Timber frame extensions are being used more and more. This is due to how quickly they can be built, their energy efficiency and the wide array of designs possible.
If you’re considering a timber frame extension or building, you may be wondering how much you should expect to pay.
This article will cover the costs involved, the sorts of factors that can alter these prices and common questions people have surrounding the use of timber frame for an extension.
Cost per m²
A structural timber frame can be priced at £150/m² of the gross internal floor area.
Included within this timber frame cost is vertical studs with plywood sheathing to form internal and external walls, horizontal joists and sheathing to form upper floors and roofing and roof trusses.
This rate is for the south-east or southern London area. Price adjustments based on location are detailed within the factors section.
Extension Cost per m²
Below are the average costings of all the elements needed to create a timber frame extension:
| Element | Work Included in Element | Cost |
|---|---|---|
| Substructures | Strip Foundations, Blockwork / Engineered Brick Cavity Walls, DPC, Concrete Slab, hardcore, blinding, DPM, insulation, screed | £122/m² |
| Frame | Timber Frame Structure - including stud walls, roof trusses, upper floor structure | £165/m² |
| Roof | Roof coverings including battens, membranes, insulation, felt, tiles, soffit, fascia & rainwater goods | £136/m² |
| Stairs | If required | £23/m² |
| External Walls | SIPS (studs in frame) - including insulation, OSB board, membranes, plasterboard. Chimneys | £132/m² |
| Windows and External Doors | uPVC windows / doors | £125/m² |
| Internal Walls & Partitions | Plasterboard and insulation (studs in frame) | £65/m² |
| Internal Doors | Softwood internal doorsets, ironmongery and decoration | £73/m² |
| Wall Finishes | Paint, wall tiling, skim etc | £40/m² |
| Floor Finishes | Carpet, tiling, hardwood flooring, skirtings etc | £50/m² |
| Ceiling Finishes | Plasterboard and skim | £31/m² |
| Furniture, Fixtures, and Equipment | Stove, Kitchens, Bathrooms, Wardrobes, shelving etc | £125/m² |
| Mechanical | Heating & Plumbing | £83/m² |
| Electrical | Electrics & Lighting | £90/m² |
| External Works | Storm & foul drainage, water & sewage connections | £60/m² |
| Sub- Total | £1320/m² | |
| Design Team & Survey Fees | £135/m² | |
| Prelims | Scaffolding, welfare, warranties and site attendances | £135/m² |
| Total | £1,590/m² |
Therefore, for an average single-storey timber frame extension of 4m x 5m, £28,880 would be a good price to budget for.
Why You Can Trust this Data
We worked directly with a Quantity Surveyor of 7+ years involved in £600M capital expenditure works for a large hotel chain to develop these costs back in 2020. If you see similar cost values and breakdowns on other websites, then you can probably assume they have taken them from this article and Quantity Surveyor.
Factors Affecting the Cost
Number of Storeys
When timber frames are used for structures higher than two storeys this can often increase cost per m². This is because of more structural timber required at lower levels to support the structure.
Specification of the System Selected
This includes elements like the size of timbers, type of plywood and the thickness of plywood. All vary in price and can cause cost differences.
Weight of the Structure
If heavy loads need to be supported heavy loads, more timber is needed to adequately support the structure, thus increasing cost.
Level of Design Required Prior to Construction
In particularly complex timber frame structures more time can be spent by a designer / structural engineer on drawings and design, thus increasing the system cost.
Location
The above rates are for the South East/Outer London Area. You can use the following adjustments depending on where you live. These are based on the BCIS and Spon indices.
| Region | % Adjustment |
|---|---|
| South East (Southampton, Oxford, Kent, Outer London) | 0 |
| Inner London | +4% |
| South West (Bristol, Exeter) | -4% |
| West Midlands (Birmingham) | -10% |
| East Midlands (Northampton, Nottingham, Leicester) | -10% |
| East Anglia (Cambridge, Norwich, Ipswich) | -5% |
| North West (Liverpool, Manchester) | -12% |
| Yorkshire and Humberside (Leeds, Sheffield) | -11% |
| North East (Newcastle, Sunderland) | -10% |
| Scotland (Edinburgh, Glasgow) | -6% |
| Wales (Cardiff, Swansea) | -9% |
| Northern Ireland (Belfast) | -12% |
How Does the Material Shortage Affect Prices in 2023?
Prices within the construction industry have continued to rise into 2022. Because certain material costs are fluctuating rapidly, tradespeople pricing up jobs longer than a month away may add extra to mitigate the risk.
Timber frame extension used many materials that are in short supply at the moment. Timber is the obvious one and since the time of updating this section (19/01/2022), the timber shortage has eased since 2021, where prices more than doubled.
However, prices will likely still rise due to border congestion between the UK and Scandinavian ports meaning lower supplies according to CLC.
But the CLC has warned that border congestion both in the UK and at Scandinavian ports may lead to reduced supplies and higher prices this spring.
General construction costs are expected to rise 5% in 2022 due to wage and material cost inflation.
Other materials used within a timber extension construction include:
- Roof tiles
- Bricks and blocks
- Cement
- Concrete
- Electrical components
- Aggregates
- Screws
- Fixing
- Plumbing items
Get Prices on Timber Frame Extensions Near You
Timber extensions are still relatively new in the UK market. This means finding professional builders specialising in timber frames can be difficult.
We work with all the best timber frame extension builders ready to price your job. Get free, no-obligation quotes in your local area and compare prices using the form below.
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About the Author
Alex Johnson is a qualified quantity surveyor and writer with a passion for conducting original research and uncovering the true cost of jobs. His cost data has been referenced by EDF Energy and the Scottish Government.