Moisture Content And Seasoning

As a tree is a living organism, the weight of water within it is frequently greater than the dry weight of wood itself. The water content of a tree is equal in winter and in summer, but one advantage of winter felling is that there is a reduced level of insect and fungal activity. After felling, the wood will loose the water held within the cell cavities without shrinkage, until the fibre saturation point is reached when the cells are empty. Subsequently, water will be removed from the cell walls, and it is during this process that the timber becomes harder and shrinkage occurs. As cellulose is a hygroscopic material, the timber will eventually equilibrate at a moisture content dependent upon the atmospheric conditions. Subsequent reversible

Table 4.1 Standard sizes of softwoods and hardwoods

Standard sizes of sawn softwood (20% moisture content) to BS EN 1313-1: 1997.

Table 4.1 Standard sizes of softwoods and hardwoods

Thickness (mm)

Width (mm)

75

100

115

125

138

150

175

200

225

250

275

300

16

V

V

V

V

19

V

V

V

V

22

V

V

V

V

V

V

V

25

V

V

V

V

V

V

V

V

V

V

32

V

V

V

V

V

V

V

V

V

V

V

38

x

x

x

x

x

x

x

x

x

47

x

x

x

x

x

x

x

x

x

50

x

x

x

63

x

x

75

x

x

x

x

x

100

x

x

x

x

x

x

150

x

x

x

250

x

300

x

Sizes marked with a tick indicate preferred EU sizes.

Sizes marked with a cross are the complementary UK preferred sizes.

Sizes marked with a V are the additional UK customary sizes.

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