There's no questioning the premium look you'll creating when adding an oak frame extension to your home. But with this style of extension comes a raft of decisions and choices that need to be made.
Much the same as when building an oak frame house, a lot of the earlier stages of the process will be fundamental in completing a successful build. From design decisions through to issues such as how to connect an oak frame extension with your house, research and planning is key.
That said, with the right supplier, plan and knowledge of how to add an oak frame extension in place, the end results can be stunning. Here's what you need to know.
Article continues belowWhat type of homes do oak frame extensions suit the most?
One of the main appeals of an oak frame extension lies in its ability to suit almost every type of home. From period properties and bungalow renovations right through to new builds, oak frame extension ideas can be adapted to suit most sizes, shapes and styles of home.
So, whether you're looking to add an oak frame conservatory or an oak frame kitchen extension, the flexibility of the construction method and the different looks available mean there are very few limitations to what can be achieved. The materials and methods of construction also mean that architectural features, such as vaulted ceilings and glazed gable ends can also be created with relative ease.
And, unlike on-site methods of construction such as masonry, the majority of the oak frame structure is prefabricated off-site meaning it can also be quick to build, thus causing the least amount of disruption to your current home once the work begins.
Design considerations for an oak frame extension
The design of your oak frame extension, like other types of house extension will start with you understanding how you want to use your new space. Are you looking for a large open plan kitchen extension, or a cosy snug where you can enjoy garden views, whatever the weather.
Once you understand how you will use the space, one of the most fundamental questions regarding the design of an oak frame extension, is how much oak will you want to leave exposed?
Are you looking to complement a period home with more traditional exposed oak rafters, purlins or trusses, or are you seeking a more streamlined look, in which case you may want to pare back the oak to the structural minimum.
Typically, the most cost-effective route of adding an oak frame extension lies is approaching an oak frame company who can provide an in-house design service, or an architectural practice with experience designing timber frame extensions. Their working knowledge of the possibilities, challenges and limitations of this build system will ensure you get a design that not only meets your needs, but is suitable for the materials you will be using during construction.
George Allen, regional design consultant for Oakwrights says areas that need particular consideration are:
- First floor windows: These often dictate roof design as if you have windows on the adjoining wall, then a flat or mansard roof design may be your only option
- Internal floor space: What access, routes across the extension and furniture positions might influence your design?
- Glazing: If you are thinking about three fully glazed walls for example, then plug sockets will need to go in the floor
- Plinth materials: If you are having a brick or stone plinth make sure it will match or complement your home
- Access to the extension: Where will this be? Can you use an existing external door, or you will need to knock through an external wall?
- Heating: How will you heat your oak frame extension? Underfloor heating continues to be very popular as do log burning stoves
Creating a cohesive visual connection
As with any house extension ideas, the connection, and impact of this on the existing house also requires a great deal of thought during the design phase. Extensions which are subservient, but draw their cue in terms of design and materials from the existing house, can often work well, although there is equal aesthetic value in creating contrast too.
One way of making a new extension feel instantly at home is to introduce elements of oak into the main house at the same time as building an extension.
"You could include elements such as an oak frame porch or an internal glazed oak screen, both of which would help to visually tie the extension to the existing house," suggests architect Mike Hope of Roderick James Architects ; a practice well versed in designing oak frame homes.
George Allen is a regional design consultant for Oakwrights, one of the UK's leading suppliers of oak frame buildings.
Building an oak frame extension
Once your design is agreed and any necessary planning permission approved, what comes next? It's a relatively simple three stage process says George Allen.
- Production of the oak frame off site, while onsite your builder will complete the extension foundations
- Installation of oak frame, roofing, walls and glazing
- Interior finish
Off-site production phase
Most homeowners will work with a specialist oak frame company when adding an oak frame extension. This company may work on the basis of design and supply of frame only, or they may also provide the 'encapsulation' system.
Traditionally, an oak frame would have been infilled with wattle and daub, or brick. Today, the options are more varied, says Paul Edmunds, the founder of Welsh Oak Frame, noting how the changes are necessary to ensure oak frame extensions meet Building Regulations standards for thermal efficiency.
"Softwood stud, SIPs (structural insulated panels) or timber panels are all used to encase the system," says Paul Edmunds. "Then, when it comes to the external finish, the options are wide ranging. Timber cladding, brick work, masonry, render, block or stone can all be used. This allows the external appearance to fit vernacular local styles and satisfy any extension planning permission requirements."
It should however be noted that heavier claddings such as brick and stone often have to be built off their own foundations, which will likely have an impact on the timings and your final budget. As will the amount of architectural glazing you use in your final structure.
In terms of the stages of building an oak frame extension, Paul Edmunds say you can typically expect it to look as follows:
- Foundation by ground workers
- Raising frame to rafter roof level
- Clad roofing or slate tiles
- External envelope brickwork, weather boarding
- Internal first and second fix
Most oak frame companies will require the homeowner to commission a builder or groundworking company to complete the foundations, before delivering and erecting the oak frame on site.
Once the oak frame is constructed, the homeowner will typically have the option to project manage individual trades to finish the extension, or commission a builder to manage this process for them.
Time frame for building an oak frame extension
In general, expect to allow around 5 - 6 months for your oak frame extension schedule, says George Allen. This will ensure there is sufficient time for the design and consultation process, planning, groundworks and then the oak frame assembling and roofing, with the interior work and glazing done last.
In terms of the the time on site, it will all depend on the size and scale of your extension says Paul Edmunds.
