It’s rare to open a copy of Homebuilding & Renovating these days and not find a case study featuring the use of oak somewhere, and its appeal seems to keep growing. What many people don’t realise is that this oak revival is relatively recent and owes much of its success to demand from self builders. Oak building today is an unusual mix with very traditional techniques combined with very modern materials. Here are some of the common issues.
Isn’t it expensive?
Of course it is. You don’t have to use timber post and beams to hold a house up — there are much cheaper ways of doing it. And oak is one of the most expensive timbers you can use. People don’t build this way to save money. Oak framed homes tend to cost upwards of £1,400/m² – maybe 30% to 50% more than developer standard – although it’s possible to build one for as little as £1,000/m².
Why use oak?
You don’t have to. Post and beam homes in other countries rarely do. In North America, they usually use Douglas fir or some other softwood species, and there is no reason why you can’t use something cheaper than oak. But the British market has developed a preference for oak because it was the traditional material used in Tudor times. There is something about the look, feel and smell of oak which is innately appealing to both traditionalists and modernists, and people love the fact that it’s such a naturally long-lasting material.
This pretty Border Oak cottage was built for just £168,000
So just how much oak gets used during construction?
Oak trees are harvested when they are around 80 years old. Each one will produce roughly 15ft³ (cubic feet) of construction-grade oak. The typical oak-built family home uses 800ft³ of oak — the produce of around 50 trees. Almost all of the oak used in British green oak homes is sourced from sustainable plantations in France and Germany, with companies replanting many trees to compensate. English oak is available but it’s more expensive and it tends not to grow so tall and straight, which makes it more suitable for furniture than construction. The species is identical.
Why is it sometimes referred to as green oak?
Newly felled timber is referred to as being green because it has a high moisture content and it’s much easier to work. With oak, you have to work it in its green state because, after four or five years, it becomes so hard that you can no longer cut or machine it. Much of the skill in working with green oak is to know how the timber will shrink and to make the joints so that they get tighter as the timber hardens.
Internal beams are a major draw for most oak lovers, offering the ability to create impressive vaulted ceilings such as this
How do the builders cope with the oak moving?
This is one of the key skills involved with designing in oak. During its first few years, oak shrinks by as much as 5% radially (that is across the grain), but the length of each piece remains the same. Good designers will take this into consideration when putting frames together. However, when detailing the joints connecting the posts and beams, the shrinkage factor is used to make the joints tight. The pegs used to fix the joints are always tapered and the holes between the timber are normally offset, allowing the shrinkage to gradually draw them into a strong alignment over time.
Another area where shrinkage is a factor is glazing and joinery. Oak builders have become adept at designing weatherproofing details which can cope with a backing frame which is set to shrink.
Oak framing has changed dramatically over the centuries. Whilst the essence of building in oak is traditional and timeless, many of the solutions needed to make it suitable for the 21st century are surprisingly hi-tech, with heavy use of stainless steel fixings and EPDM tape.
This Border Oak self-build incorporates SIPs for improved energy efficiency and is weatherboarded for a more contemporary finish
Who builds oak homes?
Border Oak started the oak revival in the late 1970s — before that there had been very little oak used in new buildings for 300 years. Their success has led to a proliferation of cottage businesses, mostly based in the west of England and the Welsh borders.
How do these businesses differ?
All oak framed housebuilders offer a bespoke service. Some are very small, little more than one-man bands, whilst others are now well established as design and build businesses, catering mostly to the self build market. Perhaps the biggest difference between them is whether they use machine cutting or stay with traditional handmade work. Computer-controlled cutters are faster and potentially more accurate, but they usually require the oak to be planed beforehand, which gives the wood a rather different look. On the other hand, machine cutting can sometimes achieve levels of complexity which would not be easy to replicate traditionally.
The designs can also vary from traditional, Tudor-style farm houses and cottages to stunningly contemporary, open plan homes, with lots of built-in glazing. Some businesses specialise, others are happy to work in any style.
Oak posts can create a natural divide in open plan spaces
I love the look of oak but I’m not sure I can afford it!
It doesn’t have to be all or nothing. Where oak really comes into its own is in large open plan spaces, especially ones with vaulted ceilings. There is nothing to stop you going for a conventionally built home and adding an oak framed extension, enabling you to get the ‘wow factor’ on a budget.
What Are the Associated Problems?
Much like any other form of construction, oak frame carries its own inherent, potentially problematic, properties, but being aware of these from the start will stand you in good stead to eliminate any difficulties. First of all, with oak you’ve simply got to love beams, and accept that they will get in the way sometimes and that you’ll have to design around them. There’s also a limit to the room’s open depth without encountering a post: around 4.5m. Internally, oak can be difficult to light, especially with vaulted ceilings, so lighting design needs to be factored in early on. When building, the foundations tend to have to be very precise; a mass concrete strip footing is normally used, with a dwarf wall above. On the plus side, oak is very well suited to sloping sites.
The use of oak can also be extended to outbuildings, such as this garage and office space from English Heritage Buildings
“We love the character of oak”
Graham and Annie Boon chose an oak frame by Border Oak for their site in Oxfordshire. “Oak gives instant age and character, and a new oak framed house like this has all the advantages of modern insulation and comfort and none of the disadvantages of old oak framed houses,” says Graham. The house came in at a reasonable £950/m², with the couple keeping costs down by carrying out a large amount of labour themselves.
Getting the Best from Oak Frame
Paul Edmunds of Welsh Oak Frame offers tips on ensuring the project runs smoothly
Ensure your designer fully understands your objectives. A good relationship in the early stages will enable the optimum solution to your brief in terms of design, cost, performance and aesthetics of your oak frame. Features such as lighting in vaulted roof areas and special inglenooks can be easily incorporated if factored into the project early.
Make sure that your oak frame company has the necessary accreditations in place. TRADA is widely accepted as the industry leader in timber framing standards, which provides assurance that a line of recourse is in place should any problems arise.
Good communication between your contractor or subcontractors and your oak frame company is a must. Details for areas such as foundations, window and glazing fixing, warm roof structures and weatherboarding should be readily available to you.
Oak frame doesn’t need any special or time-consuming maintenance. A light oiling of the frame internally will give it depth and a gentle lustre but it’s not essential.