Why three builders quote three wildly different prices

Ask three builders to price the same extension and you can receive numbers 40 percent apart. Homeowners assume someone is at it. Builders know the truth is more interesting: the three quotes are usually pricing three different jobs.

The same job is not the same job

A set of drawings looks like a fixed thing, but every builder reads it through their own experience. One assumes the existing drains can stay. One assumes they will need moving. One has been burned twice by that exact assumption and prices a full new run. None of them is wrong. They have simply resolved the drawing's silences differently, and every silence in a drawing is a decision someone has to price.

Multiply that across ground conditions, structural steel sizes, finish levels, access, and what happens to the boiler, and two honest builders can be thousands apart before anyone has thought about profit. The quotes differ because the jobs in their heads differ.

Different cost structures underneath

Even when two builders read the scope identically, their businesses cost different amounts to run. A two-man band working from a van carries almost no overhead. A firm with an office, a yard, a bookkeeper, an apprentice and proper insurance might need 15 to 20 percent on top of raw cost just to keep the lights on. Both need a margin on top of that if they intend to still exist in five years.

So the same £40,000 of labour and materials can honestly leave one builder at £46,000 and another at £54,000. The dearer builder is not greedy. They are usually the one who will still answer the phone when something needs fixing in year two. How to set and defend that number is covered in overheads and profit: setting a margin you can defend.

Different intent behind the number

The third driver is the quietest: how much each builder wants the job.

• The full diary price. A busy builder quotes high without apology. If the client says yes, the disruption is worth it. If not, nothing is lost.
• The hungry price. A builder with a gap in the schedule quotes tight to keep the team moving. Legitimate, but there is a line below which tight becomes underwater, and underwater jobs get finished badly or not at all.
• The strategic price. Some builders price keenly for the right street, the right architect, or the right kind of work they want more of.

Three sensible strategies, three different numbers, one identical extension.

The missing-items problem

There is one bad reason for a low quote, and it is the most common: something was forgotten. Scaffolding, skips, welfare, building control fees, the cost of protecting the client's floors, the two days of making good that every job needs at the end. Missed lines do not make a job cheaper, they just move the cost to an argument later, or straight out of the builder's own pocket.

What a healthy spread looks like

Across many domestic jobs, a spread of 15 to 25 percent between the lowest and highest of three quotes is normal and healthy. A quote sitting 30 or 40 percent below the others is the one to interrogate, not celebrate. Either it has read the job differently, in which case the difference should be visible in its assumptions, or it has missed things, in which case the client will pay the difference anyway, with interest and ill will.

For homeowners, the practical move is to make the comparison fair before making it at all. Give every builder the same drawings, the same spec decisions and the same list of who supplies what, then ask each of them the same question: what have you assumed, and what have you excluded? Ten minutes of that levels the field better than any amount of squinting at totals. If one quote cannot answer, that silence is itself an answer. And resist the urge to simply split the difference between the three numbers: the middle price is not automatically the honest one, the explained price is.

Closing the gap with consistency

For builders, the lesson cuts inward too. If your own quotes would come out 20 percent apart depending on which evening you priced them, the problem is method, not market. A consistent process, with the same rate book, the same prelims checklist and the same treatment of unknowns every time, is what makes your numbers defensible. It is also precisely what software is good at: QS Quoter prices from a description or drawings using your own day rates and material rates, the same way every time, and shows its working in a private tradesman copy alongside the clean client quotation. What a complete document should contain is covered in what a professional builder's quote should include, and the warning signs of a bad one in red flags in building quotes.