If you are pricing up an extension in Preston, Chorley, Leyland or anywhere else in Lancashire, you will find plenty of national figures that do not quite fit local reality. Lancashire build costs sit below London and the South East, but they have risen noticeably over the past few years. Here is an honest look at what you can expect to pay in 2026 and what actually moves the number.
Most single storey extensions in Lancashire currently come in somewhere between £1,800 and £2,500 per square metre for the build itself, finished to a standard specification. So a 20 square metre kitchen extension might land between £36,000 and £50,000 before you add VAT, professional fees and the kitchen itself. A basic specification on a straightforward plot can occasionally come in under that range, while high end finishes, structural glazing or awkward sites push it above.
Two storey extensions are better value per square metre because one roof and one set of foundations serve two floors. Expect roughly £1,500 to £2,000 per square metre across both levels, so a 40 square metre two storey addition often falls between £60,000 and £80,000. These are guide figures, not quotes. Every house is different, and a proper price only comes from a survey and a detailed specification.
The shell of the building is only part of the story. Groundworks are the biggest unknown on many Lancashire jobs, particularly on clay soils common across the county or where drains, tree roots or old foundations get in the way. If a building inspector asks for deeper footings, that cost arrives early and cannot be avoided.
How you intend to use the space matters just as much. A plain garden room is far cheaper per square metre than a kitchen extension, because kitchens bring plumbing, electrics, extraction and the units themselves. Knock through structural walls and you add steelwork, temporary supports and making good.
The builder's quote is rarely the whole bill. Architectural drawings for a typical extension cost around £1,500 to £4,000 depending on complexity, and structural engineer calculations usually add £500 to £1,200. A planning application currently costs £258 in England for a householder application, though many single storey extensions fall under permitted development and skip planning altogether. Building regulations fees to your local authority or an approved inspector typically add £500 to £1,000.
VAT at 20 percent applies to most extension work, and some price guides quote figures without it, which causes nasty surprises. It is also sensible to hold back a contingency of around 10 to 15 percent of the build cost for the things nobody can see until the ground is opened up. If you finish the job without touching it, that is a bonus, not a plan.
Comparing quotes only works if every builder is pricing the same thing. Get drawings and a written specification first, then ask two or three local firms to quote against them. A detailed, itemised quote that separates the build, the fittings and any provisional sums tells you far more than a single round number, and it makes it obvious where two quotes genuinely differ rather than simply covering different scopes.
Be cautious with any quote that is dramatically cheaper than the rest. In our experience around Preston and the wider county, a suspiciously low figure usually means something has been missed or will be added later as an extra. Ask each builder what is excluded, who handles building control sign off, and how variations will be priced if the scope changes mid job. A firm that answers those questions clearly before you sign is usually one that manages the money well once work starts.
Not always. Many single storey rear extensions fall under permitted development rights, provided they stay within size and height limits. It is worth applying for a lawful development certificate from your council so you have written proof, especially if you sell the house later.
A single storey extension usually takes 8 to 12 weeks on site, while a two storey addition often runs 12 to 16 weeks. Add a couple of months beforehand for design, approvals and scheduling, and allow slack for weather, since Lancashire winters can slow groundworks and brickwork.
Often, yes. Once you account for stamp duty, estate agent fees, legal costs and removals, moving to a larger home can cost £15,000 to £30,000 before you gain a single extra room. An extension puts that money into space you keep, though it is worth checking that the spend suits the value ceiling of your street.
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