• Note the markings on the ends of the timber. Make sure that they are marked as required by SABS, i.e. there must be at least an 'S5' mark at one end and a mark on the other end indicating from whence came the wood. (S5 indicates that the working strength is at least 5 Mpa in bending).
• If there are no markings, consider the wood to be inferior.
• If the mark indicates that the timber comes from another Province, view the timber with suspicion as it could well be Pinus Patula, eminently suited for furniture, but of relatively low density species inferior to Pinus Radiata, which grows mainly in the coastal regions of the Cape (Radiata is arguably the best pine species in the world and we are fortunate in the Cape to have a type of Radiata that is far stronger than that found in Australia and New Zealand).
• Having ascertained that the timber is Radiata and is marked, take care to avoid any piece that contains pith. Low density surrounds the pith, which is the dark center portion in a tree, and that area is termed the 'juveline core'.
• The growth rings are usually far apart and indicate fast growth coupled with unstable wood.
• Any planks cut from this section of the tree are usually knotty, inclined to twist while drying, and have very little strength.
• On the other hand, if there is a little bark present in the plank, this will indicate that the board has been sawn from the outer section of the tree and will have a higher density.
• These boards will have year rings close together, and the timber will be far more stable.
• The boards will not have a tendency to twist and warp.
• The boards will be much stronger.
• Check that the boards are free of large knots, as these cause a deviation in the direction of the grain and thus severely affect the strength of the wood. (To prevent knots developing, the trees are pruned to a height of about 6 metres, thus disposing of their branches every eight years or so).
• Ensure that the wood is dry (otherwise the wood can shrink up to 4%).
• Avoid heavily infiltrated resin as this could cause coating problems later.
• Discolouration is not all that critical unless rot has set in (blueing does not affect strength as it is only the cell sap that is attacked by fungus, and not the cell walls).
• Bear in mind that in general, timber in the original form is about 5 times the strength of sawn timber, and laminated timber has the advantage of being twice as strong as sawn timber, very much more stable and can be produced up to 15 metres in length and about a max of 1,2 metres deep, by 140mm thick, if required. (Constant moisture content and defects such as knots are minimised and spread throughout the beam).
• Lastly, ensure that the timber is treated, preferably with CCA (green colour) or TBTN in the case of laminated beams, and again check for the familiar SABS markings.

By Lewis Silberbauer LCS Timber Solutions