All builders know about treated wood. It’s green; its protected 7. Use Class 4 is the level of treatment required for components in against wood decay and insects; it can be used almost anywhere. This is true. However, whilst wood may look treated, how sure can you be that it will be fit for the use intended? There is a way of making sure. British Standards require that treated wood is given a level of protection that matches its end use. For example, an outdoor deck or fencing component will contain higher levels of preservative than an internal floor or roof joist. BS8417 is the British Standard for treated wood. In this standard, construction timber is grouped into four use classes.


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