THE TECHNICAL
PROPERTIES OF
OAK WOOD
Oak wood is one of the most versatile and valuable woods widely used in the construction and furniture industry. With a long tradition of use, oak wood is known for its exceptional technical properties and aesthetic appeal. This article provides a comprehensive overview of the characteristics of oak wood, including botanical classification, distribution, physical and mechanical properties, and possible applications.
Origin and Distribution
Oak wood comes from the genus Quercus, part of the Fagaceae (beech family). There are around 600 different oak species worldwide, with the most important for the timber industry found in Europe, North America, and East Asia. The pedunculate oak (Quercus robur) and sessile oak (Quercus petraea) are the most widespread in Europe. These white oaks are known for their high resistance to wood-destroying fungi and possess excellent mechanical properties.
The red oak (Quercus rubra), primarily found in North America, has a slightly softer structure and is less resistant to moisture and pests, making it less suitable for outdoor use. However, both oak groups are valued for various applications due to their distinct properties.
Technical data of oak wood
Properties | Value |
Botanical name | Quercus spp., Family of the Fagaceae |
Wood Density air-dry (12-15 % wood moisture content) | 0,65–0,80 g/cm³ |
Weight fresh | 950–1.100 kg/m³ |
Weight air-dry | 770 kg/m³ |
Compressive strength (u12-15) | 42–64 N/mm² |
Bending strength (u12-15) | 60–120 N/mm² |
Modulus of elasticity (Bending, u12-15) | 10.200–15.700 N/mm² |
Hardness (JANKA) | 4,8–9 kN |
Hardness (BRINELL) | 4,8–9 N/mm² |
Radial shrinkage | 2,3–3,1 % |
Tangential shrinkage | 4,0–6,1 % |
Differential radial shrinkage | 0,15–0,22 % |
Differential tangential shrinkage | 0,28–0,36 % |
Natural durability (DIN EN 350-2) | 2 (-4) |
pH value | 3,9 (sour) |
Color and Structure
Oak wood is known for its aesthetic variety. The heartwood typically exhibits a light leather-brown color, while the sapwood can range from light gray to pale pink. These color nuances make oak wood particularly attractive for decorative applications.
The growth rings in oak wood are clearly visible, offering a striking appearance characterized by the formation of large earlywood pores. The wood rays are both narrow and wide, creating prominent mirror-like patterns on radial surfaces. These structural features contribute to the beauty and character of the wood, making it especially sought after in furniture and interior design.
Workability
Oak wood, due to its medium density and uniform structure, is easy to work with. It can be shaped with both hand and machine tools. White oak and red oak can be readily processed into veneer, which is used for high-quality furniture and interior fittings.
Special attention should be given to pre-drilling when using screws and nails, as the wood can split easily if mishandled. The ability to glue oak varies depending on its growth conditions; while slowly grown oak bonds well, fast-grown varieties may present challenges. The choice of adhesive is crucial to avoid discoloration.
Drying and Shrinkage Behavior
Drying oak wood requires care and patience. The wood tends to crack, warp, and discolor if dried too quickly. To preserve its properties, a slow and gentle drying process is necessary.
Oak wood's shrinkage behavior is moderate, making it more stable than many other types of wood. Radial shrinkage ranges from 0.15% to 0.22%, while tangential shrinkage ranges from 0.28% to 0.36%. These properties are crucial when planning applications where dimensional stability is required.
Durability and Natural Resistance
Oak wood has a high natural resistance to wood-destroying fungi, making it a preferred choice for outdoor construction projects. The heartwood of white oak belongs to durability class 2 (-4) according to DIN EN 350-2, meaning it has a lifespan of over 15 years under protected conditions. Red oak is less resistant and should not be used outdoors without protection.
Applications
Oak wood is used in a wide range of applications, including:
- Furniture making: High-quality furniture such as tables, chairs, and cabinets.
- Flooring: Parquet and wood tiles.
- Interior construction: Wall paneling, doors, and window frames.
- Exterior construction: Facades, terraces, and garden furniture (preferably white oak).
- Special applications: Manufacturing of liquid containers like barrels, which are particularly valued in the wine and spirits industry.
Appendix: Relevant DIN Standards for Oak Wood
- DIN EN 13556: Symbols for hardwoods (Oak: QCXE)
- DIN EN 350-2: Natural durability of wood against wood-destroying organisms
- DIN 68100 (2010): Tolerance system for wood processing – Terms, tolerance series, shrinkage and swelling measurements
- DIN EN 1912: Strength classes – Structural timber for load-bearing purposes – Assignment of visual grading classes and wood species
This detailed overview of the properties of oak wood highlights why this material is a preferred choice in many craft and construction projects.
In summary - simply explained
Oak wood offers an excellent combination of aesthetics, stability, and technical performance. With its high density, good workability, and impressive durability, oak wood is not only a popular material for furniture and interior design but also suitable for demanding applications in outdoor areas. The different properties of white oak and red oak make them versatile options for a variety of construction and design projects.