Cost guide
Oak frame extension cost: where the money goes
An oak framed extension prices differently from a blockwork one, because the frame is both the structure and the finished feature. There is no honest per metre figure, but there is a short list of things that decide the number, and understanding them tells you far more than any average.
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Why oak prices differently
In a masonry extension the structure is hidden and the finishes are applied over it. In an oak framed extension the structure is the finish: the green oak frame is cut and jointed to order, left exposed inside, and expected to be looked at for decades. That means the frame itself is a craft item, priced on the volume of oak, the complexity of the joints and the number of curved braces and feature trusses, not on floor area.
The second difference is glazing. Oak frames are usually paired with large areas of glass, and structural glazing set into or against the frame is a specialist product with a specialist price. Two extensions of the same size can differ enormously once one has a fully glazed gable and the other has conventional windows.
The cost bands inside an oak frame extension quote
Relative weight, not a price list. Use it to see where your own choices move the total.
| Band | What sits in it | How variable |
|---|---|---|
| Groundworks | Foundations, slab, drainage, floor build up | Variable with ground and access |
| The oak frame | Green oak, jointing, raising, pegs and braces | Variable with size and complexity |
| Glazing and joinery | Structural glazing, windows, doors | The most variable band |
| Roof covering | Structure over the frame, tile or slate, insulation | Moderate |
| Fit out | Plaster, electrics, heating, decoration, flooring | Moderate and easiest to phase |
The junction with the existing house, weathering and leadwork, sits across several bands and rewards careful detailing.
What a written quote should name
If a quote does not name these items, you are not comparing like with like.
- The frame specification: green oak volume, joint types, braces and any feature trusses
- Glazing by system and manufacturer, not a single allowance line
- Roof covering and insulation build up, matched to the house where required
- Groundworks with the foundation assumption stated, and what happens if it changes
- Structural engineering and building control through to the completion certificate
- Scaffolding, waste removal and making good where the new work meets the old
Where budgets move
Glazing specification is the biggest swing. Slim framed structural glass, conventional window units set in oak, or a mix of the two are three different budgets for the same opening.
Access matters more than people expect. A frame is raised in large sections, so a tight side passage or no crane position changes the labour involved.
The junction with the existing house decides how settled the finished extension looks. Matching floor levels, weathering the abutment and tying the roof in properly are detail costs that cheap quotes often leave out.
Free site visit, then a written price
We measure, talk through the design and issue a written quote with each band named individually. The frame is made by our own joiners and raised by the same team that builds the rest of the extension, so there is no gap between frame supplier and builder.
FAQs
Common questions
Is an oak frame extension more expensive than blockwork?
The frame and glazing usually cost more than a plain masonry shell, but the comparison depends on specification. An oak frame with standard windows is a different proposition from one with a fully glazed gable, and the written quote makes that visible.
Does green oak need to dry out before building?
No. Frames are cut from green oak and raised fresh. The timber seasons in place over the first years, the pegged joints tighten as it dries, and surface shakes are a normal part of the process rather than a defect.
Does an oak framed extension need planning permission?
The same rules apply as to any extension. Many single storey rear extensions are permitted development within size limits, but conservation areas, listed buildings and estates with removed rights need an application. We confirm the route at the site visit.
Can an oak frame be attached to any house?
Almost any, but the detailing changes. Against a period brick or stone house the frame is usually set slightly apart with a glazed or weathered junction; against a rendered house it can read as part of the original. The design has to respect the host building.
How long does an oak frame extension take?
The frame is made in the workshop while groundworks happen on site, then raised in days. Overall programmes are similar to a masonry extension, with more of the time spent off site.
Ready to price your oak frame extension cost: where the money goes in Kent?
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