If you are pricing up an extension in Poole, you will find quotes vary wildly, and it is hard to know what a sensible budget looks like. This guide sets out realistic cost ranges for single and double storey extensions in the local area, explains what actually drives the price, and flags the costs people most often forget.
For a straightforward single storey extension in Poole, most homeowners should budget somewhere between £2,200 and £3,000 per square metre for the build itself, to a decent standard of finish. That means a modest 20 square metre rear extension typically lands between £45,000 and £60,000 before VAT, fees and fitting out a kitchen or bathroom. Higher specification work, structural glazing or awkward access can push it beyond that.
Double storey extensions work out cheaper per square metre because the roof and foundations are shared across two floors. Expect roughly £1,800 to £2,500 per square metre, so a 40 square metre two storey addition might come in between £75,000 and £100,000. These are guide figures, not quotes; the only reliable number is a detailed, itemised price based on drawings for your specific property.
Ground conditions matter more in Poole than people expect. Parts of the town, particularly nearer the harbour and low lying areas around Hamworthy and Oakdale, can have soft or waterlogged ground that needs deeper foundations, and that is dug and priced only once trial holes or building control inspections confirm what is down there. On sloping plots around Constitution Hill or Lilliput, retaining work and stepped foundations add cost too.
The other big variables are glazing, roof design and what goes inside. Bifold or sliding doors, roof lanterns and vaulted ceilings all add thousands each. A new kitchen in an extension can easily add £15,000 to £30,000 on its own. Access is worth thinking about as well: tight Victorian terraces in Heckford Park or Branksome cost more to build behind than a detached house in Broadstone with side access for machinery and skips.
The build price is not the whole budget. Architectural drawings typically cost £1,500 to £4,000 depending on the size and complexity of the project, and structural engineer calculations usually add £500 to £1,500. If you need planning permission from BCP Council rather than building under permitted development, the application fee is a few hundred pounds, and building regulations fees generally run £500 to £1,000 plus.
You may also need a party wall agreement if you are building close to a neighbour's boundary, which is common on Poole's semi detached and terraced streets; surveyor costs can range from a few hundred pounds to over £1,000 per neighbour if they appoint their own surveyor. Finally, VAT at 20 percent applies to most extension work, so always check whether a quoted figure includes it.
Get drawings done first, then ask two or three builders to price the same specification. Quotes are only comparable if they are pricing the same thing, so a written spec covering foundations, glazing, heating, electrics and finishes matters more than the headline number. Be wary of a quote that is dramatically cheaper than the others; it usually means something has been left out that will reappear later as an extra.
Hold back a contingency of at least 10 percent, agree a payment schedule tied to completed stages rather than large sums up front, and confirm who is responsible for building control sign off. A good local builder will be happy to walk you through their quote line by line and show you comparable projects they have completed nearby.
Not always. Many single storey rear extensions fall under permitted development rights, subject to size and height limits, though it is worth getting a lawful development certificate from BCP Council for peace of mind. Larger, double storey or side extensions, and homes in conservation areas, will usually need a full planning application.
A typical single storey extension takes around 10 to 14 weeks on site, while a double storey extension is usually 4 to 6 months. Add several months before that for design, planning and building regulations approval, so allow the best part of a year from first sketch to finished room.
Often, yes. With Poole house prices well above the national average, moving costs including stamp duty, agent and legal fees can swallow tens of thousands of pounds, whereas a well built extension adds usable space and usually adds value to your home. It depends on your street and how much you spend, so it is worth checking local sold prices before committing.
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