How to compare builder quotes properly

Three quotes for the same extension: £48,000, £61,000 and £74,000. Same drawings, same brief, a £26,000 spread. Somewhere in those documents is the real difference, and it is almost never that one builder is simply greedier than another. Comparing quotes properly means comparing what is actually priced, not the number at the bottom. Here is how to do it, and at the end, a free stage planner that does the heavy lifting for you.

Why the cheapest quote usually isn't

The cheapest quote usually isn't the cheapest because low headline prices tend to be built on thin scope, generous assumptions and exclusions that surface later as extras. Some builders under-price to win the job knowing that variations, the changes and additions agreed mid-project, are where the margin comes back. Others quote quickly and honestly but from a thinner reading of the drawings, and the gaps emerge on site either way.

The result is the same: the £48,000 job that finishes at £63,000, with every increase arriving as an awkward conversation after the work is underway and your negotiating position has evaporated. Citizens Advice (opens in a new tab) found in July 2026 that 1 in 4 homeowners had a problem with their most recent repair job, and many renovation disputes begin exactly here, in the space between what a quote said and what a homeowner understood it to say. Payment terms are part of the comparison too: whichever quote you pick, you can ask your builder to use milestone-based payment protection, so each stage is funded before it starts and released when you approve the work.

Compare like for like on scope

Two quotes can only be compared if they price the same work to the same specification. Before judging any numbers, check each quote covers the same ground:

• Itemised works. A single line saying "supply and build extension as per drawings" cannot be compared with anything. Ask for a breakdown by trade or by stage.
• Materials specification. "Flooring" is not a spec. Which brand, which grade, and is there a supply allowance? One quote including £4,000 of sanitaryware and another assuming you supply your own differ by £4,000 before anyone lifts a tool.
• The unglamorous items. Scaffolding, skips, waste removal, welfare facilities, making good, decoration. These disappear from cheap quotes first.
• VAT. Confirm whether each price includes VAT and whether the builder is VAT-registered. A 20% swing hides easily in a one-line quote.

Where a quote is silent on something the others include, ask for it to be added in writing. You are not being difficult; you are making the numbers mean the same thing.

Provisional sums and exclusions: where the real price hides

A provisional sum is a placeholder for work that cannot be priced accurately yet, and it is the most common reason a final bill leaves its quote behind. "Provisional sum for groundworks: £5,000" means nobody knows what the groundworks will cost until they dig. That is legitimate, but treat every provisional sum as a question: what happens if it is exceeded, what hourly or day rates apply to the extra, and would better investigation now, such as a trial hole or a drain survey, turn the estimate into a firm price?

Read the exclusions list with equal care. Structural steel "by others", electrical work excluded, no allowance for Building Control fees: each exclusion is a cost you will still pay, just to someone else and outside this comparison. Add excluded items back into each total before comparing anything.

Payment terms are part of the price

Payment terms tell you as much about a builder as the total does. A quote wanting a large sum upfront and vague staging afterwards is pricing in your risk; a quote built around a clear stage schedule, with each payment tied to defined completed work, tells you the builder plans the job properly and expects to be judged on delivery. Treat willingness to work through escrow as a genuine differentiator between otherwise similar quotes: a builder happy to be paid stage by stage from money held securely, as they are on platforms like Renopay, is telling you they expect to finish what they price. Terms are also where warning signs cluster, and they are worth reading alongside our guide to checking a builder and the warning signs to watch for.

Run every quote through the stage planner

Before you choose, run each quote through our free stage planner. Upload the quote and it flags missing scope, vague provisional sums, unpriced exclusions and risky payment terms in about a minute, so you can go back to each builder with specific questions rather than a general sense of unease. It is free, it does not need an account, and it turns three incomparable documents into a comparison you can actually make.

Comparing quotes well is how you choose the right builder. Paying stage by stage is how you protect the choice. Ask your builder to set it up on Renopay when you are ready to put your project on a funded milestone schedule.

Frequently asked questions

How many quotes should I get for building work?

Three is the practical standard: enough to see the market range and spot an outlier in either direction. Give each builder identical drawings and a written brief, otherwise you are buying three prices for three different jobs.

Why are builder quotes so different?

Because they rarely price the same thing. Differences in scope, materials specification, provisional sums, exclusions and VAT treatment can move a quote by tens of thousands before any difference in margin. Standardise the scope and the spread usually narrows sharply.

What is a provisional sum in a building quote?

A provisional sum is an estimated allowance for work that cannot be accurately priced yet, such as groundworks or drainage. The final cost may be higher or lower, so ask how overruns are priced and whether investigation now could firm up the number.