What special features does the wood of the fir tree have as a material?
Abbreviation DIN EN 13556: ABAL
Botanical name: Abies alba, Abies spp., family Pinaceae
Distribution: Central and Southern Europe (Abies alba); temperate climate zones of North America and East Asia (other species)
Trade names: silver fir (DE); silver fir (GB); sapin pectiné (FR); abeto, pinabete (ES)
Species of the genus Abies are widespread in the northern hemisphere, most (37) in a region extending from Asia Minor east to Japan, including Nordmann fir (A. nordmanniana), which plays an important role in the European market as a Christmas tree, and A. spectabilis (Himalayan fir). In North America (19), a number of mainly wood-used species grow, such as A. balsamea (Pacific silver fir), A. grandis (Grand fir), A. lasiocarpa (Sub-alpine fir) and A. procera (Noble fir). Among the few (7) species common in Europe, only the wood of the silver fir (A. alba) is regularly commercially exploited, mainly in southern Germany, Austria and Switzerland. After a period of low utilisation caused by the fir extinction in the 70s and 80s of the last century, the wood of the silver fir is currently experiencing a renaissance, especially in southern Germany, where it is used as planed wood for upmarket interior design. The technical properties of the various fir woods do not differ significantly and lie within the value ranges given below for silver fir.
In the end of the stand, the logs are straight as a candle, extremely solid and knotless with a similarly high timber yield as spruce. In contrast, deforestation occurs in low locations and in open stands. Depending on age and location, tree heights between 25 and 50 m and diameters between 40 and 120 cm are achieved with knot-free shaft lengths of up to 20 m. Occasionally, heights of over 60 m are also achieved with chest height diameters of 150 to 200 cm.
Colour and structure
Sapwood and heartwood are not different in colour. The wood is matt reddish to yellowish white, often with a grey-violet tinge. The growth zones are clearly marked, the transition from early to late wood within a growth ring is gradual. On longitudinal surfaces the dark late wood bands cause conspicuous grain (tangential) or stripes (radial). In contrast to the similar wood of spruce (M 57), the resin channels are missing in fir, which is an advantage when considering volatile components in the wood (VOC) during interior finishing.
Straight grained, light-coloured and resin-free coniferous wood without heartwood colouring, with pronounced growth ring structure.
tensile strength u12-15: 80-95(-120) N/mm²
shear strength u12-15 : 6.2-8.4 N/mm²
The processing of fresh as well as dry wood can be carried out quickly and gently by machine and hand with all tools, it is also easy to split, peel and knife, as long as the number and size of the branches is small. Qualities with particularly wide annual rings tend to have woolly surfaces and unclean holes. The screw and nail strength is still satisfactory. Gluing with commercially available glues as well as the usual surface treatments do not cause any problems.
Shrinkage and swelling values are in the middle range and still give good stamina. Both natural and technical drying proceed rapidly with a generally low tendency to throwing and tearing.
Natural durability (DIN-EN 350-2)
The heartwood of the fir is only slightly resistant to attack by wood-destroying fungi and insects. For outdoor use, further (constructive) protective measures are therefore usually required.
Areas of application
Due to its good workability and relatively good technical properties, the wood of the fir tree can be used in many ways. It is offered as round timber, sawn timber, veneer as well as in the form of glued construction elements (solid structural timber, glulam) and, like spruce, can be used for load-bearing and other structures in industrial, sports facility, hydraulic and bridge construction. In interior finishing, fir wood is versatile and can be used for skeleton constructions, load-bearing walls and ceilings as well as wall and ceiling panelling, built-in furniture and general interior finishing; outdoors for facade panelling, balconies, windows and doors, fences and gates.
The silver fir is known for frequent wet core formation with a moisture content of well over 200%, an accompanying phenomenon within the real core caused by bacteria. This leads to correspondingly longer drying times.
Fir – Technical Properties
Weight fresh800-1 000 kg/m³
Weight air-dry450 kg/m³
Weight dry-dry410 kg/m³
Bulk density air-dry (12-15% u)0.41-0.45-0.52 g/cm³
Compressive strength u12-15(26)35-45(-59) N/mm²
Flexural strength u12-15(62-)70-80(-114) N/mm²
Modulus of elasticity (bending) u12-156 200-10 800-14 500 N/mm²
Hardness (JANKA) ⊥, converted1.8-2.8 kN
Hardness (BRINELL) ⊥ to fiber u12-1513-16 N/mm²
Differential shrinkage (radial)0.08-0.15-0.24
Differential shrinkage (tangential)0.24-0.36-0.49 %
Natural durability (DIN-EN 350-2)Class 4 (low durability)