Facts About Timber
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Published by TOP4 Team
Timber is a naturally occurring building material, either harvested from natural forests or from plantations. It is not a uniform material, showing the faults, variations and quirks of mother nature. It is valued as a structural material and is also used for decorative purposes.
Structurally, timber must be of a suitable durability and strength for the job in hand. There are many publications which classify timber according to its durability and suggest where species of timber are tested for strength.
Colour changes in timber
Timber will change colour if subjected to light. The pigments darken — a natural phenomenon. A common sight in homes with timber-panelled walls is patches of lighter-coloured timber under paintings and posters. What can be done to even out the colour of the panelling becomes a problem.
The timber walls have normally been oiled, so staining may be difficult to do. Even if staining were possible, it would be difficult to blend in the stain.
Time is effective in evening out the patchiness, but this could take some years, depending on how pronounced the difference is. A reasonably heavy sanding can restore the surface to its original colour. This needs to be followed by resealing to match other woodwork in the room. With most timber profiles such as shiplap, this will be a tedious and difficult task.
Resurfacing WRC after weathering
In some people’s eyes there is nothing more heartbreaking than installing beautiful new Western Red Cedar (WRC) around the house, only to find that the timber soon turns grey or black.
All timber will go grey with age and if coated with a clear finish this will appear to be black. Traditionally, a highly pigmented oil stain was considered the answer, even though some of the timber grain was covered.
There is a relatively new product on the market, called Aquatrol. It will not stop the greying process, but can be periodically used to bring the cedar back to a colour close to its original.
Shrinkage of timber
All tradespeople working in timber know that the material changes shape. Firstly, after the timber is cut, it undergoes considerable change in volume. This varies between species and between directions within the timber itself.
During the seasoning period of timber it reduces its moisture content from 100 per cent to 12 per cent or thereabouts. In many cases, the internal stresses of the timber cause bowing cupping and warping.
If you are using ‘green’ timber, especially hardwood, bear in mind that considerable shape changes may occur. All fixings must be solid to hold the timber in place and, if the timbers are deep, they should be blocked to stop twisting and warping.
Secondly, as humidity levels in the environment change, timber may absorb or lose water, resulting in swelling or shrinkage. This is seen in doors that will not shut one day, and will the next. Over-reaction to this problem may leave doors or other close-fitting wooden items with unacceptable gaps, resulting in draughts.
The key to successful timber repairs is that, when timber needs to be replaced with a material that is of a similar moisture content. It is no good replacing a 60-year-old beare with a piece of hardwood that was cut and sawn last week. Use seasoned timber — the second-hand market is often a good source.