Single Storey Extension Costs in Peterborough: A Realistic Guide

Typical price ranges for the Peterborough area

Builders usually price extensions per square metre of floor area. Locally, a sensible working figure for the build itself is roughly £1,900 to £2,800 per square metre, with high-specification projects going above £3,000. That covers the structure, roof, windows, plastering, electrics and basic heating, but normally not the kitchen or bathroom fittings, flooring or decorating.

Smaller extensions cost more per square metre than larger ones, because fixed costs such as setting up the site, scaffolding, skips and knocking through the back wall are spread over less floor area. Rates here are noticeably lower than in Cambridge or London, but they are not cheap, and any quote far below these ranges deserves careful questions about what has been left out.

• Small rear extension, around 15 square metres: roughly £35,000 to £50,000
• Medium kitchen and dining extension, around 25 square metres: roughly £50,000 to £75,000
• Large wraparound or open plan extension, 35 to 40 square metres: roughly £75,000 to £110,000 or more
• Most builders add VAT at 20 percent, so always check whether a figure includes it

What pushes the price up or down

Two extensions of identical size can differ by £20,000. The biggest swings come from how the new space joins the old house and what you put in it. A wide opening in the back wall needs a steel beam, structural calculations and temporary propping. A kitchen extension needs plumbing, drainage, extraction and far more electrical work than a simple sitting room.

Ground conditions matter a great deal in this area. Much of Peterborough sits on clay, and the fenland to the east towards Whittlesey, Thorney and Eye has soft, peaty ground. Both can mean deeper trench foundations or, in some cases, piling or a raft, particularly near mature trees. That can add several thousand pounds, and nobody knows for certain until building control has seen the trenches.

• Glazing: wide bifold or sliding doors typically cost £4,000 to £10,000, and roof lanterns £2,000 to £5,000
• Roof type: a flat roof is usually cheaper than a pitched, tiled roof
• Drains: building over or near a shared sewer needs an Anglian Water build over agreement and may mean moving a manhole
• Access: terraced streets in areas like Millfield or Woodston, where everything goes through the house, slow the job down
• Matching materials: buff brick, local stone or slate in villages such as Castor, Ailsworth or Stamford side properties costs more than standard facing brick

The costs that sit outside the builder's quote

Homeowners are often caught out by fees that never appear in the build price. Allow roughly 10 to 15 percent on top for professional and statutory costs. Drawings from an architect or architectural technician usually run from £1,500 to £4,000 depending on detail, and a structural engineer's calculations from £500 to £1,200.

Many rear extensions fall under permitted development, so they do not need a full planning application to Peterborough City Council. Permitted development rights are sometimes removed on newer estates, and they are restricted in conservation areas and on listed buildings, so check before you rely on them. Building regulations approval is always needed, and the fee is typically several hundred pounds to around £1,000. If you are building on or near a boundary, a party wall agreement may add £1,000 or more per neighbour if surveyors are involved.

Then there is the finish. A fitted kitchen can cost anything from £8,000 to £30,000, and flooring, decorating and making good the garden or patio often add another £3,000 to £8,000.

How to get a quote you can trust

A reliable price needs proper drawings. Quotes based on a sketch and a conversation are estimates, and the gaps tend to reappear later as extras. Ask each builder to price from the same drawings and specification, and to itemise the quote so you can see what is and is not included.

Keep a contingency of around 10 percent for things that cannot be known in advance, such as foundations, hidden drains or the condition of the existing wall. Ask how variations are priced, what the payment stages are, and whether the builder will deal with building control inspections. A slightly higher quote that is clear and complete is usually the cheaper one by the end of the job.