Introduction to Timber

Thinking of building with timber? If you are new to the world of wood, we have got everything you need to know to make your first project a success. From different types to durability, it is the complete guide to timber from our EcoChoice experts.

Timber Grading

When we talk about timber grading, we are referring to the process of inspecting and categorising timber. After a tree is felled and turned into timber planks, an expert assesses the size, condition and quality of each piece in order to give it a grade. Our team at EcoChoice, as well as other people who are used to working with timber, can then use this grade to learn more about the quality of timber we will be getting.

There are two types of grading: mechanical and appearance (or visual). Let’s take a look at each.

Mechanical Grading

Mechanical grading is used to work out the strength characteristics of timber planks. It is usually carried out by a piece of machinery (as the name suggests) called a strength grading machine. This measures the stiffness and load-bearing capacity of the wood and automatically grades it.

Mechanical grading is particularly important in the construction industry, where the timber will be used in a load-bearing capacity, e.g. for beams or decking. 

Appearance Grading

Appearance grading (or visual grading) is usually done by eye rather than machine, with an expert assessing the timber’s appearance to determine the end use. Factors such as the colour and grain of the wood, as well as knots, are considered, telling us more about the quality of the timber. 

Timber Supply

We source and supply a wide variety of timber species, all of which are from responsibly managed forests. From well-known species, such as Oak and Ekki, to more unique woods, such as Balau and Guariuba, we can supply high-quality timber directly to your construction site. With our expert knowledge of grading, we will ensure the FSC-certified timber you receive is suitable for its end use, and we are happy to help with advice on installation and maintenance.

Timber Defects

As a natural resource it is not unusual for timber to have defects, which is why grading is so important. Defects in timber fall under either quality defects or condition defects.

Quality Defects

Quality defects in timber can affect the end use, with some issues making the wood less durable or aesthetically pleasing. Defects we always look out for include:

• Structural defects – including pitch and bark pockets, knots, pitch wood, compression wood, cross grain, interlocking grain, scars, damage from insects or rot, and watermarks
• Manufacturing defects – including issues when sawing including wane and incorrect measuring
• Deformities – including bowing, cupping, springing and twisting
• Shakes, splits and checks – including ring shakes, heart shakes and seasoning damage

Condition Defects

Defects in condition make the wood less suitable for certain applications and can include:

• Moisture defects – when the moisture content of the wood is not as expected which hinders the seasoning process
• Discoloration – including blue discolouration (an issue caused by fungi) as well as other colour changes which occur when the timber is dried or stored

Timber Defect Keywords

If you are looking into timber defects, or want to get a better understanding of the terminology our experts are using when it comes to your wood, here are some key words and terms which are helpful to know:

• Split – separations or tears in the wood which happen at a cellular level, often caused by temperature changes
• Shake – the separation of timber along its length (usually spotted around the annual growth rings)
• Stain – usually brown or blue discolouration from the natural timber colour in irregular patterns and patches
• Wane – a lack of bark or surface timber at the edges and corners
• Weathering – changes in colour of the surface timber caused by exposure to light and outdoor weather conditions
• Mould – a growth on the surface of the timber caused by rot and humidity

Different Types of Timber

Depending on the end use of your timber, we might recommend different types or species which are better suited to your project requirements. Here is a run-through of the different options available and what they mean.

Hardwoods

Hardwood timber is derived from slow-growing, broad-leafed tree species known as Angiosperms. Though not always, hardwoods tend to be tougher and more durable, making them better suited to a wide range of applications.

Softwoods

Softwoods come from Gymnosperm trees, which are usually faster growing than hardwood tree species. They are often cheaper than hardwoods, making them a popular choice in manufacturing and construction.

Heartwood

Heartwood is the centre area of a timber log and includes the pith.

Sapwood

Sapwood refers to the outer layers of the timber and makes up everything between the heartwood and the rough bark. This area is most susceptible to stain.

Moisture Content of Timber 

Timber absorbs and releases moisture based on the surrounding environment and the conditions in which it is placed. Before installation, therefore, it is crucial that timber is dried to the correct moisture content. This refers to the amount of water contained in the timber, written up as a percentage of the total weight. For dry wood, you should expect a moisture content of around 14%-20%.

Timber Drying

To achieve the right moisture content, timber needs to be dried. Dried timber is more durable and less likely to warp, bend and twist, making it more suitable for construction projects. If you install timber whilst it is still wet, it is likely it will shrink and warp over time as it adjusts to the surrounding humidity, which is not ideal in construction. 

By drying timber, the tension within it is reduced and there is less chance of warping and changing size. It is stronger, too, and will be easier to use with metal fastenings. Dried timber is also less likely to stain and decay, and you will find it a lot easier to maintain over the years. 

Air Drying Timber

Timber can be air dried, which is an eco-friendly solution but does take a fair bit of time and is not easy to monitor. In the air drying process, your timber planks will be stacked with gaps which encourage air flow, allowing the moisture in the wood to evaporate slowly .

Kiln Drying Timber

When you want timber to be dried more quickly and more evenly, it is best to opt for kiln-drying. In this approach, the timber is placed in a hot kiln or de-humidifier and left to dry until the correct moisture content is reached.

The Durability of Timber

It is well-known that timber is a durable building material, making it a popular choice for high-quality constructions. However, not all timber is created equal. To learn more about specific planks, durability classes are used to rate how long the timber is expected to last when in contact with the ground, and tells us more about the suitability for different end-use applications. Let’s take a look at the different classes:

• Perishable – will last less than 5 years
• Non-durable – will last around 5-10 years
• Moderately durable – will last around 10-15 years
• Durable – will last around 15-25 years
• Very durable – will last more than 25 years

These classes are based on stakes which are planted in the ground, so bear in mind that when used in applications such as roof beams, your timber is likely to last longer. Preservative treatments and maintenance can also extend the life of timber, and we recommend looking into options like ThermoWood and OrganoWood for projects which are intended to last longer. 

General Timber Terms

To finish up our introductory guide, let’s take a look at some more timber terms which are useful to know:

Quarter Sawn

Also known as rift-sawn, quarter-sawn timber is cut radially from the log to achieve a straight-grain and vertical edge. 

Rough Sawn

Rough-sawn timber is cut using a saw for a rustic finish which is not smoothed down, unlike planed timber which is. For a project with a more natural, imperfect aesthetic, opt for rough-sawn timber.

Hit or Miss

This refers to timber which will be surfaced or partly surfaced after machining.

Find Sustainable Timber For Your Project

If you have a project which you are intending to build from timber, we can help. Our team at EcoChoice are experts in all things timber related, and can supply a vast range of species and finishes, ensuring you get exactly what you need for the job at hand. To learn more or start an order, get in touch with us today and we will be more than happy to help.

Image: Volodymyr_Shtun /  Shutterstock.com