Oak Frame Extensions
MTD Building Contractors specialise in oak frame extensions that blend traditional craftsmanship with modern building standards. Our oak frames are handcrafted using green oak and traditional joinery techniques, creating stunning architectural features that add character and value to any property.
What Is an Oak Frame Extension?
An oak frame extension uses a structural skeleton of green oak beams and posts, jointed with traditional mortise and tenon joints and secured with hardwood pegs. The frame is infilled with insulated panels — typically SIPs or timber frame — and clad externally with brick, stone, render or timber boarding. The exposed oak frame is visible from inside, creating the warm, characterful aesthetic that makes this construction method so desirable. Oak frame extensions are used to add orangeries, garden rooms, dining rooms, kitchens and entrance porches to existing properties. They work particularly well on period properties, barn conversions and rural homes, but can also complement modern houses.
Oak Frame Extension Costs
An oak frame extension typically costs between £2,500 and £4,000 per square metre — approximately 30–50% more than a standard masonry extension of equivalent size. A 20 sqm oak frame orangery would typically cost £50,000 to £80,000 including foundations, frame, infill panels, glazing, roofing, electrics and internal finishes. The oak frame itself usually accounts for around 25–35% of the total build cost, with the remainder covering foundations, infill, roofing, glazing, mechanical and electrical services, and finishes. The cost of the frame depends on the complexity of the design, the number of trusses and bays, and the size of the timbers. Green oak is sourced from sustainably managed UK and European forests.
Planning Permission for Oak Frame Extensions
Oak frame extensions are subject to the same planning rules as any other extension. Many fall under permitted development rights, but properties in conservation areas, listed buildings, and extensions that exceed permitted development limits will require full planning permission. In practice, oak frame extensions on listed or heritage properties are often looked upon favourably by planning officers because the construction method is sympathetic to the character of the building. Design and access statements submitted with planning applications for oak frame work can demonstrate how the extension complements the host property. MTD Building Contractors prepare all planning documentation and liaise with the local planning authority on your behalf.
Green Oak and the Seasoning Process
Oak frames are constructed from green (unseasoned) oak, which is easier to work and joint than dried timber. Over 12–24 months the oak gradually seasons in situ, developing characteristic splits (known as shakes) and a silver-grey patina. These shakes are entirely normal and do not affect structural integrity — they are part of the material's appeal. The frame is designed to accommodate natural shrinkage during seasoning. We advise clients on what to expect so there are no surprises.
How Long Does an Oak Frame Extension Take?
The oak frame is typically manufactured off-site over 4–8 weeks by specialist oak frame carpenters. During this time, foundations and groundworks are completed on site. The frame is then delivered and raised (erected) in 2–5 days — an impressive process to watch. The infill panels, roofing, glazing and internal fit-out take a further 6–10 weeks. The total build time from start of groundworks to handover is typically 12–20 weeks. Including the design, planning and frame manufacturing period, the overall project timeline is usually 6–12 months from first enquiry to completion.
What's Involved
Every oak frame extensions project is managed from initial consultation through to final handover. Here's what we deliver:
Frequently Asked Questions
How much does an oak frame extension cost?
An oak frame extension typically costs between £2,500 and £4,000 per square metre, making them more expensive than standard construction but offering unique character and long-term value.
How long does an oak frame extension take?
The oak frame itself is typically manufactured over 4-8 weeks, with the full build taking 12-20 weeks depending on size and complexity.
Will an oak frame extension match my existing property?
Yes. Oak frames are particularly well-suited to period properties, barn conversions and rural settings, but they can also complement modern homes as a design feature.