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Oak Beams - Technical Information

STRUCTURAL BEAMS

If required to grade beams specified for structural use the following visual grading scheme is used:

(These specifications are drawn from BS 5756 VISUAL GRADING OF TROPICAL HARDWOOD adapted to allow for the characteristics of English Oak):

  • Colour variation allowed
  • Knots - no greater than 1/3rd the face width
  • Slope of grain - no greater than 1 in 11
  • Splits are an inherent part of the character of oak beams. The slope of grain specification makes splits occur generally along the beam and they are not considered a problem.
  • At time of delivery - any surface crack allowed
  • At time of delivery - splits to the heart allowed. Splits deeper than this but not right through limited to 1.5 ? width or 0.2 ? length of the beam.
  • Splits right through only allowed for 1 width of the beam at the ends.
  • Sapwood allowed
  • No rot except soft knots, which will be removed to check the situation. Considered to be a natural feature.
  • Wane on any corner no greater than 1/4 the face width, unless there is a corresponding increase in dimension.

hand sawm oak beams

HAND CUT OAK BEAM

All timbers are sawn to the agreed dimension, variation 13 mm (1/2”) under to 26 mm (1”) over.

Usually beams will be cut to within 26 mm of a flat plane on their upper surface and cut to follow the grain of the tree on the other faces. This must be specified depending on the use.

If cutting to follow the grain involves bends in the plan of an oak beam, timber will be balanced around a centre line.

Sufficiency must also be judged in the contexts of tradition and usage.

Floor joists will be cut to the above specification but the upper surface may need to be of greater accuracy.

Specific oak bends or oak beams to match existing can be provided.

The general opinion of structural engineers is that English Green Oak to the above specification should achieve SC5 grade.

Oak beams become significantly harder and stronger as they dry.

BANDSAWN OAK BEAMS

Cut to the specified tolerance to within a standard deviation of ? 5 mm.
All sides cut square and straight, however some movement will occur as internal tensions in the wood are relieved by sawing and further drying. This adds some character to the wood in time.
If needed, we can grade bandsawn oak to remove the extremes of this irregularity.
Tapered and crowned beams can be cut, and also bandsawn bends.

COLOUR

Fresh cut oak is pale yellow quickly darkening to a tawny colour.
Heartwood is clearly darker than sapwood. Within 6 months of outdoor sunshine, oak will have begun to turn a silver grey colour due to ultra-violet degradation of the surface. If unfinished, our beams may be grey, yellow or a mixture. All air-dried beams will be grey. Should a uniform appearance be required our beams must be “finished” by adze or machine adze.

RIVEN BEAMS

Contact us for more information on riven beams and other products.

 

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