Oak framing is a time-honoured building method which is enjoying a relatively recent revival and is a firm favourite with selfbuilders.

Oak framed houses have long been admired for their beauty and structural integrity, and building a new oak framed house would seem to offer the perfect compromise – combining modern building materials with the instant character provided by exposed beams and timbers.

This slow-growing wood has a tight grain which makes it durable, strong and a natural insulator. In fire, a protective layer of charcoal forms around the outside of an oak beam, delaying damage to the core, and most oak frames are sturdy enough to withstand the ravages of a tornado.

At least a 200 year lifespan is an achievable target for a well designed oak frame – long enough for forests to regenerate – which makes it ideal for sustainable housing. Large timbers retain high value and can be re-used singly, or the whole building can be re-sited and, ultimately, will decompose when eventually redundant.
Untreated oak weathers to a silver grey colour externally whilst remaining deep golden inside. As the oak seasons it hardens to a nail bending density, so carpenters tend to work the wood while it is fresh and unseasoned. Oak is described as ‘green’ when it has been felled only a couple of years and the timber still has a high water content and is not dry in the middle.

Fresh green oak gives off a wonderful woody aroma, but can act as a magnet for flies who like to hibernate in the shakes. A much more expensive alternative is air-dried oak, which is already semi-seasoned and therefore less pliable and easy to work, but most new houses are built using green timbers.
It then takes between five and 10 years for an oak beam to dry out completely and season, and this process often results in shrinkage and movement – a factor which can alarm unwary homeowners. As the oak dries and shrinks the process creates minor splits or ‘shakes’, which are all part of the building’s charm but can cause a few creaks and groans to emanate from the timbers!

DESIGN OPTIONS

While the carpentry of frame design was already highly developed by the medieval period, other modern technologies such as insulation, glazing and frame infill techniques, far outperform their historic counterparts. This enables the modern designer to utilise the beauty, strength and integrity of the frame to its full effect, creating open-plan living spaces without the need for internal structural walls. Its versatility can be exploited in great open-plan spaces, soaring vaulted ceilings, galleries and atriums, adding to the sense of openness and suffused in natural light.

Many selfbuilders are unaware just how flexible the design service offered by oak frame companies can be. They assume that they will have to build one of the standard house types shown in the brochure, but these tend to be a sales aid designed for guidance rather than a limited selection.
Oak frame companies offer a portfolio of designs which can be adapted to create individual houses, and many have in-house designers and architects who will produce bespoke plans and elevations, including detailed drawings for building regulations. It is possible to build very contemporary homes around an oak frame and, if a structural engineer specifies additional steelwork to reinforce the building, this can be concealed in the oak.

Alternatively, traditional English frames are based upon the design and style of the vernacular oak frames found in English towns and villages. There is no county in England without examples of oak framing, and this can sometimes be extremely useful in persuading planners to grant planning permission.
An increasingly popular option is the barn-style oak frame, which combines a mixture of the contemporary and the vernacular. The essential difference is that the beams are not generally exposed externally. These buildings invariably have a more open plan feel, with fully vaulted roofs, and the heavy oak frames are well suited to accommodating large areas of glazing. External finishes can be a combination of infill panel insulation and external cladding.

AT THE FRAMING YARD

Many oak framing companies have adopted traditional framing techniques, passed down through generations, with hand tools still very much in evidence. Others favour fast computer-controlled cutting machines, which – although disliked by purists – can achieve levels of complexity and accuracy difficult to replicate by hand.
Individual trees are still chosen to make specific parts of the building, and the wood is used soon after it is felled so that the green timber is easy to cut and work into the desired shapes. Most modern day companies buy European or English oak ready sawn from timber merchants, although there are a few companies who run their own sawmills.

Green, unseasoned oak is traditionally assembled with classic wooden pegged mortise and tenon joints, and the timber continues to contract – tightening the joints to give a uniquely strong structure. The finished building will also need to incorporate modern materials such as air barriers and flexible gaskets in order to meet modern day building regulations. Most companies will frame up the entire frame at their framing yards prior to disassembling it ready to be delivered and re-erected on site.

