Oak frame extensions are a popular choice across Somerset, from Ham stone villages near Yeovil to farmhouses on the Levels, because they age well and sit comfortably alongside traditional buildings. Costs vary more than people expect, though, so this guide sets out realistic price ranges and the local factors that push a quote up or down.
The oak frame itself is only part of the bill. You're paying for the green oak (or occasionally air-dried oak) used in the posts, beams and trusses, the joinery to cut and peg the frame, and then the foundations, roof, glazing, insulation and internal finish that turn the frame into a usable room.
A simple single-storey box frame with a modest roof pitch costs considerably less than a design with vaulted ceilings, exposed trusses, large glazed gable ends or a jettied first floor. Oak-framed garden rooms and orangery-style extensions, which are common requests in Somerset, also tend to carry a premium because of the amount of glazing and the precision joinery involved.
As a rough guide, a good-quality oak frame extension in Somerset typically costs between £2,200 and £3,800 per square metre, all in, once foundations, roofing, glazing and a reasonable internal finish are included. A straightforward single-storey extension of 20 to 30 square metres therefore often lands somewhere between £50,000 and £100,000, while larger or more elaborate two-storey oak frame projects can run well beyond that.
These figures assume a fairly typical site. Properties in rural parts of Somerset, where access for timber delivery and cranage is tighter, or where existing drainage and services need extending some distance, should budget towards the higher end.
Somerset's geography and planning landscape both influence cost. In parts of the Quantock Hills, Mendip Hills and Blackdown Hills National Landscapes, and in the many conservation areas and listed buildings around towns like Castle Cary, Wells and Bruton, your design will need to respect the existing roofline, materials and setting, which can mean more time at drawing stage and sometimes additional planning or listed building consent costs.
Ground conditions matter too. On the Somerset Levels and in other low-lying areas prone to groundwater or flood risk, foundations often need to go deeper or be designed differently, and floor levels may need raising, both of which add to the groundworks bill. Heavier clay soils found in parts of South Somerset can also mean deeper or reinforced foundations compared with a straightforward sandy or gravelly plot.
Somerset Council, which now handles planning applications across the old district areas, will also expect matching roof coverings (often clay pantile, natural stone tile or thatch in sensitive villages) where an extension is visible from the street, and this can affect material costs.
The biggest savings usually come from decisions made before the frame is ordered, not during the build. A simpler frame with fewer bays and a straightforward roof pitch, standard oak sections rather than oversized feature beams, and sensible, not excessive, areas of glazing all keep the price down without making the extension feel budget.
It's also worth getting quotes from at least two or three timber frame specialists who have built in Somerset before, since they'll already understand local ground conditions and planning expectations, and asking for a clear breakdown between frame, foundations, roofing, glazing and fit-out so you can see exactly where your money is going and where there's room to adjust.
Design and planning typically take 2 to 4 months, with the frame itself often erected within a week or two once on site. Including groundworks, roofing, glazing and fit-out, most Somerset oak frame extensions take 4 to 8 months from first dig to completion.
Many extensions can be built under permitted development rights, but this is more limited in National Landscapes like the Mendip or Quantock Hills, in conservation areas, and on listed buildings, which are common across Somerset. It's worth checking with Somerset Council or a local architect before committing to a design.
Generally yes, an oak frame extension costs around 10 to 30 percent more than an equivalent brick and blockwork extension, mainly due to the material and skilled joinery involved. Many homeowners feel this is offset by the character, strength and longevity of a well-built oak frame.