04 Sep 2017

TFT Woodexperts discusses the quality and suitability behind timber materials

With building materials prices ever rising and constructors’ margins being squeezed, the quality and suitability of timber materials for self-build projects has never been more critical, writes Jim Coulson, Director at TFT Woodexperts.


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Ensuring self-build costings run to plan means eliminating problems by ensuring your professionals have sufficient expert knowledge of the materials they are specifying, and by better understanding timber’s properties.

Oak, as a typical example, has historical associations with strength and longevity. The majority of builders and architects should know enough about oak to understand that minor cracks appearing along the length of a beam are part of the natural inclination of oak to ‘check’ a little as it dries. Oak, when sawn, air-dries at the rate of around one year per 2 to 3cm of board thickness; and during this process its sap gradually evaporates and a degree of shrinkage happens. A crack across the grain, however, is a different matter, and it will fundamentally affect the strength of the beam.

Too often, TFT Woodexperts gets called in when things have gone wrong. The grading of timber (or more accurately, lack of grading knowledge) is one of the problems on which we get asked to give an expert opinion. The many commercial timber-producing tree species have different grading rules, depending upon their required appearance, or their structural safety. The significance of these grades cannot be understated for self-builders, both when considering which timber should be used and when installation actually takes place.

Ask your contractor or timber merchant whether their staff have undertaken timber grading training, covering the species you intend to use. This should help you to get the outcomes you desire. At Woodexperts, we teach many companies’ staff: a sound knowledge of what can and can’t be expected in terms of structural performance is vital.

From extensions to new-builds, understanding how wood behaves in given situations avoids costly problems. For example, landscaping timbers used in ground contact should be treated to Use Class 4; preferably with a 15-year desired service life. Plywood uses are even more critical to understand. The glue-bond within the plywood sheets is intended for different uses, internally or externally. Complex projects need much deeper knowledge. We were called on recently to advise on a timber species suitable for joinery for a refurbishment on a Caribbean island. It may look like paradise, but the island has tropical storms, and wood-boring insects abound. We needed to specify the right timber, with properties fit for the purpose. We eventually took the project right through, overseeing the manufacture and installation of the windows and doors.

Wood science, properly applied, helps decision-making on the best species or process for any situation. Ask your timber merchant if their staff have Level 4 Wood Science & Timber Technology qualifications because they’ll be more likely to give you reliable advice. And if in doubt about materials, design or quality, or if you’re trying to track down what’s caused a wood problem and need an expert witness, wood technology consultants are here to help.

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