How Much Does a House Extension Cost in Lancashire?

What a Typical Extension Costs in Lancashire

Costs in Lancashire tend to sit a little below the national average, but there is still a wide range depending on what you are building and the finish you want. As a rough guide for a solid, builder-grade finish, not including kitchen units, bathroom fittings or furniture, expect the following.

These figures assume straightforward ground conditions and a standard brick or render finish. Add large glazing, underfloor heating or a vaulted ceiling with exposed steel, and you can easily add 15 to 25 percent onto the base figure.

• Single storey rear extension, around 4m x 5m: roughly £35,000 to £55,000
• Side return extension: roughly £25,000 to £45,000
• Double storey extension: roughly £60,000 to £100,000, since you get two rooms for one roof and one set of foundations
• Wrap-around extension: roughly £70,000 to £120,000

What Pushes the Price Up or Down

Several things move the price beyond the size of the room. Lancashire's terrain plays a bigger part than people expect. Plots on the edges of Burnley, Pendle and parts of the Ribble Valley often slope, which means more groundwork, retaining walls or extra foundation depth before a single brick goes up.

Get at least three quotes and ask each builder to break the price down by groundwork, structure, roof, and first and second fix, so you can compare like for like rather than just a bottom line figure.

• Sloping or clay ground needing deeper foundations or piling
• Matching existing stonework or brick, especially on older terraced and stone-built houses common across East Lancashire
• Structural steel beams for open-plan kitchen-diners or removed load-bearing walls
• Bi-fold doors, roof lanterns and large glazing, which cost more than they look
• Kitchen and bathroom fit-out, usually quoted separately from the build cost

Planning Permission and Building Regs Locally

Many single storey rear extensions fall under permitted development, meaning you can build without a full planning application if you stay within government size and height limits. That said, Chorley, Burnley and Pendle councils all have conservation areas, including parts around Astley Park and Euxton in Chorley, and sections of Burnley and Clitheroe, where permitted development rights are restricted and a full application is needed regardless of size.

Whichever route you take, the work still has to meet Building Regulations, covering structural calculations, insulation levels and fire safety. This is separate from planning permission and gets signed off during and after the build.

Timeline and Budgeting

A single storey rear extension typically takes 10 to 14 weeks once the diggers arrive, assuming reasonable weather and no surprises underground. Double storey and wrap-around jobs usually run to 4 to 6 months, as there is more roof, more structural work, and often a kitchen refit layered on top.

Build in a contingency of 10 to 15 percent of the total budget for anything unexpected, such as old drains, poor ground or a damp issue uncovered once work starts. Most established Lancashire builders work to staged payments tied to progress rather than asking for large sums upfront, which is worth checking before you sign anything.

Finding the Right Builder for the Job

A house extension involves several trades working in the right order: groundwork, bricklaying, roofing, electrics, plumbing and plastering. It is worth choosing a builder who manages this directly rather than subcontracting every stage and hoping it joins up. A firm based locally, used to building on Lancashire's sloping sites and matching the stone and brick common across Burnley, Chorley and Pendle, will usually give you a more realistic quote and fewer surprises once work starts.