Answers to questions we’re often asked by customers and people interested to know more about what we do. If you have a question you’d like to ask Altham Oak’s professional team, please email [email protected] and we’ll respond as soon as we can.
Where can I use green oak?
Green oak is traditionally used in the roof structure and for floor and ceiling rafters and beams. Care should be taken when using green oak in certain cases, e.g. lintels, where it’s required to directly support masonry. Typical cement masonry is brittle and can crack as a result of the natural shrinkage that occurs as the green oak dries. As an alternative, steel or concrete can be used as a support, with the oak used as an eye-catching facade.
What types of finish are available?
Please see our page on Surface Finishing for all the available options.
Builders may make my oak dirty – can I wrap it in plastic to keep it clean?
Covering beams in a fashion that doesn’t allow adequate ventilation will result in mould growth, as condensation will form on the plastic. A better solution is to wax the oak to allow it to be cleaned more easily later.
How can I stop oak for external use turning grey?
You could paint it, but this defeats the whole point of paying for oak. Microporous paints and stains will require periodic maintenance and re-application as they start to break down after a year or so. Grey can be sanded away before further coats are applied but we would advise allowing the oak to go grey. The grain is still visible and the oak is more durable than other timbers, even if left exposed in its natural state.
What happens to the oak as it dries?
Clean grained (i.e. with no large knots) green oak doesn’t shrink appreciably in its length but does in section. You can expect green oak, in a centrally heated space, to shrink by between four percent (across annular rings) and seven percent (along them) on average. This will mostly occur during the first season of heating. Above a fire or underfloor heating, these percentages are increased, while outdoors the shrinkage is much less.
Shrinkage rates differ throughout the depth of the timber, which causes the familiar splitting appearance of an oak beam. Oak dries out more quickly from the end grain than the side grain, leading to splits at the ends. It’s hard to eliminate completely but can be minimised by coating the end with wax to reduce evaporation, for example. Cracking is unavoidable and has been allowed for in the structural calculations.
How much will my beam weigh?
When the oak is green, 1161kg per cubic metre, or 35kg for every 300mm cube. In imperial terms, this equates to 70lbs per cubic foot. E.g. a beam 3 metres long with a 225mm x 100mm section will weigh 76kg (167 lbs).
Handling Assembly and Installation of Trusses and Frames.
Click this link to open a pdf file OAK TRUSS HANDLING LIFTING AND ASSEMBLING