Oak Frame: Experts' Views

“The Oak Revival Owes its Success to the Demand Created by Self-builders”

Mark Brinkley, H&R's building expert and author of The Housebuilder's Bible, explains why the British public have such a love affair with oak, and offers an insight into the oak framing industry.

Oak has an enduring fascination for British self-builders, and far from peaking, it’s a trend that’s still growing. What many people don’t realise is that this oak revival is quite recent and owes much of its success to the demand created by self-builders.

It’s not a cheap way to build, for two reasons: firstly, you are using a post and beam construction form, which is economic for office blocks, but much less so for low-rise housing, where the walls are quite capable of carrying the loads imposed on them. Secondly, you are using oak, which is one of the more expensive timbers you could choose. People building in oak are not trying to save money.

And it’s not really speed that is the attraction either. Almost all the innovations which have happened in the housebuilding arena in the past generation have been based around the notion of decreasing production time and labour costs. Not so for oak. For even though oak construction is the original factory-made product, it takes lots of time and skill to put together in the workshop. And having done that, it then gets dismantled, shipped to site and erected all over again. Oak houses aren’t especially slow to construct, but they don’t sell themselves on being quick either. What you are paying for is quality. Oak is a building system which has stood the test of time — you are buying a piece of history.

All oak frame housebuilders offer a bespoke service. Some are little more than one-man bands, whilst others are now well-established design and build businesses. 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 it 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 oak itself is always worked ‘green’ — within a couple of years of felling, when the moisture content is still high. After four or five years it becomes so hard that you can no longer cut it or machine it. This drying out period is also associated with high shrinkage and this 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 alignment over time.

Whilst much of the skill remains rooted in the 16th century, the finished product has to meet the demand of the 21st, meaning oak frame homes must be well insulated, weather - tight and (increasingly) airtight. So, the typical new green oak home includes a fair amount of hi-tech materials like air barriers, EPDM tapes and flexible gaskets around the joinery.

"Success is Simplicity"

Pete Tonks, Chief Designer at TJ Crump Oakwrights (oakwrights.co.uk) Pete also runs PJT Design (pjtdesign.co.uk).

When it comes to designing in oak, forget all you have previously learnt, says Pete. Here are his top design tips:

• When planning room layouts, try to work this into a grid, as the success of an oak frame design is in its simplicity.

• Get your dividing walls to align wherever possible within this grid layout.

• Oak frame designs generally work on the principle of ‘bays’. Keep them between 3.5m and 4.5m apart; any larger will require overlarge sections of oak.

• The extra wall thickness outside of the oak frame across the overall width of the building could be between 600mm and 1,000mm; allow for this in the design.

• Keep any clear openings (i.e. for sliding doors) to a maximum of six metres to avoid the need for additional steel beams.

• If creating a historically correct oak frame building, then aim to design your roofs at 47.5° using a combination of straight gable-to-gable connections.

• Hips, valleys and other complex roof forms are more expensive than simple linear ones; likewise dormers are more complex and expensive than rooflights.

• The simplest and most cost-effective way to construct your roof space would be to use a conventional oak truss with a horizontal tie (collar) at the base.

"Pare Back the Structure"

Roderick James, Principal of Roderick James Architects LLP (01803 868000, rjarchitects.co.uk) looks at the design benefits of oak for creating contemporary homes

• Oak frame construction provides the characteristics of open plan living — fun, light and dramatic spaces. It also allows for flexibility over internal layouts.

• The method of construction provides for efficient thermal ‘envelopes’ using sustainable materials.

• Whilst a traditional frame will have main frames, purlins, ridges and exposed rafters, a contemporary frame will allow a designer to ‘pare back’ the structure to a minimal ‘principal frame’ design — offering cleaner lines.

• Where budget is an issue, Douglas fir or bolted timber frames can prove a lower-cost alternative to oak.

• Contemporary designs can incorporate stainless-steel bracing and connections, marine architecture and engineering, simpler framing, curved roofs and so on.

• A shallow-pitched or curved roof will lend itself more to zinc, copper, lead or moss sedum roofs, rather than the more traditional slate and clay tiles.

• Versatility is a key advantage; flexibility over window positions, cladding material, wall, floor and roof — a frame can blend with any location, as walls may be clad in timber, stone, brick, render or slate.

"Celebrate Oak's Natural Beauty"

John Greene, Border Oak's Managing Director (01568 708752, borderoak.com) recalls his part in reviving oak frame and offers some tips.

I designed and built my first green oak frame in the late 1970s (pictured at top of page) — at the time people thought I was a bit eccentric to try and revive a craft that had been dormant for 250 years. So when I set up a business making oak frames for others, people just thought I was mad! Luckily there were a handful of spirited self-builders who shared my passion for oak and had enough trust and faith in me, and the material, to commission their own homes. Thankfully, the self-builders (and builders) I have worked with over the last 30 years have always approached oak framing with an open mind. This has been crucial to Border Oak’s success and has played a significant part in transforming oak framing into a mainstream building choice. There are no ‘rules’ for oak frame design, but here are some guidelines:

• An exposed frame with rendered panels will struggle to carry a contemporary design, but an aisled frame could embrace modernity.

• For a traditional design, look closely at Mediaeval buildings — don’t tamper with the spacing of the beams or add random pieces of oak for an authentic look. Post and beam is a modern conception and will not look right.

• Contemporary oak frames needn’t adhere to rigid criteria — breaking convention is part of the intention, but avoid historical trademarks, such as jetties.

• Oak frames generally look best if structural, rather than decorative. The section size and joints of a decorative frame need to be ‘true’, to avoid looking pastiche. Overcomplicating the oak frame can look chaotic and fussy. Celebrate the natural beauty of the material.

• Vernacular, local proportions and external materials are very important in anchoring the building to its surroundings.

• Gable ends can look cumbersome if they are wider than 6.8m (unless the height of the building can be proportionally raised), creating an ugly roof pitch or a huge gable end.

• Add extra floor area in adjoining units, called ‘bays’, rather than stretching dimensions.

• Disguise size and volume with dropped ridges and a change in material, with projections in the façade and interplay with the plot.

• Masonry, SIPs and softwood frames are all suitable partners for oak.

• Detail is paramount — rounded, chamfered jetty feet, curved braces, draw-knifed posts, and carpenters’ marks all contribute to the success of the frame but are often eradicated with mechanical production. The touch of a carpenter is significant.

More Advice on Oak Frame:

• Oak Frame: Design Masterclass
• Oak Frame: Design Solutions
• Oak Frame: Frame Types

Oak Frame Self-Builds:

• An Oak Framed Self Build in Oxfordshire
• A Three Bedroom Oak Framed Home
• An Oak Frame Cottage Built for Under £300,000