# Builder Variations Explained: What an Extra Should Cost, and What to Refuse > How extras on a London extension get priced, which ones are real, which ones were already in the quote, and how to agree them in writing before they are built. Author: Ben Murrell, Homeowners Project Manager · Published: 2026-10-09 · Category: Budgeting Canonical: https://www.homeownersprojectmanager.co.uk/blog/builder-variations-what-an-extra-should-cost A variation is a change to what the builder priced. Some are genuine. A drain is where no drawing showed a drain. You ask for a roof light that was not in the tender. The building control officer wants a lintel the engineer had not drawn. Some are the original job, re-presented as an extra once you have started and it is awkward to say no. I am Ben Murrell. I work for the homeowner, not the builder. Most of the money I save on a live job is in this pile of paper, not in a clever material substitution. ## A variation is not a conversation The expensive version happens on the doorstep. The groundworker says the foundations need to go deeper. You say fine, because four men are standing there. Three weeks later the invoice is a round number with no breakdown, and nobody can remember what was agreed. The ordinary version is dull, and that is the point. The builder writes what has changed, why, and what it costs, before it is built. You accept it, amend it, or refuse it. Then it is built. Payment follows the written extra, not the memory of the chat. A [JCT homeowner contract](https://www.homeownersprojectmanager.co.uk/blog/jct-contracts-explained-for-homeowners) gives you that mechanism. A quote does not. If you have already signed and there is no variation clause, you can still insist on the same discipline. You just have less to point at. ## What a fair extra looks like Ask for the same things you would ask for in a quote. - **What changed.** A sentence a stranger could understand. "Foundations to the side wall taken 400 mm deeper where the existing footing was higher than assumed" is a variation. "Additional works as discussed" is not. - **The measure.** Metres of trench, number of steels, hours if it is genuinely labour. A lump sum with no measure is how round numbers survive. - **The rate.** If the original quote had rates, use them. If it did not, ask where the new rate came from. A day rate that appears for the first time mid-job deserves a question. - **What it does not include.** Disposal, making good, decorating, building control re-inspection. Extras grow a second tail if those are left implied. - **The programme effect.** An extra that adds a week is not just the labour. It can be scaffolding, a kitchen that stays in boxes, and rent if you have moved out. Put that in the same note or you will meet it later as a separate claim. Provisional sums are the cousin of this problem. A provisional sum was never a price. It was an allowance. When it is spent, the difference is a variation whether anyone calls it one. I have written that up separately: [provisional sums and PC sums](https://www.homeownersprojectmanager.co.uk/blog/provisional-sums-pc-sums-builder-quotes-explained). ## What I would refuse, or send back I do not refuse extras because they are annoying. I send them back when they are not yet a price. - The item was in the drawings or the specification the builder priced. If the quote excluded it, that exclusion should have been in the quote, in writing, before you signed. - The same work appears twice. Drainage in the groundworks package, and drainage again as an extra. Making good included in the plastering line, and making good again at the end. - A percentage added to an extra for "attendance" or "profit and overhead" that was already in the rates, with no explanation. - A price that arrives after the work is done. You can still negotiate it. You have less leverage, which is why the builder waited. - Anything agreed only by text, with no measure, that is now on an invoice. None of this requires a fight. It requires the sentence: send me the breakdown before you do it. Builders who are used to working this way do not mind. Builders who are not used to it mind a great deal, which is useful information. ## Where this saves money, and where it saves the evening On the illustrations I use, a 20 m² rear extension sits around £64,000 to £84,000 ex VAT. My standard fee on that is about £7,000 to £9,200, at 11% of the project cost. One poorly described extra on foundations, drainage or glazing can be a four-figure sum. Catching two of them, or getting them priced properly, is one of the ordinary ways a fee comes back. It is not guaranteed. I say so on [the fee page](https://www.homeownersprojectmanager.co.uk/project-manager-cost). If the quote was already tight and complete, and the ground is what everyone expected, there may be little to find. The stress is the same moment. The pressure peaks when someone needs an answer and you are not sure you are allowed to say no. Client-side means that answer is my job. You still decide. You decide from a breakdown, not from a doorway with the digger idling. Anita and Simon in Fulham described it as problem-solving that saved stress and money. That is this, not a slogan. If you have a quote in front of you and you want the likely extras found before you sign, send it. That is cheaper than meeting them in week three. [Send a quote to review](https://www.homeownersprojectmanager.co.uk/contact) · 07525 474 849 · benmurrell83@gmail.com ## Keep reading - [How to compare builder quotes](https://www.homeownersprojectmanager.co.uk/blog/how-to-compare-builder-quotes) - [Payment schedule for a London extension](https://www.homeownersprojectmanager.co.uk/blog/payment-schedule-london-extension) - [Problem-solving on site](https://www.homeownersprojectmanager.co.uk/blog/problem-solving-on-site-what-a-project-manager-actually-catches) --- Homeowners Project Manager — independent client-side project management for homeowners in South West London. Contact: 07525 474 849 · https://www.homeownersprojectmanager.co.uk/contact