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Tim Crump describes Oakwrights houses as “country contemporary” – a modern design softened by the oak frame

In the frame
Published:  19 February, 2010

Oakwrights’ “try before you buy” show home is an expensive luxury, but one that pays dividends

Green oak frame specialist Oakwrights combines traditional values with hi-tech production. Sally Spencer reports

If you fancy a short break in rural Herefordshire, there’s a self-catering house that might be just the ticket. And, if you enjoy the experience of living in this beautiful post and beam home, guess what, you can have one made to your own specification.

The house in question belongs to TJ Crump Oakwrights Ltd and offers potential customers a unique “try before you buy” opportunity to immerse themselves in the whole culture of oak framing, from soaking up the ambience of the house, to visiting the nearby workshop and seeing oak frames in the making.

“It’s an expensive luxury but it works very well for us,” said Oakwrights founder and managing director Tim Crump.
The show house incorporates a host of eco-friendly technologies, such as rainwater harvesting, ground source heat pumps, and Oakwrights’ patented WrightWall breathable panel wall system, which has a U-value of 0.19. It achieved an airtightness of 2.06 air changes per hour without any bother and the company is sure it can improve on that.
“It’s often a criticism of timber frame buildings that they’re not airtight, but it’s very easy to make them so,” said general manager Bill Keir. “The show house was something of a hobby project for us, so if we really set out to do it, we could achieve better airtightness. It’s all in the detailing.”

It’s an indication that while timber frame may look and sound traditional and low-tech, it can be anything but – certainly where Oakwrights is concerned.

Take the technology it uses, for example. Oakwrights’ oak frame design team upload the bespoke house plans onto Dietrich CAD/CAM software, which is specifically geared for heavy timber engineering. The designers then produce a 3D model, which not only results in a machinery cutting list, but also provides a virtual walkthrough for the client.
Once approved, the file is sent through to Oakwrights’ pride and joy, its Hundegger K2i beam-processing machine, bought as part of a £1m investment programme in 2008 and “the most advanced Hundegger in the world”.

It’s true that other timber frame companies have Hundeggers – in fact Oakwrights already had a K2, which it bought in 2002 – but it’s unusual for the German machine maker to build one for oak, rather than softwood, and unheard of for it to build one incorporating a third head specifically dedicated to tenon chamfering.

“It did cost an extra £56,000 to have that one head fitted,” said Crump, “but the frames look a lot better when they go out, even though you will never see those tenons [once the frame is erected]. God will know they’re there and so will I!”

Primary processing of the oak is carried out by “preferred supplier” sawmills, which deliver the resulting beams to Oakwrights cut to size and packed in sequence.

“It’s then checked and graded by Oakwrights' certified graders and we look at where each piece is going to go within the structure – for example, we need top quality for purlins, while studs can be a lower quality,” said production manager John Lloyd. “We also take the visual aspect into account, so we work out which face is going to be visible and if it can be turned round if necessary.”

The K2i cuts at 1m3 per hour and with great accuracy – to tolerances of plus or minus 0.5mm – and it’s a manufacturing process that Tim Crump says sets Oakwrights apart from many other oak frame companies. “People say their frames are lovingly cut by hand, which is fine, but when it’s been up for six months and it starts to shrink, which all frames do, you won’t be able to tell if it’s made on a Hundegger or by hand. But if it’s been made on the machine it’s much more accurate and the fit is much better when it’s erected.”

And, he added, “tricky work”, such as arched collar braces and other curved members are still cut and scribed in by hand.

Once the component parts are machined they move to the framing shop where they are dry fitted in two dimensions, although complex structures, such as roofs, are assembled in 3D in the yard. They are then disassembled ready for sending on their way to site.

Oakwrights can run five sites at once “at a push”, although three is preferred and the four-to-six strong erection crew includes the designers. “We go out to site to help put the frame up,” said Roland Horwood, senior frame designer/project steward. “We have detailed knowledge of how the frame should fit together, plus we can see if anything we’ve designed doesn’t work in the field quite as well as we thought it should.”

Framers from the workshop are also hands-on on site. “If they follow the frame through the whole process they have a better understanding of it and it’s no longer an abstract thing,” said John Lloyd. “Plus the client gets to make contact with someone who’s physically worked on the frame.”

Current throughput is about 1,400ft3 of oak per week, depending on product mix, resulting in about one 800ft2 house, plus assorted extensions, garages, summer houses and building components, such as roof trusses and floor sets, per week. “Two or three” Douglas fir post and beam frames are also constructed per year.

Post and beam frames are processed pretty quickly, while the more traditional style oak frames incorporating Oakwrights patented infill panels take a little longer. The panels comprise a 12mm WISA WBP plywood sheet, breather paper on the outside, then a neoprene membrane and a render bead and Compriband (an expandable butyl strip) edge system. A weather bar and lead tray are at the base of panel, with the lead tray coming up underneath the breather paper. Render is applied onto the neoprene membrane.

The panel is inserted into a groove cut into the frame by the Hundegger and is installed as the frame goes up. Polyurethane insulation is on the inside and a gap is left around the edge to allow for the installation of wiring
before being filled with Rockwool which expands to fill any gaps as the frame shrinks. The groove also houses an intumescent strip, which affords frame and panel a 55-minute fire resistance.

“On the more contemporary-style post and beam houses we use WrightWall, our new wrap system,” said Tim Crump. “It’s a hemp and compressed wood fibre insulated breathable wall system that we manufacture here as a closed panel and then crane onto the side of the house. The biggest panel we’ve done to date was 6m by storey-height – on a windy day, quite interesting!”

It’s this successful marriage of innovation and traditional values that has earned Oakwrights several awards and won it a stack of business – everyone wants to work with them, it seems.
The company worked with Fielden Clegg Bradley Architects and designed, made and installed the huge oak post and beams for the Accordia apartment building in Cambridge, which won the 2008 Stirling Prize for architecture. And in the same year, Oakwrights also won The Daily Telegraph Best Traditional Home category in the newspaper’s Homebuilding & Renovating Awards.

Ongoing collaborations include work on the Lower Mill Estate in the Cotswolds, where Oakwrights is on site constructing its seventh house for developer Jeremy Paxton. And it supplied a two-storey glulam frame for ZEDfactory’s modular RuralZED sustainable house kit, seen earlier this year at Ecobuild.

It’s just finished building an 8,000ft2 manor house in Chelmsford and, its biggest project to date, an 8,000ft2 above ground and 5,000ft2 below ground mansion in Westerham is something of a flagship in its portfolio. Perhaps the best houses to work on recently, however, were the six “ultra contemporary” houses in Rock in Cornwall – thanks in part to the post-work surfing opportunities.

Oakwrights is celebrating its 10th anniversary this year and plans to continue to maintain its strong order book by “always moving forward”. 

“In the future we may look at offering more of a package [beyond the frame erection] to customers to increase our turnover,” said Crump.

In the framing shop frames are hand scribed and dry fitted in two dimensions

Oakwrights can erect frames on five sites at once at a push