"How much will it cost?" is the first question everyone asks about an extension, and the honest answer is: it depends. But "it depends" is no use when you're trying to budget, so here's a straight guide to what drives the price of a house extension in Durham, and the rough ranges to plan around.
Every figure here is general guidance for 2026. The only way to know what your extension will cost is a free site visit, but this will help you work out whether your plans are realistic before you start.
Size is the obvious one, but it's not the whole story. The biggest cost drivers are the ground conditions (what's under your garden decides how much foundation work you need), the specification (a basic shell versus a high-end kitchen extension with bi-folds and underfloor heating are very different numbers), and the complexity (a simple single-storey rear extension is far cheaper per square metre than a two-storey wraparound that ties into existing roofs and drains).
Access matters too. A terrace in the city with no side access, where everything comes through the house, costs more in labour than a detached property where a digger can get to the back.
As a planning guide for 2026, a straightforward single-storey rear extension in the Durham area typically falls somewhere in the region of £2,000 to £3,000 per square metre for a good standard of finish, more for high-spec work, less for a basic shell.
A two-storey extension often works out slightly cheaper per square metre than single-storey, because you get more floor area under one roof and one set of foundations, even though the total bill is higher.
Kitchen extensions sit at the higher end once you add the kitchen itself, the glazing and the underfloor heating that people usually want.
A proper quote should cover design, structural calculations, building control, all the trades and the finishes. The things that catch people out are the extras outside the build itself: planning fees, party wall agreements with neighbours on a terrace, and upgrades like better glazing or a re-fitted kitchen that weren't in the original budget.
This is exactly why we quote fixed and in writing after a site visit, with everything itemised, so there are no surprises halfway through.
Work out your total budget, then hold back a contingency of around 10% for the unexpected, because older Durham properties in particular can throw up surprises once you open them up. Get a fixed written quote rather than a day-rate arrangement, so the risk sits with the builder, not you. And be clear about your finishes early, because changing your mind mid-build is where budgets run away.
These figures are general guidance to help you plan, not a quote. Every job is different, and the only way to know what yours will cost is a free site visit. We come out, look at the job, and give you a fixed price in writing — no call-out charge, no obligation.
As a 2026 guide, expect somewhere around £2,000 to £3,000 per square metre for a good standard, varying with ground conditions, specification and access. A free site visit gives you a fixed figure.
Usually yes, because you get more floor area for one set of foundations and one roof, even though the total cost is higher than single-storey.
Often a single-storey extension is permitted development, but conservation areas and listed buildings have tighter rules. We check this and handle any application to Durham County Council.
A typical single-storey extension runs eight to twelve weeks on site. We give a written programme before starting.
Yes, around 10% is sensible, especially with older properties that can throw up surprises once opened up.
Whatever the brief, the route in is the same: ring us, we'll visit, we'll come back with a fixed price in plain English. Free site visits across Durham, Sunderland and Newcastle.
Or email enquiries@atkinsonsgroup.co.uk
No call-out charge for quotes. Fixed prices, in writing.
