Heart wood is light reddish brown when dry although quite pink when fresh sawn with contrasting creamy white colouration. There is a strong contrast in colour between early and late growth which gives prominent growth rings resulting in strong grain pattern and figure. British trees are faster growing compared to its American cousin which does alter the colour/density.
British Douglas fir is good for structural work rated BS EN 350 class 3 moderately durable. suitable for Cladding, Fencing, Decking and Flooring.
Slower growing and denser than British Douglas fir American Douglas fir is good for structural work rated BS EN 350 class 3 moderately durability. Cladding, Fencing, Decking and Flooring.
Light brown colour with a hint of red and/or yellow, with darker growth rings and very few knot.
American Douglas Fir is
Durability is the ability of a species to resist decay either naturally or through preservatives. The Class is based on the ability of the heartwood (inner part of the tree) to resist fungal decay. The sapwood (the living outermost portion of the tree)is considered not durable and should not be used for external projects without preservative.
Class 1 to 3 can be left as untreated timber, a natural ageing process will accrue e.g. Larch will turn a grey colour. Class 4 and 5 will need to be treated with preservatives.
For further information see www.greenspec.co.uk/building-design/cladding-durability-quality