and foundations
- Steel beams
- Brickwork and outside finishes
- Roofing
- Windows and outside doors
- Insulation
- Plumbing and heating
- Electrics
- Plastering
- Flooring
- Painting and decorating
- Kitchen or bathroom
- Scaffolding
- Waste removal
- Site management
- Building Control
- Specialist subcontractors
- Professional fees
- Provisional sums
- Prime cost sums
- VAT
- Exclusions
The clearer these items are, the easier it is to compare one quote with another.
How to Compare Builder Quotes Step by Step
You do not need special skills. A simple side-by-side check works well.
- Give every builder the same drawings and the same list of materials. If they start with different facts, they will give different prices.
- Ask for an itemised quote. One big total hides too much.
- Put the quotes in a table. List each job in a row and each builder in a column.
- Mark the gaps. If one quote has no flooring, note it.
- Ask each builder to price the gaps. Then you can compare fair totals.
- Ask about big differences. A good builder will explain them clearly.
- Check the small print. Look at VAT, the payment plan, the start date and how long the price stays valid.
Why the Cheapest Quote May Not Be the Best Value
A low quote is not always a bad one. A builder may have lower costs or a smarter way of working. But a big gap needs an answer.
The problem is not that a builder is cheaper. The problem is not knowing why.
If one quote is far below the others, ask the builder to explain. It may be a fair business choice. Or it may mean they read the job in a different way. Look closely at these areas:
- Materials. Are the products the same, or are they of equal quality?
- Labour. Has the builder allowed for every trade the job needs?
- Finishes. Are floors, paint and fittings included?
- Outside work. Is drainage, paving or tidy-up work included?
- Professional needs. Are design, engineering and Building Control clearly covered?
Do not judge a builder on price alone. Think about experience, how well they talk to you, the quality of past work, the timetable and how clear the contract is. A slightly higher quote can be better value if it covers more of the job and gives you more certainty.
Remember, you pay a builder for more than labour. You pay for skill, planning, materials, managing other trades, insurance, safety, quality checks and the duty to finish the agreed work. Two builders can have different costs and still give honest quotes.
Red Flags in Cheap Quotes
A very cheap quote needs a closer look. Do not reject it straight away, and do not accept it straight away either. Watch for these signs:
- Vague words. Phrases like “complete extension” or “all works included” sound nice. They do not tell you what has been priced. A good quote gives enough detail for you to see the builder’s plan.
- “By others.” If a quote says some jobs are “by others”, ask who will arrange and pay for them. A builder does not have to do every job. But you should know who does what before you sign.
- Hidden exclusions. Exclusions are not always bad. A clear list of them makes a quote more open. The risk is when big jobs are left out quietly and you think they are covered.
- Low allowances or “to be confirmed”. These can make a quote look cheap now and cost more later.
Provisional Sums and Prime Cost Sums
These two terms confuse many homeowners. Here is what they mean.
A provisional sum is a set amount for work that cannot be priced yet. For example, the builder may not know what the ground is like. So they put in an amount for now. The real cost may be higher or lower.
A prime cost sum, or PC sum, is a set amount for an item you have not chosen yet. Tiles, taps and kitchen units are common examples.
RICS guidance explains the same split. Provisional sums cover parts of the work that are not fully designed. PC sums cover items where the final choice has not been made. RICS gives a carpet as an example. The cost of the carpet can be a PC sum, while the cost of fitting it is usually fixed. At the end, the gap between the PC amount and the real price changes the final bill.
Here is a simple example with made-up numbers. A quote has a PC sum of £30 per square metre for tiles. You choose tiles that cost £60 per square metre. You will pay the extra £30 for every square metre.
If the ground is unknown, a provisional sum can be fair. The key question is what the amount covers and how the final cost will be worked out. Ask the builder:
- What work does the provisional sum cover?
- Why is it provisional?
- What would help price it more exactly?
- How will changes be priced?
- Who must approve extra work?
Low PC sums need care. They can make a quote look good, then cost you more when you pick real products. Make sure the amount fits the quality you want.
