How to check a builder's quote before you sign

Most builder's quotes are written to win work, not to protect you. A vague scope of works benefits the contractor — anything not explicitly included becomes a potential extra charge once work has started and you have no easy way to walk away. Research consistently shows that construction disputes arise most frequently not from quality issues but from scope disagreements — the client believed something was included, the contractor believed it wasn't. A well-specified quote prevents this before it starts.

Before you look at the price or the scope, check that the contractor holds the required certifications for the work being done. In the UK, certain types of work are legally restricted to registered operatives. For heating and gas work, your contractor must be Gas Safe registered. Ask for their Gas Safe registration number and check it on the Gas Safe Register website. For oil boiler installations, they must hold OFTEC registration. For unvented hot water cylinders, they must hold a G3 qualification. Work carried out by an unregistered operative is not just poor practice — it is illegal, voids your building insurance, and may need to be redone at your cost. For electrical work, ask for their Part P certification. For window installations, check whether they hold FENSA registration or whether Building Regulations notification will be needed. A professional contractor will list their certifications on their quote without being asked. If they don't, ask — and be cautious if they're reluctant to provide them.

Read every line of the quote and ask yourself: is this complete? For any trade, there are items that are frequently omitted from quotes and then charged as extras once work starts. For all types of work, check whether the quote includes: removal and disposal of all existing materials and waste, making good all surfaces disturbed during the works, protection of surrounding areas during the works, and attendance on any inspections required. For heating and plumbing: check whether the quote includes all pipework modifications, electrical work for controls and thermostats, Building Regulations notification, and system commissioning and testing. For extensions and structural work: check whether the quote includes structural engineer's calculations if required, Building Regulations application and fees, groundworks and drainage, and any temporary works needed. For each item that isn't mentioned, estimate what it would cost if added mid-project. This gives you a realistic picture of the true cost if you sign the quote as presented.

Certain phrases in building quotes are red flags — they transfer financial risk to you or create opportunities for additional charges. Here are the most common ones to watch for. "Subject to site conditions" means the price can change once work starts, at the contractor's discretion. Ask them to specify exactly which conditions might affect the price and by how much. "Allow for" means the item is a provisional sum — an estimate rather than a fixed price. Any provisional sum in a quote should be queried and, where possible, converted to a fixed price before you sign. "Excluding unforeseen works" is reasonable to a point, but ask them to define what they mean by unforeseen and what the process would be for agreeing any additional costs before work proceeds. "Daywork rates apply for extras" means any additional work will be charged at an hourly rate — which the contractor has an incentive to maximise. Get the daywork rates in writing and ensure there is a process for agreeing the scope of any extra work before it is carried out. "Subject to planning approval" means the contractor won't proceed if planning is refused — reasonable — but check whether any deposit or fees are refundable in this event.

Assessing whether a builder's quote is fair requires knowledge of current market rates for the specific type of work in your area. Prices vary significantly by region, by specification, and by the time of year. A price that looks too good to be almost certainly means one of three things: significant items are excluded and will appear as extras, the specification is lower than you expect, or the contractor has made a mistake and will try to recover it during the works. Be particularly cautious of prices that are significantly lower than other quotes you have received. Get at least three quotes for any significant work and treat any outlier — high or low — with extra scrutiny. When comparing quotes, make sure you are comparing like for like. A cheaper quote that excludes waste disposal, making good, and Building Regulations notification may actually be more expensive in total than a higher quote that includes everything.

Before signing any quote, get written confirmation of the following: What exactly is included and excluded from the price? Ask for a complete list of exclusions in writing. What certifications do you hold that are relevant to this work? Ask for registration numbers. Will you handle all Building Regulations notifications and inspections, and is this included in your quoted price? What is your payment schedule and what are the terms for any deposit? Do you carry public liability insurance and professional indemnity insurance? Ask for certificates. What is your process if unforeseen issues are discovered? How will additional costs be agreed before work proceeds? What warranty do you offer on your work, and is it backed by an insurance-backed guarantee? How long will the work take and what happens if you overrun? Get all answers in writing before you sign. A contractor who is reluctant to confirm anything in writing is a significant warning sign.

Most homeowners read the quote, look at the price, and sign if it seems reasonable. Very few ask for written confirmation of every item before signing, and even fewer get a second opinion on whether the quote is complete. The cost of getting an independent review of a significant quote — whether through a professional QS or an AI tool — is trivial compared to the cost of discovering mid-project that your quote was missing £8,000 of work that you now have to pay for.