If you want to build a standard budget extension, then you should look at structures made from Douglas Fir and other softwood species. However, choose premium hardwood such as oak to impress your friends and neighbours with an extension that’ll last.
An average oak frame extension costs in the UK from £2,000-£2,700/m2 plus crane hire, although you can build one for slightly less. Moreover, a typical duration for the build stretches from 4 to 12 weeks, depending on size and level of complexity.
So, apart from the snob value, why would someone want an oak framed extension? We’ll go into this in more detail later. But for now, let’s say that they are stunning, need hardly any maintenance, and are impervious to all the problems that softwoods suffer from.
Although many magazine articles and online home design blogs mention oak extensions as a design project, they say very little about building modern oak framed house extensions. This is because each extension kit is unique to individual circumstances. For this reason, we can only give an approximate ballpark figure for a build. If you want an accurate quotation, contact an oak frame specialist company, and use a local general builder to lay the foundations based on the extension’s construction drawings. Probably the best way to find suitable companies is to complete the form on this page.
Many factors influence the price you pay. We’ll explore this information in the following sections.
How Much is an Oak Framed Extension?*
The following table shows some typical oak framed extension prices per square metre. You should use this as a cost calculator to decide which type is best for you.
|Extension Size||Type of Timber||Cost per m2||Total Cost|
|15 m2 Single Storey||Small||White Oak||£1,900-£2,300||£28,500-£34,500|
|30 m2 Single Storey||Medium||£57,000-£69,000|
|30 m2 Double Storey |
(2 x 15 m2 Storeys)
|Small, double storey||£42,750-£51,750|
|60 m2 Single Storey||Large||£114,000-£138,000|
|15 m2 Single Storey||Small||Red Oak||£2,000-£2,500||£30,000-£37,500|
|30 m2 Single Storey||Medium||£60,000-£75,000|
|30 m2 Double Storey |
(2 x 15 m2 Storeys)
|Small, double storey||£45,000-£56,250|
|60 m2 Single Storey||Large||£120,000-£150,000|
*Note: These prices are estimates based on costs per square metre, researched at the time of writing (June 2021). Only use them as a guide during your own research.
Oak Frame Extension Price Factors
Many factors affect the price of oak framed extensions. Here are a few of the most important.
Size of Extension
Even though it’s probably obvious, we should say that a large oak framed extension costs more than a small one. However, it doesn’t end there; A single-storey extension costs less than one with multiple storeys. Moreover, as a general rule of thumb, the cost of a ground floor and first floor together cost around 1.5 times the cost of a single storey. Finally, if the oak framed extension is heavy, you’ll need more oak timber pieces of a larger cross-section to support the additional weight.
To express this in numbers, we could say the following.
An average 15m2 single-storey extension (such as an oak framed kitchen extension) made from white oak will set you back between £28,000 and £35,000, whereas a large white oak extension of around 60m2 (such as a lounge/diner) costs between £114,000 and £138,000.
There are two types of oak commonly used in oak framed extension kits; White oak and red oak.
Generally, the cost of the two types fluctuates, with white oak sometimes slightly less expensive than red oak, and at other times it’s more expensive depending on the market. Other differences include:
- Colour – Red oak has a pinkish tint, while white oak has a brownish yellow colour. The names “red” and “white” refer to the colour of the finished timber, not the colour of the original tree.
- Hardness – White oak is slightly harder than red oak.
- Grain – Red oak has a more pronounced grain than white oak. White oak also looks somewhat smoother than red oak.
- Water and rot resistance – White oak has more resistance to water and rot than red oak, mainly because of its closed, dense grain.
Oak timber frame kits are heavier than softwood, so they need more robust and larger vehicles to transport them from the factory to the construction site. You will also find that the transportation costs increase depending on the distance between factory and site, especially if you live in a remote location when the only access are minor roads.
Typically, a qualified architect will design the oak framed extension. Their fees are usually based on a percentage of the total job cost, typically around 10%, with a minimum level agreed upon before you sign the contract.
The design of the structure also affects the overall cost. For example, simple barn style frames usually cost less than complex designs involving large room spans or complex roof styles.
You will also find that a high-quality specification and finish will significantly affect the overall cost.
Remember that you’ll probably require a different contractor to add foundations and brick or stone cladding.
