How Much Does a House Extension Cost in Lancashire?

A house extension in Lancashire typically costs between £1,500 and £2,800 per square metre in 2026, depending on the type of extension, the quality of finish and the complexity of the build. That puts a standard single-storey rear extension at roughly £30,000 to £55,000 for most homeowners in the Burnley, Colne and surrounding areas.

These figures are lower than the national average because labour rates and material costs in East Lancashire are more competitive than London and the South East, where the same project would cost 30 to 50 percent more.

This guide breaks down the real costs by extension type so you can plan with confidence before speaking to a builder.

Extension costs at a glance

Here's what homeowners in Lancashire can expect to pay in 2026 for the most common extension types, based on a standard quality finish with good materials.

Single-storey rear extension (15–25m²): £30,000 to £55,000
Double-storey extension (30–50m²): £55,000 to £120,000
Side return extension (8–15m²): £20,000 to £40,000
Wraparound extension (25–40m²): £50,000 to £90,000
Garage conversion: £8,500 to £20,000
Loft conversion: £27,500 to £65,000

All figures include labour and materials at 2026 rates. VAT, professional fees and planning costs are additional unless stated.

What affects the cost of an extension?

No two extensions cost the same. These are the factors that move the price up or down.

Size. The biggest single factor. More square metres means more foundations, more walls, more roofing and more finishing. A 3m x 5m extension at £2,000 per m² costs £30,000. A 5m x 6m extension at the same rate costs £60,000.

Complexity. A simple rectangular rear extension is straightforward. Add bifold doors, structural steelwork, vaulted ceilings or unusual roof shapes and the price climbs. Every non-standard element adds both material and labour cost.

Finish quality. Standard tiles, basic kitchen units and carpet will cost less per square metre than underfloor heating, handmade tiles and solid oak flooring. The difference between a standard and premium finish can be £500 to £1,000 per square metre.

Ground conditions. In parts of East Lancashire, particularly in areas like Rossendale and Pendle, sloped sites or poor ground conditions can require deeper foundations or specialist groundwork. This adds cost that's hard to predict without a survey.

Access. If your property has limited side access or the site is difficult to reach with machinery and materials, expect higher costs. Terraced properties in towns like Burnley, Nelson and Colne often face this challenge.

Existing structure. Older properties, particularly stone-built terraces common across Lancashire, can require more preparation and structural work than modern builds.

Single-storey extension costs

The most popular type of extension for homeowners across Lancashire. A single-storey rear extension adds living space at ground level, usually extending the kitchen, dining area or living room.

Cost per m²: £1,500 to £2,800
Typical project cost (20m²): £30,000 to £55,000
Build time: 10 to 14 weeks

Most single-storey extensions in the Burnley and Pendle area fall between £35,000 and £50,000 for a standard quality finish. This includes foundations, walls, roof, electrics, plumbing, plastering, flooring and decoration.

Kitchen or bathroom fit-outs are additional. A full kitchen installation adds £8,000 to £25,000 on top of the build cost depending on the quality of units and appliances.

Double-storey extension costs

A double-storey extension adds space on two floors. The cost per square metre is often slightly lower than building two single-storey extensions separately because the foundations and roof are shared.

Cost per m²: £1,800 to £3,000
Typical project cost (40m²): £70,000 to £120,000
Build time: 14 to 20 weeks

Double-storey extensions almost always require a full planning application. They also need structural engineering for the additional load, which adds professional fees.

For homeowners in Lancashire considering a double-storey, the economics are strong. With average house prices in Burnley sitting at around £129,000 in 2026, a well-executed double-storey extension can add significant value, particularly when adding a bedroom with an en-suite, which research from Nationwide Building Society estimates adds up to 23 percent to a property's value.

Loft conversion costs

Loft conversions are an alternative to extending outward. They use existing roof space to create additional rooms, typically bedrooms or home offices.

Velux (rooflight) conversion: £27,500 to £40,000
Dormer conversion: £35,000 to £55,000
Hip-to-gable conversion: £40,000 to £65,000

Many terraced and semi-detached properties in East Lancashire have good loft potential. The height of the existing ridge, the pitch of the roof and the position of existing water tanks all affect feasibility. A survey is essential before committing.

Garage conversion costs

Converting an existing garage into a living space is typically the most affordable way to gain an additional room.

Cost: £8,500 to £20,000
Build time: 3 to 6 weeks

Garage conversions rarely require planning permission and are usually completed under building regulations only. They're popular in areas like Colne, Clitheroe and the Ribble Valley where many properties have attached or integral garages.

Additional costs to plan for

The build cost is the largest expense, but it's not the only one. These costs are often missed in early budgets.

Planning application: £258 for a standard householder application in England (2026 fee).

Structural engineer: £550 to £2,500 depending on the complexity.

Architectural drawings: £1,500 to £4,000 for full design and planning drawings.

Building regulations: £400 to £900 for a building control application.

Party wall agreement: £700 to £1,500 per neighbour if your extension is within three metres of a shared wall.

Contingency: Budget 10 to 15 percent for unexpected costs. Older properties in particular can reveal hidden issues once work begins.

Do you need planning permission?

Many single-storey extensions in Lancashire can be built under permitted development rights, meaning no formal planning application is required.

Under current rules, you can build a single-storey rear extension up to 4 metres deep on a detached property, or 3 metres on a semi-detached or terraced property. Under the larger home extension scheme, this extends to 8 metres (detached) or 6 metres (semi/terraced), subject to a neighbour consultation process.

Permitted development rights do not apply to listed buildings, properties in conservation areas or Areas of Outstanding Natural Beauty. Several areas across the Ribble Valley and Pendle fall within these designations, so always check with your local planning authority before starting.

Two-storey extensions almost always require full planning permission.

Is it worth extending in Lancashire?

For most homeowners in East Lancashire, extending is significantly cheaper than moving. When you factor in estate agent fees, stamp duty, legal fees, removal costs and the stress of moving, a well-planned extension often delivers better value.

With the average house price in Burnley at around £129,000 in 2026, an extension costing £40,000 to £50,000 represents a major investment relative to the property's value. That makes it important to plan carefully and ensure the extension adds proportional value rather than over-capitalising.

Extensions that tend to add the most value include additional bedrooms with en-suites, open-plan kitchen and dining areas, and ground-floor living space with good natural light.

How we can help

We deliver extensions and conversions across East Lancashire, from single-storey rear extensions to full double-storey builds. Every project includes clear pricing, regular updates and a process designed to keep you informed from first visit to final handover.

If you're considering an extension and want to understand what's realistic for your property and budget, get in touch. We'll visit your home, discuss your ideas and provide a clear quotation with no obligation.