Whilst the majority of oak used for construction is green (wet), dry oak beams are used when it is critical that shrinkage and movement of the beams is minimised, such as for floor joists. We stock dry oak beams, seasoned and semi-seasoned beams, and we offer a range of moisture categories to suit various projects.
Species
Quercus robur
Moisture content
Various from 15% upwards
Surface finish
Sawn or planed
Sections available
Max 100mm thick for KD. Max 150mm for AD. Various for semi-seasoned. Up to 6.0mt x 400 x 400mm for old-felled.
Dry/Seasoned Oak Beams
Species
Quercus robur
Moisture content
Various from 15% upwards
Surface finish
Sawn or planed
Sections available
Max 100mm thick for KD. Max 150mm for AD. Various for semi-seasoned. Up to 6.0mt x 400 x 400mm for old-felled.
Grading
Graded under BS5756
Grades available
Visual grade & Equivalent mechanical grade
TH1 D30
Top grade for sections equal to or less than 20,000mm2.
TH2 –
Lower grade for sections equal to or less than 20,000mm2.
THA D40
Top grade for sections of more than 20,000mm2.
THB D30
Lower grade for sections of more than 20,000mm2.
Durability
BS EN 350 Durable (Heartwood only)
Weight
Approximately 850KG / M3 when air dried and 700KG / M3 when kiln dried.
Shrinkage
KD
None
AD
Negligible
Semi seasoned
Dependent on age
Old felled
Less than 0.5% along the length. Between 5% and 7% across the section.
Modulus of elasticity
Kiln dried oak E = 10,000 N/mm2
Air dried oak E = 9,000 N/mm2
Old felled oak E = 8,000 N/mm2
The more dried oak gets, the harder and more difficult to work it becomes. Dry oak will blunt tools quickly.
Oak contains tannic acid which will corrode ferrous metals. When the two come into contact, a blue sludge is formed which will stain the oak and anything else it comes into contact with. This is less of a problem with kiln dried wood.
The ambrosia beetle can attack the wet timber (30% moisture +). However, the beetle will die as soon as the wood dries to less than 30%. Re-infestation will not occur. Other dry wood will not be affected. Sapwood is commonly attacked by the powder post beetle (Lyctus spp). However, sap is normally excluded from oak beams.
All fixings used in conjunction with green oak should be stainless steel.
Surface spread of flame class 3 (BS 476-7)
Trada Technology. www.trada.co.uk
Vastern Timber is not able to offer structural engineering services or advice on section sizes required for particular applications.
While the utmost care has been taken to provide accurate information, Vastern Timber shall not be held responsible for any consequences arising from any errors or omissions on this website nor for any damages resulting from the use of the information.