Physical Properties of Wood
Contents |
Introduction
Wood is one of the most versatile and widely used materials in the world. It can be used in anything from wood carving and creating small wooden items, such as chairs and rocking horses, to building timber structures and sheds.
It also has a lot of scientific properties associated with it, and every type of wood that is available can exhibit similar, and also different, properties. As such, it is important to understand how different types of wood can be used, so you can make sure that you don’t use the wrong type of wood in your project.
Types of wood
There are two distinct types of wood:
- Hardwoods come from deciduous trees – trees whose leaves fall each autumn – such as oak, mahogany, beech, and birch.
- Softwoods come from coniferous trees – trees whose cones/needles remain all year round – such as cedar, spruce, fir, cypress, and pine.
Specific gravity
The specific gravity (SG) of a substance, is the ratio between the density of the specific substance and the density of a reference substance provided which occupies the same volume. In most cases, the reference substance is water, as its density, in terms of grams per cubic centimetre, is one.
If moisture content is neglected or minimised, the more rings that a tree has within a given space, the denser it is, meaning its specific gravity is higher. Woods that have a higher specific gravity tend to have more lignin in their cells – this increases the rigidity of the wood and its resistance to rotting – and fewer air spaces, meaning that it can’t intake water easily compared to lower specific gravity woods.
Moisture content
One of the most noticeable properties of wood is that it is a hygroscopic material, meaning that it tends to absorb moisture from the air depending on the humidity of its surroundings. If the humidity is relatively high, then the wood will absorb more moisture.
Moisture content is very important when using wood in building, crafting, and manufacturing as it can affect the strength and stiffness of wood. This is because the presence of water affects the bonds between the fibres, effectively weakening the wood and making it more pliable.
Temperature
It is important to understand the thermal properties that wood exhibits.
Thermal conductivity is the ability of a material to conduct heat. For wood, it can range between 0.01 and 0.2 W m-1 K-1, which is relatively low, considering that for copper, it is over 400. The reason for this is because wood is quite porous. The values have a wide range because thermal conductivity decreases as the density decreases.
Thermal expansion is also relatively low in wood, meaning that it can retain its original structure in hot climates.
In freezing temperatures, the water within the wood can expand, causing the it to crack. However, since it has a low thermal conductivity, it means that, in cold weather, it can retain its warm interior and keep the cold weather out, which is why wood cabins are relatively common in arctic conditions.
--G&S Specialist Timber 09:10, 17 Jan 2017 (BST)
Related articles on Designing Buildings
- 11 things you didn't know about wood.
- A guide to the use of urban timber FB 50.
- Ancient Woodland.
- Birch wood.
- Boardwalk.
- Carpentry.
- Chip carving.
- Confederation of Timber Industries.
- Cross-laminated timber.
- Definition of tree for planning purposes.
- Engineered bamboo.
- European Union Timber Regulation.
- Forest Stewardship Council.
- Janka hardness rating scale.
- Lime wood.
- Padauk wood.
- Pine leaves.
- Plywood.
- Predicting service life of timber structures.
- Programme for the Endorsement of Forest Certification.
- Softwood.
- Timber.
- Timber preservation.
- Timber vs wood.
- Tree preservation order.
- Tree rights.
- Tulipwood.
- Types of timber.
- Veneer.
- Walnut.
- Wrot timber.
- Best Woods for Wood Carving
- The Differences Between Hardwood and Softwood
- The Scientific Properties of Wood
Featured articles and news
Retrofit 25 – What's Stopping Us?
Exhibition Opens at The Building Centre.
Types of work to existing buildings
A simple circular economy wiki breakdown with further links.
A threat to the creativity that makes London special.
How can digital twins boost profitability within construction?
The smart construction dashboard, as-built data and site changes forming an accurate digital twin.
Unlocking surplus public defence land and more to speed up the delivery of housing.
The Planning and Infrastructure Bill
An outline of the bill with a mix of reactions on potential impacts from IHBC, CIEEM, CIC, ACE and EIC.
Farnborough College Unveils its Half-house for Sustainable Construction Training.
Spring Statement 2025 with reactions from industry
Confirming previously announced funding, and welfare changes amid adjusted growth forecast.
Scottish Government responds to Grenfell report
As fund for unsafe cladding assessments is launched.
CLC and BSR process map for HRB approvals
One of the initial outputs of their weekly BSR meetings.
Architects Academy at an insulation manufacturing facility
Programme of technical engagement for aspiring designers.
Building Safety Levy technical consultation response
Details of the planned levy now due in 2026.
Great British Energy install solar on school and NHS sites
200 schools and 200 NHS sites to get solar systems, as first project of the newly formed government initiative.
600 million for 60,000 more skilled construction workers
Announced by Treasury ahead of the Spring Statement.
The restoration of the novelist’s birthplace in Eastwood.
Life Critical Fire Safety External Wall System LCFS EWS
Breaking down what is meant by this now often used term.
PAC report on the Remediation of Dangerous Cladding
Recommendations on workforce, transparency, support, insurance, funding, fraud and mismanagement.
New towns, expanded settlements and housing delivery
Modular inquiry asks if new towns and expanded settlements are an effective means of delivering housing.