Can a Builder Charge More Than the Quote?

You've accepted a builder's quote, work has started, and then the number goes up. Sometimes it's a fair variation. Sometimes it's a quote that was never really fixed. Knowing the difference before you sign, and mid-job if the bill starts climbing, is what this guide is for.

This is practical guidance from a builder's point of view, not legal advice. For a dispute, speak to a solicitor or Citizens Advice.

Quick answer

• On a fixed-price quote for a defined scope, the builder should not charge more for that same work unless you agree a change (a variation) in writing.
• They can charge more if the scope changes, if you ask for extras, if provisional or PC sums are spent above the allowance, or if the document was only an estimate.
• "I found more once we opened it up" is sometimes genuine. It still needs a written price before the extra work is done.
• Before you sign: pin down scope, exclusions, VAT, provisional sums and how variations are priced.
• Mid-job: do not keep paying for undefined extras. Pause, get the change in writing, then decide.

If the quote already feels open-ended, send it over before you pay a deposit. For £59 I'll read up to three quotes for one job and tell you which parts are fixed. Review my builder's quote, £59

When a builder can charge more

1. The document was an estimate, not a fixed quote

An estimate is a best guess. The final bill can be higher. If your paperwork says "estimate", or mixes the words, treat the total as provisional until you have a clear fixed quote for a defined job. More on quote vs estimate and whether a builder's quote is legally binding.

2. You changed the scope (variations)

Extra sockets, a different kitchen, thicker insulation, moving a doorway: all of these change the cost. A fair process is:

1. You ask for the change (or the builder spots a need).
2. The builder prices it in writing.
3. You agree the price before the work is done.
4. The variation is added to the contract.

If work is done first and priced later, you have lost your leverage. That is how bills climb.

3. Provisional sums and PC sums get spent

A provisional sum is an allowance, not a fixed price. If the quote has £4,500 for foundations "as required" and the real cost is £7,200, you usually pay the difference (plus any agreed margin). Same idea for PC (prime cost) sums on fixtures. See provisional sums and PC sums explained.

4. Exclusions you did not notice

Decorating, flooring, making good next door's side, building control fees, spoil removal, or connecting to drains are often left out. They are not "extras" in the builder's mind; they were never in the price. Compare quotes with the free builder quote comparison tool so gaps show up early.

5. Unforeseen conditions (sometimes)

Rot behind a wall, buried concrete, contaminated spoil, or foundations that have to go deeper than anyone could see without opening up: these can be genuine. A careful quote either allows for investigation, uses a provisional sum, or says what happens if conditions differ. A one-line lump sum with no exclusions and no process is where arguments start.

When they should not just "add it on"

• The same scope, same materials, same access, and a document that said fixed quote or quotation.
• Day-work rates billed for work that was already in the fixed price.
• Materials marked up again when they were already in the quote.
• Charging again for preliminaries that were already priced for the programme you agreed.
• Raising the price because the builder under-priced the job.

Under-pricing is the builder's commercial risk on a fixed price, not yours, provided the scope did not change.

Fixed-price contract, still getting extras

If you signed a fixed-price agreement (or accepted a fixed quote with clear terms):

1. Ask for a written breakdown of every extra: what changed, why, and the price.
2. Compare each item to the original scope and exclusions.
3. Refuse to pay for work that was clearly included.
4. Agree or reject each variation in writing before more work happens.
5. Keep paying only for completed stages that match the original schedule, while the dispute is sorted.

If the relationship has already broken down, see our example builder dispute and get advice early. Paying under pressure "just to keep them on site" often makes the hole deeper.

What to lock down before you sign

• Quote or estimate, clearly labelled
• Full scope and a clear exclusions list
• Materials specified, not "or similar"
• VAT stated (included, plus, or not registered)
• Every provisional and PC sum listed with how it will be finalised
• Payment schedule tied to finished stages, deposit in the 5-10% band
• Written variations process
• How long the price is valid

The full walk-through is in how to check a builder's quote.

Already mid-job and the bill is climbing? Send the original quote, the variations and the latest request. For £59 I'll tell you what looks like a fair change and what does not. Review my builder's quote, £59

Contingency is your buffer, not theirs

Hold your own contingency (typically 10% of build cost, or 15% for pre-war). That is money you control for genuine unknowns. It is not a licence for the builder to spend without agreement. More in how much contingency to hold for building work.

The short version

A fixed quote for a defined job should hold. Price rises need a change in scope, a spent allowance, or an estimate that was never fixed. Agree variations in writing before the work. If the paperwork is vague, fix it before you pay a deposit, not after the walls are open.

Want a builder to read the quote before the number moves?

I've been a builder for nearly 30 years. For £59, send me up to three quotes for one job. I'll tell you which parts are fixed, which are allowances, and what to pin down before you sign. Written review and a call within 24 hours. I never quote for the work and take no referral fees.

Review my builder's quote, £59 · See an example review · Free quote comparison tool