Properties of softwood

Pine (pinus sylvestris in Latin): Grows across the whole of Sweden. Swedish has several different words for pine. Tallen is the young tree. Furan is the mature tree where the diameter of the heartwood is bigger than half the diameter of the trunk. And then the sawn wood is called furu. 

Strength: Medium-hard. 

Common uses: Wood interiors and furniture, windows, flooring, veneers, construction timber and boat timber.  

Treating pine: Pine goes darker over time. To retain the light colour, pine should be treated with lye. Knots may start to show through a few years after treatment. These should then be specially treated.  

Spruce (Picea abies in Latin): One of Scandinavia's most common trees. The wood is often softer and lighter than pine. Spruce is found in both sawn wood products and pulpwood.  

Strength: Medium hard and elastic. 

Common uses: Construction timber, string instruments, flooring, packaging.  

Treating spruce: Accumulations of resin are more common in spruce than pine. When dyeing, the impression of the resin can be perceived as stronger because the pigments do not penetrate the wood where there is resin

Lodgepole pine: The lodgpole pine originally comes from North America and was introduced to Sweden in the 1920s. Contorta is therefore considered an alien species.

Where it grows: Lodgepole pine may be planted in northern Sweden and down to the districts of Värmland, Närke and northern Uppland. Lodgepole pine may not be planted or sown in mountain forests or closer than one kilometer from a nature reserve or protected area.

Advantages: The big advantage of the lodgepole pine is that it grows almost 40 percent faster than the common pine. This is also good from a climate perspective because it binds carbon dioxide faster. It produces up to 40 percent more wood than native pine and is also more resistant to moose grazing, brittle disease and pests. The tree species is also less grazed by moose.

Disadvantages: Disadvantages of the contorta pine are that it can have crooked trunks and coarser branches than the common pine if it is planted in too fertile soil. It is also more sensitive to wind, snow pressure and vole infestation.

Wood is an anisotropic material, which means that the properties differ in different directions. The basic rule is that wood is stronger with the grain, i.e. following the length of the fibres along the stem. Its strength is considerably lower at right angles, i.e. across the grain. This is the case whether the load is caused by compression or stresses in the wood.    

The strength is also affected by the density of the wood and its moisture content, its temperature and the period under which it is stressed. Some rules of thumb:  

• Drier wood is stronger than wood with more moisture.  
• Colder wood is stronger than warmer wood. 
• The longer wood is placed under stress, the more its strength reduces.  

Wood is a material with good thermal properties. This means wood insulates heat well. Thermal conductivity is greatest in the direction of the fibres, and increases with the moisture level and density.