Timber treatment

[gatehill]

Our next door neighbour is building a significant extension to his house and I have acquired some 50m of 4 x 2 rough sawn timber which were the old rafters in the roof. The wood will be some 60 years old and, almost certainly, not treated with anything special.

I am using this to improve my raised vegetable beds in the garden and I am unsure whether I need to weather-proof with any proprietary wood preservative, given the age of the timber.

Has anyone any suggestions?