Single Storey

Two storey

If you want to build yourself single-storey extensions of 5m x 5m, this will cost you, on average, just shy of  £30,000.

The biggest advantage that timber frame extensions have to impart is that they are relatively quick to build, so they are very common in new build homes. 

Additionally, the fact that they can be manufactured in a factory environment rather than constructed on-site means a greater degree of quality control, speeding up the process without compromising on your materials.

For a two-story timber frame extension, a good rule of thumb when working out costs is to add another 50% onto the previous £30,000 price tag for a single-storey extension measuring 5m x 5m, so long as the upper storey is the same size. 

Therefore, for this example, a two-storey extension of this size will cost you roughly £45,000.

If you hadn't already, now would also be a good point to hire a professional designer, architect or structural engineer to create the technical drawings for your project, showing how your extension will fit with the existing building. 

This will give you a better idea of how your finished extension will eventually look, allowing you to change whatever you don't like. 

Once your chosen architect or designer has finalised your plans, you must attain the appropriate building consent from your local planning authority or council, demonstrating how your plans adhere to standard building and fire protection regulations.

Suppose your proposed extension exceeds the guidelines set out by your local planning office or authority. In that case, you will need to apply for subsequent planning permission before you begin any building work. 

For those unsure of how this process works, you can talk with your chosen contractor, firm or architect, as they will have a deal of experience in this side of projects. 

While doing this, it will also be beneficial to discuss your new timber frame extension materials and which would be best suited to your plans. 

These foundations, or "footings", are usually made from stone or concrete, supporting your timber-framed extensions. Depending on the contractor or firm you have chosen, they may construct your timber frame extension on-site or in a workshop. 

To your construction timber framework, they will add structural timber frame panels, either softwood or hardwood and insulation, whether a sheet panel system or otherwise, for energy efficiency. 

This method helps to keep the timber frame construction project running efficiently.

Size of Extension

Timber Types

Again, the size of your timber frame extension is measured in the mean floor area and the number of storeys you choose to construct. The £1,400 to  £2,400 price tag mentioned above covers softwood timber frame extensions at the lower end, with hardwood at the other.

These prices also include the materials, planning, construction and installation services. The additional 50% per floor also applies. 

It is only a 50% increase for a second storey because you should have already factored in the price of a roof for the initial one storey extension.

If you decide on more than two storeys for your timber frame extension, you will need to factor in additional costs, such as heavy-duty structural timber frames for your ground floor to support the extra weight.

While the most common type of timber used in timber frame extensions is softwood. 

Depending on your plans, your designer, contractor, or architect may suggest choosing timbers besides those that are better suited to your designs. 

The cost of these other timbers, alongside overall costs, include:

• Maple - £1,600 to £2,100 per m2.
• White Oak - £1,900 to £2,300 per m2.
  
• Red Oak - £2,000 to £2,500 per m2.

While the price of materials for your timber frame extension will be the same wherever you live, the price of skilled labour can vary dramatically between different locations. 

For example, the cheapest labour costs anywhere in the UK can be found in Northern Ireland and the North of England. 

After this comes the Midlands and South Wales. The next highest areas regarding labour costs are Southwest England, East Anglia and Scotland.  

The second-highest labour costs in the UK are found in the Southeast, in areas such as Kent and outer London. 

Finally, around 20% higher than anywhere else in the UK, the most expensive labour costs are found in inner London.

There is also a range of timber frame methods of construction you will have to choose between:

Platform Frame

Vertical Pane

The platform frame method is ideal for those building multi-storey extensions, as it can support up to seven storeys - if you want to build that high. 

Each timber frame panel is made into load-bearing supports for the upper storey, allowing your designers to use shorter lengths of timber for the prefabricated panels. 

Your contractors will also have supported platforms and floor structures to work from.

This is possibly the most common method of timber frame extension construction. 

A traditionally built extension like this uses timber lengths placed vertically to create structural supports for your panels and any substructures you want to create. 

This is one of the quickest ways to build your timber frame extension and doesn't require overly skilled contractors to carry out the job.

Most of the prices timber frame extension firms quote, you will cover most costs, including the flooring, the ceiling and roof trusses and timbers required. 

However, most will neglect to include costs for many elements of your extension, including your structural insulated panels, foundations, concreting, roof covering, internal joinery, fire-resistant linings and outer wall covering or external cladding. 

Each of these can add considerable sums to your overall costs. The outer wall skins possibly being the most expensive of your timber frame extension costs, depending on your chosen materials.