My Builder Is Asking for More Money Than the Quote — What Are My Rights?

The job is nearly finished. The kitchen looks great. Then your builder hands you a bill that is £4,000 more than the price you agreed. "Materials went up." "The plumbing was more complicated than I thought." "You asked for those extra shelves, remember?"

This happens more often than it should. It is one of the most common disputes in domestic building work, and it almost always comes down to one thing: what was actually agreed, and whether it was a quote or an estimate.

Quote vs estimate: the legal difference

This distinction matters because it determines your rights.

A quote is a fixed price for a defined scope of work. It is legally binding. Once you accept a quote, the builder must complete the work for that price. If the job costs them more than they expected — materials go up, the work takes longer — that is their risk, not yours. They cannot come back and charge more unless the scope of work changes.

An estimate is an educated guess at what the work might cost. It is not fixed. The final bill can be higher or lower. However, it should be within a reasonable range of the estimate. If the builder estimated £8,000 and the final bill is £9,000, that may be reasonable. If it is £14,000 with no clear explanation, you have grounds to challenge it.

The first thing to check: did you receive a quote or an estimate? Look at the original document. If it says "quote" or "quotation," the price is fixed. If it says "estimate" or "approximate cost," it is a guide. For a detailed explanation of the difference, see our guide on quote vs estimate: which protects you.

What the law says

Under the Consumer Rights Act 2015, services provided to you must be carried out with reasonable care and skill. If you hired a tradesperson to do a job for a quoted price, and they are now demanding more without a legitimate reason, that is a breach of the agreement.

The key question is whether the scope changed. If you asked for extras during the job — a different tile, additional sockets, a bigger shower — those are variations. The builder is entitled to charge for them. But variations should be agreed in writing before the work is done, not presented as a surprise on the final bill.

If the builder is charging more because they underestimated the work — they did not account for the pipework being complicated, or the plastering taking longer — that is their problem, not yours. A quote means the builder assessed the work and committed to a price. That commitment stands.

What to do step by step

1. Ask for a detailed breakdown

Before you refuse to pay or escalate, ask the builder for an itemised breakdown of the extra charges. What specifically costs more than quoted? When was the additional work done? Was it requested by you or discovered by the builder?

Sometimes the breakdown reveals a genuine misunderstanding. The builder may have done work they assumed was included in your request but was not in the original scope. Or you may have asked for something on site that you have since forgotten about. The breakdown clarifies what happened.

2. Check what was agreed

Go back to the original quote or estimate. What exactly was included? What was the price? Were there any terms about additional charges or variations?

If you have a written contract, this is straightforward — the scope is documented. If you relied on a verbal agreement or a WhatsApp message, it is harder. This is one reason why a written contract matters so much.

3. Identify what you did and did not agree to

Separate the extra charges into two categories:

• Things you asked for: If you requested additional work during the project — even verbally — the builder may have a reasonable claim for extra payment. The question is whether the price was agreed before the work was done.
• Things you did not ask for: If the builder did additional work without your knowledge or agreement, you are not obliged to pay for it. A builder cannot unilaterally expand the scope and then charge you for the expansion.

4. Put your position in writing

Send an email or letter to the builder. Be specific:

• Confirm the original quoted price
• Acknowledge any extras you did agree to (and the price, if agreed)
• Dispute any charges for work you did not agree to
• State the amount you are willing to pay

Keep the tone factual, not confrontational. You are documenting your position, not starting a fight. This letter becomes important evidence if the dispute goes further.

5. Pay what you owe, dispute what you do not

If part of the bill is undisputed — the original quoted work was completed satisfactorily — pay that amount. Withholding the entire payment when only part of the bill is in dispute puts you in a weaker position. For more detail on how much you can reasonably withhold, see our guide on withholding payment for poor workmanship.

What if the builder threatens legal action?

If you have been reasonable — you paid for the agreed work and only disputed charges that were not authorised — you are on solid ground.

Most builders will negotiate rather than go to court. Court is slow, expensive, and uncertain for both sides. Small claims court (for disputes under £10,000) does not require a solicitor, but it does require evidence.

The evidence that matters:

• The original quote or estimate
• Any written agreement about extras (texts, emails, contract amendments)
• Photos of the work
• Your correspondence disputing the charges
• Proof of what you have paid

If you have a clear written record of what was agreed, your position is strong. If everything was verbal, it is harder — but a builder who quoted verbally and then demands significantly more will struggle to convince a judge that the higher amount was agreed.

Real examples of how this plays out

Consider a kitchen renovation quoted at £18,000. Halfway through, the builder says the plumbing is more complicated than expected and presents an additional bill for £3,500. If the original quote clearly included "all plumbing work to new kitchen layout," the builder is responsible for that cost — they should have assessed the plumbing before quoting. The complexity was foreseeable, and the risk sits with the builder.

Now consider a different scenario. The same kitchen renovation, same quote. During the project, you decide you want the island moved to the other wall and underfloor heating added. The builder prices these as extras — £2,200 for the island relocation and £1,800 for the heating. These are legitimate variations. You changed the scope, and the builder is entitled to charge for the additional work. The question is whether you agreed to the price before the work was done.

The grey area is where the builder did extra work that you sort of asked for but never formally agreed a price. "Can you tile behind the fridge as well?" said on site at 9am becomes a £400 charge on the invoice. You thought it was a five-minute favour. The builder thought it was a variation. Without a written agreement, it is your word against theirs.

The pattern in almost every dispute is the same: something was agreed informally, nobody wrote it down, and both sides remember a different conversation. A written contract with a variation clause prevents the entire argument.

How to prevent this on your next project

The best way to avoid this situation is to have a proper written contract before work starts. A good contract includes:

• A clear scope of work — what is and is not included
• A fixed price for that scope
• A variation clause — any changes must be priced and approved in writing before work begins
• A payment schedule tied to milestones, not a single lump sum at the end

With a contract like this, the "can my builder charge more?" question answers itself. The price is what was agreed. Any changes go through the variation process. There are no surprises at the end — only decisions you made along the way, each one documented and approved.

For the tradesperson's perspective on the quote-vs-estimate decision, see our guide for tradespeople on which to give their customers.

The bottom line

If your builder quoted a fixed price, they must honour it. If they estimated, the final cost must be reasonable. Either way, extras should be agreed in writing before the work is done.

Before your next project starts, ask your builder if they use a contract app. If they use TradeContract, you will have everything agreed in writing before a single brick is laid. Learn more.