What are the special features of Sitka spruce as a material?
Abbreviation DIN EN 13556: PCST
Botanical name: Picea sitchensis, family of the Pinaceae
Distribution: West coast of North America (Alaska, British Columbia, Northern California, Oregon, Washington)
Trade names: Sitka Spruce, Sitka Spruce, Tideland Spruce, Western Spruce
Of the numerous species of spruce, Sitka, known as Sitka Spruce in the English-speaking world, together with the native spruce (= Picea abies) is one of the most important spruce woods.
Straight and round, thicker at the base, with roots and slightly woody. Diameter usually 0.8 to 1.2 m. Branchless trunks often 15 to 20 m, sometimes up to 30 m long and with a particularly large proportion of knotless wood.
Colour and structure
Sapwood yellowish-white to whitish-grey, 3 to 6 cm wide. Heartwood slightly light brown to pinkish brown, slightly darkening and therefore still distinguishable from the sapwood in contrast to native spruce; planed with a silky sheen. Pores not present. Wood rays very fine, only still visible as small mirrors. Storage cells not perceptible. Sitka, like many coniferous wood species, contains resin channels; however, their number and size is so small that they cannot be seen without a magnifying glass. The strongest influence on the appearance of the wood results from the formation of the annual rings. They consist of a broad, light-coloured early wood and a narrow, brown late wood, sharply set off on one side, which is easily recognisable as a darker grain or striped structure. The width of the annual rings, which mainly depends on the age of the tree, is often less than 4 mm, whereby the early wood, in contrast to the larch among others, always remains wider than the late wood.
Bright, light and usually finely evenly structured coniferous wood.
The wood of Sitka spruce grown in Europe is basically the same in appearance; however, due to its low age, it has a less fine-grained quality and a lower proportion of knot-free wood.
Light and mostly fine-grained softwood with predominantly good strength properties at a relatively low weight; the best qualities include wood with annual ring widths of 1 to 4 mm. The drying process is fast and can be carried out as open-air or technical drying. The visual coil is moderately large and gives satisfactory to good durability. The processing can be carried out easily and cleanly with all hand and machine tools with only little effort. In the case of wood which is more coarse, care must be taken to ensure that the tools are sharp enough to avoid woolly surfaces or dented edges when planing, milling, drilling or chiselling. Sitka is easy to nail, screw and glue.
The resistance to fungal attack is still sufficient for outdoor use due to the low moisture absorption if ground contact and stagnant moisture are avoided (resistance class 4-5 according to EN 350-2).
The dry wood is odourless.
Sitka is a good paint carrier and therefore suitable for all painting methods used in interior design, such as colourless, coloured, transparent or opaque paints, and can also be treated to emphasise the structure by reaction staining or simple colour stains. Mechanical processes, such as firing, can be carried out effectively. For outdoor use in exposed locations, chemical protection against fungal attack must be used (see Properties).
Areas of application
In interior construction as solid wood for wall and ceiling panelling, including sauna rooms as well as for light frame constructions, mouldings and panelling, in musical instrument construction for organs and soundboards. Due to its good bending strength and relatively low weight, it is particularly suitable for ladder struts, sports equipment, boat masts, belts and for the construction of racing boats and gliders. As sliced veneer mainly for laminated parts of particularly light, load-bearing constructions. In the North American countries where Sitka Spruce is produced, large quantities of its wood are also used to make boxes, packing drums and butter churns, as well as for the production of high-quality cellulose.
Since Spruce is basically the English collective name for all spruce woods, the woods of other American spruce species, such as White Spruce (= Picea glauca), Bleck spruce (= P. mariana) and Engelmann Spruce (= P. engelmannif) are also referred to in the trade as Spruce in short form.
Sitka spruce – Technical properties
Weight air-dry480 kg/m³
Weight dry-dry410 kg/m³
Compressive strength u12-15 41 N/mm²
Flexural strength u12-15 71 N/mm²