ON SITE

It is important to find out the lead-in (waiting) time for your oak frame because these vary enormously between companies and could hold up your build. Some package companies will undertake everything from gaining planning permission and erecting the frame to organising subcontractors and completing the entire project on your behalf. Others will simply supply and erect the oak frame, leaving the self-builder responsible for organising everything else.

Foundations must be accurately completed before the frame can be delivered, so ensure you leave plenty of time for unforeseen problems at this stage. Oak frames need a flat surface, and poorly built foundations are a frequent problem for all types of timber frame. It therefore pays to employ experienced groundworkers.

Make sure that access will not prove a problem for a crane, which will be required to winch the huge trusses and cross sections from the lorry. Erecting the frame will then take several weeks depending on the weather, the size and complexity of the frame and how many men have been allocated to the job.

Once the frame has been built the timber stud infill panels and insulation can be fixed in place, and the shell clad with materials traditional to the local area, such as brick, stone, weatherboarding or render. Structural Insulated Panels (SIPs) are a modern alternative to a timber stud wall – manufactured in a controlled environment and shipped to site ready for erection. They consist of an inner ridged insulating core of expanded polystyrene (EPS) sandwiched between two outer skins of oriented strand board (OSB), and provide high levels of thermal efficiency.

Initially, oak frames are susceptible to a degree of shrinkage and movement and, to minimise the effects of this, many companies prefer not to expose the oak externally. This allows them to completely insulate the frame, minimising the cold bridging effect of the timbers and providing a draught-free environment.

The current preference is for the oak frame to be as exposed as much as possible internally, and to be left natural – treated only with linseed oil or beeswax if a soft sheen is required. Oak, unlike many other timbers, does not require preservative because the wood is naturally resistant to insects and weathering, although the frame will become stained from the tannin which seeps from the wood. This will wash off in the rain, or can be removed using brick acid or sandblasted once the frame has been built.

Whether renovating or building from scratch, it is recommended that you use traditional materials such as lime mortars and plasters, which allow for minor building movement. Hydraulic lime mortars are particularly useful in timber frame buildings because their excellent vapour exchange properties minimise rot and damp while providing good weather resistance.

COSTS

Oak framing is often seen as an extremely expensive house building option, with oak costing around one third more than other timbers. In general, the cost of the frame usually equates to 15-30 per cent of the total build cost. Resale values are correspondingly high, however, and there are ways to reduce costs and ensure that you get maximum value from the exposed frame without breaking the bank.
One option is to combine this form of building with a less expensive alternative, such as blockwork or softwood studding. By building just one section of a house using an oak frame you can benefit from all the advantages of the wood in prominent areas which really matter, such as hallways and sitting rooms. Known as ‘hybrid’, this method is ideal for those on a limited budget who wish to feature some oak within their home.

An oak frame is worth a considerable amount of money and, understandably, most suppliers require either a substantial deposit or full payment when the order is placed. This can present cash-flow problems to the selfbuilder, however, who would normally never agree to pay for any services or materials up front.

RESTORING OLD FRAMES

Timber framed buildings are totally functional. Every component part of the frame serves a purpose in taking a load or a stress to keep the whole structure in equilibrium, which is why the members of a frame should never be removed or cut through. Apart from destroying the completeness of the structure this disturbance will set up new stress patterns and may cause settlement, cracking of finishes or infill panels, failure of other members and serious instability.

It is therefore essential to understand how your building works and to remember that it is a framed structure, with its forces and loadings carried on the comparatively slender timber members of the frame. If you are repairing a timber framed building you are strongly advised to seek professional help as it is not a job for an amateur.
The Society for the Protection of Ancient Buildings advises that it is only necessary to disturb the timbers of an old oak framed building if it is absolutely vital to ensure the survival of the building. Gentle, sensitive repairs will ensure that the oak timbers retain their character, cleaning should be done by hand and no mechanical tools should be used.