A Detailed Explanation of the Material Properties and Grade Classification of American Douglas Fir

Douglas fir is a relatively common construction timber, enjoying high recognition around the world, especially in North America. Because Douglas fir is very hard and has strong wear resistance, it is particularly suitable for use in supports, bridge components, wooden houses, commercial buildings and other places. Let's take a look below at what the material properties of American Douglas fir are and what grades it can be divided into.

1. What are the material properties of American Douglas fir?

1. Douglas fir has a relatively high specific gravity and a certain nail-holding and fastening ability, and is used relatively often in small commercial buildings, residential construction, industrial buildings and the wooden frame construction of multi-storey buildings. Among the softwood species of North America, Douglas fir has a very high modulus of elasticity; in addition, its fibre stress, horizontal shear, tensile strength parallel to grain, compression perpendicular to grain and compression parallel to grain are all among the better varieties of timber.

2. Douglas fir can accept any type of staining treatment. In particular, transparent coatings, varnishes, clear lacquers, paints or waxes, and even bright or soft-toned coatings can all be stained onto the surface of Douglas fir. Of course, in order to achieve a better surface finish on Douglas fir, the moisture content of the wood must be well controlled, and keeping it between 12 percent and 15 percent is relatively good. Of course, the closer it is to normal humidity, the better.

3. The colour and grain of Douglas fir are both relatively good among timbers; its colour is rose-coloured and its grain is straight. Douglas fir that has been exposed to sunlight will darken in colour. The tough fibres of Douglas fir are not suitable for hand carving or cutting, so it is not used to make handicrafts. Power tools or machine tools can only be chosen to process it in order to make the surface of Douglas fir smooth.

4. The gluing strength of Douglas fir is very high, making it very suitable for making glued laminated beams for different buildings.

5. Douglas fir timber is relatively widely used in daily life; in particular, door frames, window frames, wood mouldings, cabinets and some woodwork products are all relatively easy to process. In addition, Douglas fir timber has very high strength and hardness, and while increasing durability it also has the advantage of a low price, offering outstanding value for money and being very affordable.

2. What grades can Douglas fir be divided into?

Grading Douglas fir is generally only carried out in applications in construction or secondary processing industries. If classified according to foreign grading standards, Douglas fir timber can be divided into the following three types:

First, defect-free and knot-free material is mainly divided into grade two and above clear material, grade three clear material and grade four clear material.

Second, if graded according to material for processing, it can be divided into top-grade processing boards, second top-grade processing boards, grade one and above processing material, and wood moulding material A and B.

If distinguished according to building use, it can be divided into light framing material, light structural framing material, structural joists and boards.