If you are pricing up an extension in Bristol, you will find quotes vary wildly and online figures rarely match reality. This guide sets out realistic local price ranges, explains what pushes costs up or down, and shows you how to budget without nasty surprises.
For a straightforward single storey extension in Bristol, most homeowners should budget somewhere between £2,200 and £3,000 per square metre for the build itself, at a standard finish. That means a modest 4m x 5m rear extension of around 20 square metres typically lands between £45,000 and £60,000 before VAT, fittings and professional fees. Bristol sits above the national average because local labour demand is high and access on terraced streets in areas like Bedminster, Easton and Bishopston often adds time to a job.
A double storey extension usually works out better value per square metre, often £1,800 to £2,500, because the foundations and roof are shared across two floors. A two storey side or rear addition of 40 square metres might come in between £75,000 and £110,000 depending on finish. These are honest working ranges rather than promises, and every property is different, but if a quote sits far below them it is worth asking what has been left out.
Two extensions of identical size can differ by £30,000 or more, and the gap almost always comes down to a handful of decisions. Groundworks are the biggest unknown: Bristol's mix of clay soils, old mine workings in parts of south Bristol and Victorian drainage can all mean deeper foundations or drain diversions that only reveal themselves once digging starts. Sensible builders allow a contingency for this rather than pretending it cannot happen.
Above ground, glazing and kitchens dominate. A set of aluminium sliding or bifold doors can add £5,000 to £15,000 on its own, and an open plan kitchen extension carries the cost of the kitchen, structural steels to open up the back wall, and often relocated plumbing and electrics. Finish level matters too: underfloor heating, a vaulted ceiling with rooflights or polished concrete floors are all lovely, and all add real money.
The build price is only part of the picture. You will usually need architectural drawings and structural calculations, typically £2,000 to £5,000 in total, plus planning or lawful development application fees, building control charges and often a party wall agreement if you share a wall with a neighbour, which is common across Bristol's terraced and semi detached streets. Living in a conservation area such as parts of Clifton, Montpelier or Redland can add design constraints and occasionally cost.
On top of that, allow for VAT at 20 percent on most building work, and keep a contingency of around 10 to 15 percent of the build cost for the genuinely unforeseeable. If the ranges above stretch your budget, it is far better to reduce the size or simplify the design at the drawing stage than to cut corners on structure or waterproofing during the build.
Vague quotes cause most extension disputes. Before approaching builders, get drawings and a written specification so every firm is pricing the same job, then ask each quote to be broken down into stages with provisional sums clearly marked. A single headline figure with no detail tells you very little, and the cheapest number on paper is often the most expensive by completion.
Ask any builder for addresses of recent extensions in the Bristol area, confirm they carry public liability insurance, and agree a staged payment schedule tied to completed work rather than dates. A reputable local firm will talk you through where your money goes and will not mind being asked. If you would like a realistic figure for your own property, an informal site visit and honest conversation costs nothing and will tell you more than any online calculator.
A compact single storey extension of around 15 to 20 square metres typically costs £35,000 to £60,000 for the build at a standard finish, before VAT, fees and fittings. Ground conditions, glazing and kitchen work are the main reasons quotes vary.
Many rear and side extensions fall under permitted development, so full planning permission is not always needed, though a lawful development certificate is worth having. Homes in conservation areas, flats and larger designs usually do need permission, so check with Bristol City Council or your designer early.
A typical single storey extension takes around 10 to 14 weeks on site, while a double storey project often runs 4 to 6 months. Add a few months beforehand for design, approvals and pricing, so a realistic start to finish timeline is usually 6 to 12 months.
Tell us about the job and we will get straight back to you with a free quote. DGL work across Bristol and the surrounding area.
Bristol-based, working across Bristol and the surrounding area.