How Much Does a House Extension Cost in Burnley?

Typical extension costs in Burnley and East Lancashire

As a broad guide for 2026, a straightforward single storey extension in the Burnley area typically works out somewhere between £1,700 and £2,400 per square metre for the build itself. That means a modest 4m x 4m rear extension often lands in the £28,000 to £40,000 range, while a larger 6m x 4m kitchen extension might run from £42,000 to £60,000 once you allow for glazing, finishes and connecting into the existing house.

A double storey extension usually costs less per square metre than you might expect, often £1,500 to £2,000, because the roof and foundations are shared across two floors. A typical two storey side or rear extension adding a kitchen below and bedroom above commonly falls between £55,000 and £85,000. These figures are guides rather than quotes, because the condition of your existing house, ground conditions and your choice of finishes all move the number.

• Small single storey (around 12 to 15 sqm): roughly £25,000 to £38,000
• Larger single storey kitchen extension (20 to 25 sqm): roughly £40,000 to £60,000
• Double storey extension (30 to 40 sqm total): roughly £55,000 to £85,000
• Garage conversion as a cheaper alternative: often £12,000 to £20,000

What pushes the price up or down

The biggest single factor is what happens below ground. Plenty of Burnley housing stock is Victorian or early twentieth century terraced and semi detached property, and older drains, shallow foundations or made up ground can add several thousand pounds before a wall goes up. If a public sewer runs close to the extension, a build over agreement with United Utilities adds cost and time.

The next factor is specification. A basic extension with standard bifolds, a plastered finish and a mid range kitchen is a very different job from one with structural glazing, underfloor heating and a full knock through with steel beams. Opening up the back of the house into one large space typically needs steelwork designed by a structural engineer, which adds design fees and installation cost but is often what makes the project worthwhile.

• Groundworks, drains and foundations, especially on older terraced plots
• Steelwork for open plan knock throughs
• Glazing choices, since large sliders or roof lanterns add thousands
• Kitchen and bathroom fit outs, which can rival the shell cost
• Access, as tight terraced streets can slow deliveries and skips

Costs beyond the build itself

Alongside the build cost, allow for professional fees and approvals. Architectural drawings for a typical extension cost around £1,200 to £3,000, structural engineer calculations £400 to £900, and Burnley Borough Council charges for a planning application if you need one, currently a few hundred pounds for a householder application. Many rear extensions fall under permitted development, but it is worth confirming before you commit, particularly on corner plots or previously extended houses.

Building regulations approval and inspections are required whether or not you need planning permission, so budget for those fees too. It is also sensible to hold a contingency of around 10 to 15 percent of the build cost. On older Lancashire properties the surprises tend to appear when floors come up or walls are opened, and a contingency means those moments are an inconvenience rather than a crisis.

Getting quotes and comparing them fairly

When you gather quotes, make sure each builder is pricing the same thing. A detailed drawing and specification lets everyone quote like for like, which is why the cheapest headline figure is sometimes the most expensive job by the end. Ask what is included: does the price cover the kitchen, decoration, flooring and external landscaping, or just the watertight shell?

A reputable local builder should be happy to show you extensions they have completed nearby, explain their payment schedule, and confirm they carry public liability insurance. Staged payments tied to completed work are normal; large upfront deposits are a warning sign. If a quote is dramatically lower than the others, ask what has been left out rather than assuming you have found a bargain.