Strength is a vital characteristic of superior construction timber-it´s largely based upon branch diameter or knot size. For bending strength at the level which design requirements are set Douglas-fir shows a higher strength than radiata pine. Builders turn to Douglas-fir first for superior strength and reliability.
Douglas-fir is best known for its tough fibre and dense grain structure. It´s grown with more trees per hectare than pine varieties, producing smaller branches (<~40mm). The branches are also scattered and not produced as a whorl (or ring around the stem of the tree) so knots are generally smaller and scattered giving greater strength.
Douglas-fir does not have the juvenile pith and growth rate issues of pine. It is also grown to a much older age, typically 40 to 50 years old, before being harvested and as a result it has a substantially higher stiffness compared to the common pine species.
Douglas-fir is well known amongst builders for its strength and its use for structural beams. Its reputation for reliability and strength is second to none.