VAT: Check That Every Quote Uses the Same Basis
Always check if VAT is in the price. A quote of £50,000 plus VAT is not the same as £50,000 with VAT included. At 20%, the first one comes to £60,000.
HMRC’s VAT notice for buildings and construction explains the rules. Most building work on an existing home is charged at 20%. Some work is charged at 5% or 0%. Examples include some home conversions and some new homes. The rate depends on the type of job and your situation.
So do not guess. Ask each builder to state the VAT rate and say why it applies. If you are unsure, check with HMRC or a tax adviser.
Fixed Price, Estimate or Day Rate
These three terms mean different things. Know which one you are agreeing to.
Fixed price. The builder agrees a price for a set list of work. This gives you more certainty. But it does not mean nothing can change. Changes you ask for, provisional sums and surprises on site can still alter the final bill. It depends on the contract.
Estimate. An estimate is the builder’s best guess. It is useful early on to see if a project is possible. It is not the final price.
Day rate. You pay for the builder’s time at an agreed daily rate. This can suit small or unclear jobs. Ask how materials, subcontractors and equipment will be paid for.
For bigger projects, a clear list of work and a written agreement matter even more.
Get a Written Contract
The Planning Portal says many homeowners draw up a building contract at the start of a home improvement job. It can set out how and when you pay, the insurance details and the dates for finishing. It also gives you a point to measure the work against as the project goes on.
Read the contract before you sign. Make sure it matches the quote.
How We Write Our Quotes at Tacman Developers
At Tacman Developers, we start by learning what you want. Then we give you clear details of the work we plan to do. Our aim is simple. You should know what is included, what is left out and what is still to be decided before building starts.
A clear quote should answer these questions:
- What is being built?
- Which materials and finishes are expected?
- Which jobs are included?
- Which jobs are left out?
- Which items are still provisional?
- Who is responsible for each part?
This matters most on a full home renovation, where many trades must work together. The same goes for a new home. If you are planning one, see our new-build service to learn how design, spec and building fit together. Tacman Developers Ltd is registered in England (company number 15303945).
[ADD: one or two real details from your own work, such as a time when a clear quote avoided a problem on site, or a common item that builders leave out.]
Conclusion
Quotes differ because builders may price different work, not just because one is dear and one is cheap. They may use different specs, different scopes or different guesses about what you will supply.
To compare fairly, give every builder the same drawings and specs. Check each item that is in and out. Understand provisional and PC sums. Confirm the VAT. Read the contract before you decide.
Do not choose a builder on the lowest number alone. Look at how complete the quote is. Look at their experience, how well they communicate, the quality of their work and how they manage a project.
We believe homeowners should know exactly what they are agreeing to before building starts. Whether you plan an extension, a refurbishment, a loft conversion or a new home, a clear scope and an open quote give you a strong start. If you want to talk about your project, contact the Tacman Developers.
Frequently Asked Questions
Why do builder quotes vary so much in the UK?
Builders use different specs, labour plans, materials, allowances and exclusions. The key is to check that each builder has priced the same work.
Should I always choose the cheapest builder quote?
No. The cheapest quote may be good value. But it may also leave out work or use low allowances. Compare the full scope before you decide.
What should a building quote include?
A good quote explains the work, materials, labour, allowances, exclusions, VAT, payment terms and any other key assumptions.
What is a provisional sum?
A provisional sum is a set amount for work that cannot be priced yet. The final cost may change once the real work is known.
What is a prime cost sum?
A prime cost sum is a set amount for an item you have not chosen yet, such as tiles. Check whether fitting costs are included.
Why are exclusions important in a builder’s quote?
Exclusions are jobs the builder has left out. If you know them, you will not assume they are covered.
Should VAT be included in a builder’s quote?
The quote should say whether VAT is included and which rate is used. HMRC rules depend on the type of building work and your situation.
How many builder quotes should I get?
There is no fixed number. Three is a common choice, and it helps you see the market and spot big gaps. Give each builder the same information.
What should I do if one builder is much cheaper?
Ask the builder to explain the gap. Then compare what is included, left out and allowed for in each quote. Do not decide on the headline price alone.
