Light Framing Code Revision

For the sake of completeness, it is worth while having a qualitative peek at the forestry economics picture which may have led us to the present declining structural properties. Modern forest management aims to maximise the value of the forest over the rotation cycle. It does this by growing trees fast so that the initial investment in land, planting and tending is realised early thus avoiding the compounding interest problem.Few fat trees are cheaper to saw, for a given wood volume, than many skinny trees, so that trees are spaced widely by thinning to encourage diameter growth. Pruning of the first 6 metre log ensures that valuable clear wood is produced. Framing timber does not command a high enough price to justify sawing from the clear wood of the bottom log, so it comes from the upper logs and the knotty core of the bottom log. Radiata pine increases in density and strength properties as you move out from the pith so that beyond about 10 rings from the pith, the older wood is of good quality. Upper logs of fast grown trees have much less of this good quality timber than the lower logs of slow grown trees. As well as this, the branches of the upper logs of widely spaced trees are larger, leading to larger knots. All these factors combine to reduce the quality of framing timber.However, it may well be that the economics are still favourable even if the price of framing timber reduces because of the small increase in the quantities needed to do a particular job. The loss in value of the framing timber is probably more than compensated for by the high value of the pruned butt log.The real killer for timber framing in building would not be a possible decrease in strength properties, but rather a large increase in the amount of distortion, causing builders to switch to distortion free materials such as steel framing. However, the timber industry have this covered through the production of kiln dried framing which has now captured about half of the framing market