We’ve all heard the horror stories of timber arriving and only half of it being usable. We thought we’d have a quick look at some of the reasons timber can be defective.
Cupping is literally when tangential-cut boards experience shrinkage due to the growth rings swelling faster at the heart, causing them to bow. Radial-cut boards are therefore a safer bet as their shrinkage will be less noticeable.
Knots are often a good indicator of the quality of the timber. The fewer knots, the higher the grade of timber. Knots are evidence of where trees have started to grow branches that got broken off (branch fail!). Knots only tend to dramatically affect the strength of the timber if they are “dead knots”, or knots that have become loose.
As the cause of cupping mentioned above, shrinkage occurs as timber continues to lose moisture content. The drying process increases timber strength, but continued drying often leads to shrinkage.
Imagine a sagging shelf. Incorrect storage or even the board’s own weight if ill-supported can cause gravity to pull it down in the middle.
Like the fraying ends of cloth, splitting starts at the end grain and carries on through the board.
When enormous pressure builds up under the earth, fault lines are present where the earth’s tectonic plates slip past each other due to huge pressures. In trees, when growing (either non-uniformly, or sometimes due to frost) or seasoned, the release of internal stresses, and subsequent “crack!” result in shakes. Shakes can go all the way through the diameter of a tree, making a lot of its wood hard to use. It’s not always apparent until sawing that this fault exists.
This is by no means a comprehensive list of timber defects, but covers a few of the most common you may come across.
Of course, the more timber you have that can be used, the less wastage there is and the further your money goes. Timber that consistently suffers from any of the above defects delivered time and time again is going to give any company a bad name.
Some merchants will simply ship you out what’s in stock, no matter what state it’s in. Merchants that commonly do this aren’t usually concerned with repeat business and you might find you have a hard time getting things rectified, with staff not wanting to know.
A merchant that prides itself on delivering quality timber will have rigorous quality control procedures and mechanisms in place. These should include the timber merchant company buyers visiting the sawmills that the timber is imported from and hand-selecting the timber that they know their clients will be able to use.
Because this is a time-intensive process, prices may be a little higher from a reputable timber merchant, but you’ll be able to use 99% of the timber you receive, rather than 50-60% in some poor cases, for which you’ll end up paying more in the long run in time and money.