Oak remains perhaps the most iconic of British hardwoods, but how does English oak fare against imported oak, and do designers and specifiers fully understand and appreciate the available choices and advantages of English oak over imported timber? Tom Barnes of Vastern Timber looks into the heart of this most British of woods.
Oak from English forests has been used in building construction for many centuries and original oak beams continue to support structures more than 500 years old. The traditional popularity of English oak can largely be explained by the availability of the trees and durability of the wood. As a natural building material, oak is extremely hard to destroy; large sections will resist fires intense enough to melt metal and will flex to accommodate the natural movements of a building.
Although English oak stocks have been depleted over the centuries, there continues to be a healthy supply of logs from private estates and, to a lesser extent, the Forestry Commission. With an increasing emphasis on sustainable forestry and general good practice among forest owners, oak forests will continue to be a productive part of the landscape in this country.
Vastern Timber has a vast amount of experience in supplying structural oak. A third of the company’s business is in supplying oak beams, so the company has a particular passion for English oak. The company recently supplied English oak to restoration work at the Tower of London and the reinstatement of a drawbridge which dates back to 1834, as well for the production of furniture for the restoration of the iconic Chapel Royal of St. Peter ad Vincula. English oak is ideal for use on projects such as the drawbridge as it is extremely robust and the new structure will undoubtedly last for centuries. English oak (Quercus robur) is considered to be the strongest of the oaks because it has a more interlocking grain than oak from continental Europe which is characteristically more mild and straight grained.
Oak beams are usually cut from trees between 90 and 120 years old, ideally felled during the winter when the sap is down. The beams for construction tend to be fresh sawn or ‘green’, which means that they are in fact wet, and while this is of concern to many architects because of oak’s natural tendency to shrink and split, it is the ideal way to use the timber. The alternative, dry oak, is very hard and therefore more difficult to work.
Oak dries very slowly (a large beam can take 8 – 10 years to fully dry) and is consequently expensive. However, there are four options for the dryness of the timber, and this will have an impact on the price. Kiln dried oak beams (moisture approx 15%), air dried oak beams (moisture approx 25%), semi seasoned / weathered structural grade oak beams (moisture approx 20% – 60%), and finally fresh cut structural oak beams cut from old felled logs which have been ‘settling’ for over three years (moisture – wet). Fresh sawn beams are available up to 9.5 metres long, and up to 500mm x 500mm section size.
For designers looking to specify structural oak there are two main sources – The UK and France. However, while imported oak can often be cheaper, particularly when taking into account the embattled Euro,, there is a sustainability price to pay if the wood is imported. There is also a great deal of difference in design flexibility. Local British sawmills are easy to access, and as well as the option to inspect timber and cuts before choosing, the designer will benefit from more flexibility in cuts from their local sawmill, especially curved and shaped wood.
But it is the issue of sustainability which ultimately dictates that English oak is the better and more responsible choice. The British timber market has for a long time suffered against foreign imports. Ninety four percent of all hardwoods used in the UK are now imported. This has resulted in an industry being hard hit and communities also being impacted as a result. This has, in turn, had a negative effect on the management of our own native forests and woodlands which, without a strong domestic timber industry in support, has consequently suffered from lack of adequate management. Studies indicate that up to sixty percent of our native mixed woodlands are currently unmanaged.
However, with growing momentum of the Grown In Britain movement that aims to promote the benefits of British grown timber, as well as supporting better management of native forests and woodlands, the reality for architects and designers specifying structural oak is that there are more good reasons to buy British than not to.
As seen in Architect’s Datafile