When dealing with oak frames, it’s essential to use a crane to unload from the transport and when assembling the framework. The cost to hire the crane and driver will depend on the boom length, lifting capacity and rental duration.
Labour Cost & Estimated Timeline Examples
As with any construction work, building an oak framed extension requires various tradespeople to carry out the different tasks necessary for your extension. However, if you have building skills and a team of helpers, many specialist oak frame manufacturers offer a self-build option and provide the oak pieces with assembly instructions.
|Tradesmen Type||Typical Average Daily Rate (incl VAT)|
|Architect||Around 10% of total job cost|
Typically, the manufacture of the oak frames takes place in a factory or workshop. Moreover, from placing the order to delivery can take up to 8-10 weeks, depending on the complexity of the design.
Likewise, the time taken to erect the frame depends on the complexity and size of the extension. Usually, however, you can expect to erect a standard frame in anything from 2 to 10 days. But don’t forget that this is to produce a skeleton framework. Once it’s assembled, you need to turn it into a habitable structure, which will take longer.
Typically, using qualified tradespeople, it takes around 6-8weeks to finish a small extension (15m2), 10-12 weeks for a medium-sized extension (30m2) or 12-14 weeks for a large extension (60m2). Remember that all durations are approximate, as many unforeseen problems can cause delays with the expected finishing date.
Building an Oak Framed Extension Overview
Every oak framed extension is unique to its location and position relative to the house. Furthermore, its size, use, and appearance depend on your preferences and what the local authority will allow.
Therefore, we cannot give exact instructions on how to assemble and finish an oak framed extension. Instead, we’ll give general guidelines, leaving the detail to the contractors on site.
- Contact the oak frame manufacturer and explain what type of extension you prefer. Ask for a quotation to supply the frame and a general plan for the architect to use.
- Contact your architect with the information supplied by the manufacturer. Together, they will produce construction drawings suitable for submission to the local authority. You might not need planning permission; your architect will know whether this is a requirement. However, you must comply with the Building Regulations, and the Building Control office must have a copy of the construction drawings with material specifications to monitor the build.
- Find a contractor to handle the foundations and concrete floor. You will also require tradespeople to finish the build.
- Start foundations and construct up to DPC (damp proof course). Then pour the concrete floor.
- Accept delivery of the oak frame timbers and crane into place. Assemble the timber into the framework according to the manufacturer’s instructions.
- Infill the framework walls with insulation board and add the outer skin using timber or brickwork. Note: the extension must comply with the regulations on insulation and damp proofing.
- Install doors and windows.
- Cover the roof with the agreed type of roof covering.
- The extension is now watertight and insulated. So, finish the inside depending on the extension’s use. Then, at the appropriate time, open the extension to the remainder of the house.
Oak Frame Extension Ideas
You can build almost any structure using an oak frame. And it will perform just as well as any other building method. However, the main difference is that the building or extension will have a touch of class and sophistication about it that will match a period home, idyllic countryside second home, or even your main home.
Let’s mention a few ideas you can try with an oak framed extension. And remember that with most of them, you will probably need to apply for planning permission.
- Garage – This can be a single, double or triple garage. If needed, you can add a garden shed or outhouse to the design. And what’s more, you can make it appear to be a converted barn or stable.
- If you have room, you might try a garage with a living area above.
- You can make an oak framed glass extension into a distinctive conservatory or orangery. The large spaces between upright pillars work well with large double glazed picture windows. You might also choose a roof to match your home, solid or with an integral lantern.
- Porches are another excellent way to use oak frames. They can be as small or as large as you prefer and perfectly complement the house’s front.
- An oak framed extension can be a kitchen, lounge, dining room, bedroom, or indoor pool house. Any of these look good if built onto a house that matches the style.
Benefits of Oak Framed Extension
If you intend to spend the extra money on an oak framed extension, you must have some advantages when using the material.
Because of its hard closed grain, oak doesn’t allow water to penetrate easily. Therefore, it’s resistant to weather effects, wet rot and all kinds of fungal attack. Moreover, oak is also high in tannins which deter wood-boring insects and, together with its hardness, makes it very difficult for wood boring insects to gain a hold. However, you might see small holes caused by woodworm beetle and other insects. Don’t panic; the holes are only a few millimetres deep. Below this, the wood is too dense for further boring.
