7 Quoting Mistakes UK Builders Make That Cost Real Money

Most builders don't lose money because they're bad at their trade. They lose money because of avoidable mistakes in how they price the job. Here are the seven most common quoting errors — and how to fix them.

1. Using Old Material Prices

You quote a job in January using the prices you paid in November. By the time you start in March, one or more material prices have moved and the quoted allowance no longer covers the order.

Fix: Pull current supplier prices at the point of quoting, record the date and validity period, and use contract wording appropriate to how later price changes will be handled. Do not assume every material category moves at the same rate.

2. Underestimating Labour

For example, if you estimate 10 days and the work takes 14, four days of labour were not allowed for. At an illustrative fully loaded labour cost of £300 per day, that is a £1,200 estimating gap. Use your own labour cost rather than treating that figure as a market day rate.

Fix: Track your actual labour time on every job — not just total days, but by trade/phase. After 6 months you'll have your own real productivity rates based on your team's actual performance, not industry averages.

3. Not Including Your Overheads

Your van costs money. Your tools need replacing. Insurance, phone, accounting software, fuel, and administration are real business costs even when they do not appear as obvious job line items.

The right overhead recovery figure depends on your actual annual costs, billable capacity, and job mix. If it is absent from pricing, direct job costs may be covered while the business still loses money.

Fix: Calculate your annual overhead costs (van, insurance, tools, software, fuel, professional fees). Divide by your annual working days. Add a daily overhead recovery figure to every job you price.

4. Forgetting Provisional Sums

You start groundworks and find the soil is heavy clay — three times more expensive to break up and remove than the sandy topsoil you assumed. You hit a drain that wasn't on any survey. You open a wall and find timber frame where you expected block.

These conditions can occur but should not be presented as certain. If the quote relies on an unverified assumption, state it clearly and explain how a change will be valued.

Fix: Use a clearly described provisional sum only where part of the work cannot yet be defined or priced. Base the amount on the known risk and show how the final adjustment will be calculated; a generic allowance on every job can create false confidence.

5. Not Charging for Variations

The client asks for small changes throughout the job. You do them. You don't charge for them because each one feels too small to raise an invoice for. By the end of the job, you've done 20+ unpaid "small" tasks that add up to days of uncharged labour.

Fix: Have a written variation procedure in your contract. Issue a variation notice for every change — even minor ones. If you do this consistently from the start, clients expect it and accept it. If you start charging partway through a job, it creates friction.

6. Quoting Too Quickly Without a Site Visit

A client sends you a WhatsApp message with photos and asks for a quote. You estimate £35,000. You arrive on site and immediately see three problems you couldn't see in the photos — a chimney breast that complicates the roof structure, a conservatory that needs to come down first, and a shared drain that will require a party wall agreement.

Fix: Never quote a job from photos or a brief description alone. If a full site visit isn't possible before the quote, build in a large contingency and clearly state what you haven't been able to assess. Better to lose a quote than to win a job you lose money on.

7. Quoting Net Without Thinking About VAT

If you're VAT registered, your client pays 20% VAT on top of your quoted price. That's fine — but problems arise when you're not clear in your quote about whether prices include or exclude VAT.

A client who agreed to a £40,000 extension quote and then receives an invoice for £48,000 will feel misled — even if you were technically correct. That's a relationship-damaging moment that can lead to disputes, delayed payment, and bad reviews.

Fix: Every quote should clearly state whether prices include or exclude VAT and the rate applied. HMRC says most work on existing houses and flats is standard-rated at 20%. Zero-rating and the reduced 5% rate apply only when specific conditions are met, such as qualifying new dwellings or certain qualifying conversions and renovations. Check VAT Notice 708 or obtain professional advice before applying an exception.

The Common Thread

These mistakes are easier to catch with a repeatable review process. A structured estimate, clear assumptions, written variations, and live cost comparison reduce the risk of omissions and make developing overruns visible sooner.

QuoteBuild gives small UK builders that system without the weight of enterprise software. Start your free trial and see how it changes the way you quote.

If these mistakes show up in your own quotes, see how the process works or compare plans.

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