Ask five builders what an extension costs and you may get five different answers, largely because "extension" covers everything from a modest 3m rear infill to a two storey side return with a new kitchen and steel beams. Below are the ranges we see across Worcester and the surrounding villages, what pushes a price up or down, and the costs homeowners routinely forget to budget for.
Most Worcester extensions land somewhere between £2,000 and £3,000 per square metre for the building work itself, finished to a decent standard but before you start choosing expensive kitchens or bathroom suites. That covers foundations, brick and block or timber frame walls, roof, windows and doors, plastering, first and second fix electrics and plumbing, and decoration.
As a rough guide: a 20 square metre single storey rear extension usually sits in the £45,000 to £65,000 bracket, while a two storey side extension of similar footprint per floor often comes out at £85,000 to £130,000. Two storey work is generally better value per square metre because you are getting twice the floor area from one set of foundations and one roof.
Garage conversions and loft conversions sit lower, often £1,200 to £1,900 per square metre, because the structure largely exists already. A single storey extension with a lot of glazing, a flat roof with lanterns and a large steel opening into the existing house will push towards the top of the range or beyond.
Ground conditions matter a great deal locally. Parts of Worcester sit on clay, and where there are mature trees nearby, Building Control will often want deeper foundations or a reinforced raft. Going from a standard 1m trench fill to 2.5m can add £4,000 to £9,000 on its own, and it is rarely known for certain until the trenches are open.
Flood zone status is worth checking early if you are near the Severn or Teme, in areas such as Diglis, Hylton Road or parts of St John's. It does not necessarily stop the work, but it can change floor construction and how the Environment Agency and planners respond.
Access is the other big one. Victorian terraces around Barbourne and Rainbow Hill often mean no side access, so every skip load and every pallet of blocks goes through the house, which adds labour days. Detached properties in villages like Kempsey, Hallow or Powick usually give easy access and a cheaper build.
Conservation areas and listed buildings in the city centre and around the Cathedral bring stricter material requirements, such as matching handmade bricks or timber windows rather than uPVC, which can add 10 to 20 percent to the external envelope cost.
The build price is not the project price. Budget for professional and statutory fees on top, and allow a genuine contingency of 10 to 15 percent. On a £60,000 extension that is £6,000 to £9,000 set aside, and on older properties it often gets used.
A party wall award is commonly needed for terraced and semi detached homes, and structural calculations are needed for almost any opening into the existing house.
The cheapest quote is often the least detailed one. Before you compare figures, check each price covers the same specification: window type and manufacturer, level of insulation, whether plastering and decoration are included, who supplies and fits the kitchen, and whether muck away and skips are priced in. Vague single page quotes usually mean variations later.
Ask how the price handles unknowns. A good builder will tell you honestly that foundation depth and any drainage diversion are provisional until the ground is open, and will give you a rate for extra depth up front rather than a surprise invoice. Also ask for a realistic programme; a typical single storey extension runs 10 to 16 weeks on site, and anyone promising six weeks is either very optimistic or not planning to finish properly.
Many single storey rear extensions fall under permitted development, which allows up to 4m projection on a detached house and 3m on a semi or terrace, subject to height and material conditions. Conservation areas, listed buildings and previously extended properties are common exceptions, so it is worth a quick check with Worcester City Council before you design anything.
It often does in Worcester, particularly where it adds a proper bedroom or turns a cramped kitchen into a usable family space, but it is not guaranteed. Every street has a ceiling price, so if you are already near the top of what similar houses sell for locally, treat the spend as buying the space you want rather than an investment.
Avoid large upfront deposits. A reasonable arrangement is a small payment for materials at the start, then staged payments tied to completed milestones such as foundations, roof on, plastering and completion, with a final balance once you are satisfied with the snagging.
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