Because of oak’s resistance to just about any natural attack, it is virtually maintenance-free. All it needs is a coat of stain to keep it looking beautiful. Furthermore, over time the wood weathers naturally and dries out further. This action increases its inherent beauty, increases its structural strength, and its ability to withstand insects and fungi even more.
At present, most UK oak frame manufacturers use sustainably farmed plantations to supply the timber used in their products. In their managed woodlands, for every tree felled, at least two saplings take its place.
Planning Permission & Building Regulations
You might need to apply for planning permission for your oak framed extension depending on the following :
- Where do you live in the country, and what are the local authority’s area plans?
- What is the size of the extension; its floor area, height and total volume?
- Does the design complement your existing home and those of your neighbours?
- How far is the extension is from the boundary of your land? And does it alter the front elevation building line?
Usually, you or your architect must contact the local authority before the planning stage for further information.
Submitting planning permission isn’t free of charge. A typical planning application costs about £460 for a complete home, while extensions cost around £200. Your local authority publishes the fees on their website, so you should check to confirm the exact amounts.
But, even if you don’t need planning permission, your extension must comply with Building Regulations.
The relevant regulations cover aspects of your extension related to structural integrity, fire safety, energy efficiency, dampness and drainage, ventilation, plumbing, electricity, quality of materials, and craftsmanship.
Wooden Extension Fire Protection
Oak framed extensions contain a large amount of wood. Although seasoned oak chars when exposed to flame, it’s usually only a couple of centimetres on the surface that suffer. Nevertheless, specific regulations cover the use of wood in buildings and their exposure to fire.
The regulations dealing with fire protection reduce the risk of fire on your property and the effect the fire has on the building materials. Furthermore, if a fire manages to ignite, the regulations ensure there are adequate fire evacuation procedures and exits in place.
Your architect knows the appropriate building regulations, and the oak frame manufacturers should know how they affect their product. Therefore, it’s up to you to confirm that suitable protection and prevention measures are in place at the design stage.
Oak Frame Extension FAQ
How much does an oak framed conservatory cost?
The exact price depends on the size, specifications, and detailing of the conservatory. Realistically, the cost for a good quality conservatory of around 15-30m2 floor area would be about £2,300-£2,500/m2, plus VAT.
What is a green oak extension?
Green oak is oak that was felled in the last 18 months or so. Therefore, it still has a reasonably high water content as it hasn’t fully seasoned. A green oak frame extension is as strong and durable as air-dried seasoned oak. But, it’s much easier to work and is less expensive than fully seasoned. Once in your home, the oak timbers will continue to season in place. Furthermore, the subsequent shrinkage draws the structure’s joints even tighter together and brings the joints more into alignment. Finally, the ageing process increases the frame’s strength and gives the oak a much better appearance.
Is oak frame expensive?
Oak frames are a premium building material but aren’t that much more expensive than standard timber. For a complete job, from foundations to finishing, you can typically spend around £2,500/m2. However, remember that this amount is approximate, as many factors will change the overall price.
Is oak a good building material?
Oak is probably one of the best building materials we use. Overall, it is the most robust and durable timber in use in the UK, and its composition makes it resistant to fungal and insect attack. Although its close grain prevents water from soaking into the grain, it will eventually rot if left standing in water. Having said that, when kept dry, oak frames can last for 500 years or more.
What are the disadvantages of oak wood?
Although oak is probably the best timber to use in the construction industry in the UK, it has its drawbacks:
- Oak is heavy. Whereas a couple of carpenters could easily carry and install lengths of Douglas Fir softwood, you need a crane to offload oak frames from a lorry and lift them into place.
- It’s much more expensive than softwood. So, we generally use it in places where oak’s beauty shows.
- It’s highly durable and resistant to fungal and insect attacks. And if kept dry, it will last for over 500 years.
- Oak doesn’t need much maintenance and is very easy to repair.
- Oak is more resistant to fire than softwood, and if exposed to it, flames will only cause the surface to char.
If you want to build an extension and have the money to spare, you can’t go far wrong using oak frames, especially if you live in a period home.
Although oak frames are more expensive than softwood timber framing, they are more durable, resistant to many forms of attack, and will last for many years. But, you need professional help to plan and build your extension.
Complete the form on this page, and you’ll receive up to three competitive quotes specifying the cost of an oak framed extension to complement your home and probably be well within your budget.