Single Storey Extension Costs in Lancashire: A Real Guide

Typical costs per square metre in Lancashire

As a working rule for 2026, a straightforward single storey extension in Lancashire tends to come in between £1,800 and £2,400 per square metre for a standard specification. That means a modest 15 square metre kitchen extension might sit somewhere around £27,000 to £36,000 for the build itself, while a larger 30 square metre wraparound could reach £55,000 to £75,000 once you factor in a higher finish.

Lancashire prices are generally kinder than the South East, where the same job might cost 30 to 40 percent more. Even so, no honest builder will quote from a phone call alone. Ground conditions, access, and what you want inside the room all matter, which is why these figures should be treated as a starting point rather than a promise.

What actually drives the price up or down

Two extensions of identical size can differ by £20,000 or more, and the reasons are usually hidden in the detail rather than the floor area. The biggest swings come from groundworks and glazing. Much of East Lancashire sits on clay, and some plots near older mill terraces have made ground or shallow drains, so foundations occasionally need to go deeper than the standard one metre.

Kitchens and bathrooms are the other big variable. A plastered shell with sockets and radiators is one price; a fully fitted kitchen with an island, underfloor heating and bifold doors is quite another. It helps to separate the build cost from the fit out in your own budget so you can see where the money is going.

• Foundations: deep or reinforced footings can add £3,000 to £8,000
• Glazing: bifold or sliding doors typically add £1,500 to £4,000 over standard patio doors
• Roof type: a flat roof with a lantern usually costs more than a simple pitched roof
• Knock through: removing a structural wall and adding a steel beam adds roughly £1,500 to £3,500
• Moving drains or a soil stack: budget £1,000 to £3,000 if pipework runs where you want to build

The costs beyond the builder's quote

The build price is not the whole story. Most single storey extensions in Lancashire fall under permitted development, but you will still need Building Regulations approval, and many people choose a lawful development certificate for peace of mind when selling. Architect or architectural technician drawings for a single storey project typically run from £1,200 to £3,000 locally, with structural engineer calculations adding £400 to £900.

Building control fees through your local authority, whether that is Burnley, Hyndburn or Ribble Valley, usually total £500 to £900 for a project of this size. If your plans need full planning permission, the householder application fee is around £258. Add a sensible contingency of 10 to 15 percent of the build cost, because once the ground is opened up, surprises are possible even on well surveyed plots.

How to get an accurate price and keep control of it

Ask for itemised quotes rather than a single figure. A good quote separates groundworks, structure, roof, glazing, first and second fix, and finishes, which makes it far easier to compare builders like for like and to spot where one quote is quietly excluding something another includes.

Be wary of a price that is dramatically lower than the others. In our experience it usually means something has been missed, whether that is scaffolding, skips, or making good the existing house where new meets old. A written schedule of payments tied to completed stages, rather than large sums up front, protects both sides and is standard practice for reputable Lancashire builders.

• Get at least three itemised written quotes from local firms
• Confirm who handles Building Regulations applications and inspections
• Agree stage payments in writing before work starts
• Check the quote states whether VAT is included
• Ask what is excluded, such as flooring, decorating or the kitchen itself