Paul Edmunds is the founder of Welsh Oak Frame, one of the leading suppliers of handcrafted oak frames in the UK that was established over three decades ago.
Practical considerations when connecting your oak frame extension to your home
Oak frame extensions are typically built to be structurally independent. In other words, the house and extension sit next to one another but don't rely on the same set of foundations.
"An oak frame extension will generally be structurally separate to your home," confirms George Allen, "and the extension will often connect through a softwood battens, a weatherproof seal and capping on the side, along with a softwood roof rafter with flashing and detailing on the roof join."
"As an extension, it can be butted against the existing structure," says Paul Edmunds, "and there are various ways to anchor it to the existing home by means of stainless-steel resin anchored into the masonry/brickwork. This will be done with all the necessary weather-stripping and damp-proof courses in the appropriate places."
Keeping them structurally separate can be beneficial, particularly with older properties adds Merry Albright, creative director at Border Oak. “It means we don’t need to mess around with the main building or foundations, as often we are extending an old building and you never know what you may find. This route can offer more control over the whole project and the costs involved,” she explains.
Another option is to create a glass link extension between the two buildings, a device which visually separates old from new and helps draw light into the house.
Merry is the creative director at Border Oak. She is involved with the architectural team creating new house designs, as well as on-site with the builders, to making presentations to Parish Councils and negotiating with planning officers.
Oak frame extension costs
As with any extension costs, oak frame extension costs are generally dictated by the final size, design, features and particular requirements of your project.
The amount of glazing specified is one example of where costs can escalate. Introducing large sets of bi-fold doors, as opposed to a simple set of French doors, will naturally add to the price, so too will factors such as the complexity of the extension and the location of the build.
Access to the site can also present issues and extra costs, as a crane is commonly used to erect both the frame and the SIPs (if used). However, where access is limited, there are solutions. "Difficult sites often involve specialist lifting equipment – occasionally the oak frame has been craned over the house, and there is lifting equipment available that can fit through the space of a garden gate," says Paul Brierley of Paragon Oak.
"Costs can vary greatly per m2," says George Allen, "but I would cost for between £3,500-£5,000 per m2 for an oak framed extension. If you're looking for a way of reducing costs, single storey pitched roof extensions with clay tiles are probably the most cost effective option," he adds.
Although it should be noted, says Paul Edmunds, that as with other extensions, on a pro rata basis, "a single storey extension can more expensive, as the foundation and roof costs are the same as a two storey extension."
Another element that can influence price is the type of oak used he adds. "Depending on the style and content of the oak used, the price can vary considerably. There are however options to use a hybrid system using oak and softwood timber framing which is proving to be very popular."
Pros and cons of oak frame extensions
Benefits of an oak frame extension
In general, design characteristics, speed of build, cost effectiveness and the sustainable nature of timber are all front runners in the list of benefits of oak frame extensions.
"A bespoke oak frame doesn’t just provide structure for your home," says project consultant, Dan Wilson at Carpenter Oak. "Because it will be visible within the extension itself, the timber also brings character, texture and warmth to your home. It will only ever improve with age.
"Oak frame extensions are also generally less ‘heavy on the eye’," says George Allen. "Options such as face glazing really give the sense of allowing the outside in, and are perfect for enjoying the outdoors all year. In addition, oak is a natural material and contains embodied carbon making it a great option for those looking for eco-friendly ways of building.
"Having a solid roof, will also allow you to keep the roof cool in the summer," adds George, "and the fact that the frame needs to be well insulated will keep the extension as warm as the rest of the home during the winter."
Drawbacks of adding an oak frame extension
When it comes to cons, there are of course some, but most of them can be overcome.
Oak is a natural material and even with offers of ‘dry’ oak, the timber will still crack and move slightly – but it’s not a structural weakness, simply a feature of the wood. Due to the shrinkage of the oak, glazing between the oak frame is an area that requires particular attention, but this is where face glazing can be worth considering when choosing windows for your oak frame extension.
Likewise, if you are looking for vast expanses of glazing with minimal posts, an oak frame extension may not result in the final look you are hoping for. If this sounds possible, you may need to consider other options such as glass extension ideas.
FAQs
Do I need planning permisson for an oak frame extension?
As with any extension, regardless of construction system, an oak extension must comply with planning rules. Fortunately some extensions do not need planning permission – the work could fall under Permitted Development.
“It is very important to speak to the planning authority regarding size, style and specific requirements and policy restrictions – some extensions may not actually need planning approval but some houses will have lots of conditions and restrictions,” recommends Merry Albright.
What time of year is best to build an oak frame extension?
"The advantage of the manufactured oak frame sections, means the kit can be manufactured in controlled conditions in the factory," says Paul Edmunds. "This subsequently reduces the site time and means an oak frame extension can be protected from the elements in under two weeks."
"I would suggest try to avoid winter if you are knocking through an external wall," adds George Allen. "However, if you plan to access your extension through existing doors you have more flexibility. If you start in early spring you should have a finished build by late summer!"
Our final tips for getting your oak frame extension project to completion? As there are a number of contractors involved in building one, good communication between all parties is key to keeping the build on track.
Ensure that there are no long delays between the groundworks being completed and the oak frame being delivered to site and erected. With the opportunity to include lots of glazing in an oak frame extension, make sure you have also considered ways to make your extension work with your garden.
For more inspiration, find out how these homeowners transformed their cottage with oak frame extensions.
