Why do renovation quotes differ so much?
Quotes for the same job can be thousands of pounds apart, and that usually does not tell you who is too expensive. It tells you the quotes do not promise the same thing: scope, provisional sums, labour rates and materials spec. Four causes, all four checkable, and a fair way to compare.
The four real causes
- 1. Scope: they are not pricing the same job
- One quote includes strip-out, waste removal, making good and project management; the other leaves them out or says "by others". This is the biggest source of difference and the easiest to check: put the quotes side by side and mark every line that appears in only one of them.
- 2. Provisional and PC sums: uncertainty as a number
- A low provisional sum or PC sum makes a quote look cheap while the risk moves to you. Comparison is only possible once the sums are levelled: the same PC sums for tiles and sanitaryware and the same provisional sum for the unknowns in every quote.
- 3. Labour rates and busyness
- Rates differ per trade, per region and per order book. A firm with a full diary quotes high; that is market forces, not a rip-off. VAT registration can add up to 20% between otherwise similar firms.
- 4. Materials specification
- Without an agreed spec, one firm prices budget materials and another mid-range. On a bathroom the tile choice alone can move the total by thousands; agree the level, or make one quote assume the same products as the other.
On the third of those, the published rate guides disagree with each other and in places with themselves, so a labour figure in a quote is harder to judge than it looks. The day rates overview shows the full spread per trade, and why the days matter more than the rate.
How to compare them fairly
- Same description, same lines.
- Ask every builder to quote against the same written description, and mark the lines that appear in only one quote.
- Level the provisional sums.
- Ask what each sum is based on and what happens if it is exceeded.
- Put an independent range next to the totals.
- The quote check gives a verdict per quote: below, within or above the guide range for your project, region and finish.
- Question the outliers.
- Both the cheapest and the dearest should be able to point at the lines that explain their difference. If they cannot, that is your answer.
The classic trap is choosing on the total alone: a single lump sum without itemised lines makes checking impossible and makes changes expensive later. Always ask for an itemised quote with quantities and unit prices; a professional who resists that rarely does so without a reason.
No quotes yet? Know your range first with the free cost calculator, and plan the money side with how to pay for a renovation; paying per completed stage is your best protection whatever the quotes say. Chosen a builder? Nail the agreement down with the contract checklist before you sign.
Frequently asked questions
Why do quotes for the same job differ by thousands of pounds?
Four causes explain nearly every gap: the quotes do not cover the same work (scope), uncertain items are entered as provisional sums or PC sums that shift the risk to you, labour rates and how busy each firm is differ per trade and region, and the materials specification differs. A big gap usually means you are comparing apples with pears, not that someone is dishonest. Make the quotes comparable first, then judge them against an independent range.
What is a provisional sum, and what is a PC sum?
Two different allowances. A provisional sum is money set aside for work that cannot yet be described in enough detail to price, such as repairs nobody can see until the floor is up. A PC (prime cost) sum is a supply-only allowance for materials or goods whose exact quality is not chosen yet, such as tiles at so much per square metre; fitting them is priced separately.
That is how the RICS measurement rules define them (NRM 2, rics.org, read 27 September 2026). Either way, if the real cost comes out higher, you pay the difference. Two quotes with different allowances cannot be compared until you level them: ask what each sum is based on and what happens if it is not enough.
Is the cheapest quote suspicious?
Not automatically, but a price far below both the other quotes and an independent range is a warning sign rather than a bargain. Common explanations: missing scope (waste removal, making good, scaffolding), a tight provisional sum, or the job was simply misread. Ask before you sign.
Is the most expensive one a rip-off?
Also not automatically. A full order book, employed staff rather than subcontractors, longer guarantees or a more complete scope can explain a higher price. The difference just has to be visible in the lines of the quote, not in vague words.
How many quotes should I get?
Three is the practical standard: enough to see the spread, few enough to read each one properly. Ask all three to price the same written description, otherwise you build the first difference in yourself.
Does VAT explain quote differences?
Sometimes. A VAT-registered firm must charge VAT, at the standard 20% on most work, while a trader who is not VAT-registered cannot charge it (registration is compulsory above £90,000 turnover and voluntary below it), so for the same work the registered firm can come out up to a fifth higher (gov.uk, VAT registration, VAT rates and Charge, reclaim and record VAT, read 27 September 2026).
Check whether each quote says including or excluding VAT before you compare anything else; an "ex VAT" total next to an "inc VAT" total is a fifth of the price in hidden difference.