How Much Does a Single Storey Extension Cost in Lancashire?

Typical price ranges for Lancashire homes

For a standard single storey extension in East Lancashire, most builds come out at roughly £1,800 to £2,600 per square metre. That usually covers foundations, walls, the roof, windows and doors, and a plastered finish ready for decorating. A higher spec with large glazing, vaulted ceilings or a stone finish can go past £3,000 per square metre.

Here are some rough guides, not guarantees. A small rear extension of about 3m by 4m often costs around £30,000 to £45,000. A larger kitchen and dining extension of around 20 square metres is more like £45,000 to £70,000, and that's before the kitchen itself. A new kitchen can add anywhere from £8,000 to £25,000 or more, depending on what you choose.

What pushes the cost up or down

Two extensions the same size can be priced very differently. These are the things that make the biggest difference on local jobs:

• Stone or brick: a lot of houses around Burnley, Colne and the Ribble Valley are built in local sandstone. Matching it with reclaimed or new natural stone costs more than brick or render, but the planners may expect it.
• Roof type: a flat roof with a modern membrane is usually cheaper than a pitched, tiled or slate roof tied into the existing house.
• Knocking through: opening up the back wall needs steel beams and structural calculations, which adds to both labour and materials.
• Glazing: bifold or sliding doors and roof lanterns look great but can add several thousand pounds.
• Drains: terraced and semi-detached houses often have shared drains running under the back yard. Building over them needs agreement from United Utilities and sometimes rerouting.
• Ground conditions: parts of Burnley and the surrounding area are former coal mining land. You may need a coal mining risk assessment, and deeper or specialist foundations can add cost.

The fees people forget

The building work is the biggest cost, but it isn't the only one. It's sensible to budget for these on top:

• Architectural drawings: roughly £1,500 to £4,000 depending on how complex the design is.
• Structural engineer: often £400 to £1,000 for beam and foundation calculations.
• Building control: needed for every extension, even when planning permission isn't. Fees vary by size, so check with your council or an approved inspector.
• Planning or prior approval fees: set nationally and changed from time to time, so check the current figure on your council's website.
• Party wall surveyor: if you're building on or near a shared boundary, which is common with terraces.
• Contingency: keep 10 to 15 per cent aside for surprises, especially in older houses.

Do you need planning permission?

Many single storey rear extensions fall under permitted development. That generally means up to 3m deep on a terraced or semi-detached house and 4m on a detached one, as long as height and materials limits are met. Under the larger home extension scheme you can go deeper, up to 6m or 8m, but you need prior approval from the council first.

Conservation areas, listed buildings and homes where permitted development rights have been removed are different. Burnley, Pendle, Hyndburn and Ribble Valley all have conservation areas, so check with your local planning department before you commit to a design. Whatever the planning position, Building Regulations approval still applies.

Getting a quote you can rely on

Get at least two or three quotes and make sure they're priced on the same drawings and spec. Ask what is included and what isn't. Things like plastering, electrics, flooring, the kitchen and skip hire are often where quotes differ.

Look out for provisional sums, which are allowances for items not yet confirmed, such as foundations. A low quote with big provisional sums can easily end up costing more than a higher quote with everything fixed. A good builder will go through these with you and tell you plainly where the risks are.