Getting a straight answer on extension costs is harder than it should be. This guide lays out realistic figures for Preston and the surrounding Lancashire area, explains what shifts the price, and helps you budget before you ever speak to a builder.
As a working guide, expect somewhere between £1,800 and £2,800 per square metre for a good-quality single storey rear extension in the Preston area. A typical 4m by 5m (20 square metre) extension therefore tends to land between roughly £36,000 and £56,000, before VAT where it applies.
Preston sits a little below central London and southern rates, which is good news, but labour and material costs have risen sharply since 2021. Be wary of any quote well under £1,500 per square metre; it usually means corners will be cut or the price will creep up later.
Two extensions of identical size can differ by £15,000 or more. The biggest swings come from the roof type, the amount of glazing, and how much of the internal fit-out is included in the figure you are quoted.
Ground conditions matter locally too. Parts of Preston, Fulwood and Penwortham have clay or made-up ground that can call for deeper or reinforced foundations, and any nearby trees or drains can trigger extra design and cost.
The headline build figure is rarely the full story. Planning and Building Control fees, structural design and party wall matters all sit on top and can add a few thousand pounds overall.
Many single storey extensions in Preston fall under permitted development and need no full planning application, but you will still need Building Regulations approval. If you share a wall or boundary with a neighbour, a Party Wall Agreement may also be required.
Ask every builder to quote against the same written specification, otherwise you are comparing figures that include different things. A cheaper number that excludes the kitchen, flooring and decorating is not actually cheaper.
Look for a clear payment schedule tied to stages of work rather than a large sum up front, and confirm what happens if unforeseen issues appear once the ground is opened up. A good local builder will talk you through the realistic range rather than promising a suspiciously precise figure over the phone.
Most single storey extensions take around 10 to 16 weeks on site, depending on size and complexity. Weather, structural steel and bespoke glazing lead times can extend that.
Many rear extensions fall under permitted development, so no full planning application is needed, but this depends on size, your property type and whether you are in a conservation area. You will still need Building Regulations approval either way.
Yes. Keeping the shape simple, choosing a flat roof over a lantern, and reusing the existing kitchen layout all trim cost while keeping the build sound. Doing your own decorating at the end is another sensible saving.
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