All About Defects in Timber

Buco 31 Oct 2020

Timber Defects

When working with timber, you have to know what to look for to avoid buying an inferior product. What you have to consider first is that wood is a natural product, and any natural product can have some imperfections and vulnerabilities. It`s important to distinguish and be able to identify defects in timber because weaknesses in the wood you use will lead to or result in an undesirable or even unsafe project. Not all defects in timber come across as weaknesses. Some add to the character or even the strength of the wood.

Before it reaches you, timber goes through many stages that can each have an impact on the quality. Let's get down to the root of what to look for in timber defects. To understand the habitat in which some of these defects form, we have to start with:

HOW DOES TIMBER MAKE IT FROM THE FOREST TO YOUR LOCAL STORE?

Let`s take a look at the process overview from the time timber is de-rooted from the ground to when you see it in the store.

Felling the trees: Trees are mostly cut down in Winter when the wood tends to be dryer.
Storage / Transportation: The cut logs of timber are stored and then shipped to the site where they will be cut and seasoned.
Conversion process: This is where the logs of timber get cut and sanded into planks and pieces, known as PAR. PAR stands for "Planed All-Round"; this means the wood gets smoothed on all sides during the process.
Seasoning: The seasoning process occurs in a few ways, but its main aim is to remove the excess water trapped within the wood. Sometimes wood is stored outside for a while to acclimatise to the local conditions. Sometimes it is brought inside to acclimatise to interior conditions.
Shipped to your store: Once the wood has been processed and seasoned, it is sent to us, ready for you to collect for your next project.

Another factor that produces various qualities within the wood is due to how it gets cut during the conversion process.

HOW IS TIMBER CUT?

PLAIN SAW
TRUE QUARTER SAW
BACK SAW
QUARTER & RIFT SAW

DEFECTS DURING THE CUTTING PROCESS:

More than just the type of cuts made, defects can also occur because of the conditions and method used while cutting down the tree, as well as the weather conditions of the tree`s natural habitat.

Twists occur when lumber rotates in opposite directions at the ends of the board, warping slightly. Sometimes this happens because cutting of trees occurred in very windy areas. It can also be because of moisture absorption during the conversion and seasoning process.

DEFECTS DURING IN THE TIMBER CONVERSION PROCESS:

Machine Burnt: This is when the wood has a blackened appearance and is hard and dull. It occurs during the manufacturing process when it gets burnt by a part of the machine.
Imperfect Grain: Poor quality production planning or miscalculation can sometimes lead to a mismatch in the grain alignment, which creates a significantly weaker wood.
Boxed Heart: This occurred when the timber that got cut ran along the centre of the tree. So, it contains the "heart" of the tree all along with the board. Beams like these will quickly start to crack and twist and land up being purely decorative or entirely useless for construction.
Wane: Sometimes the board was cut, and a piece of the original outer tree rim remains behind, causing one of the edges of the board to have a rounded, imperfect surface.

DEFECTS IN THE TIMBER SEASONING PROCESS:

Wood is either Air-dried or Kiln-dried during the seasoning process. Air-dried wood is left outside to acclimatise to the conditions, while Kiln-dried wood is seasoned using a fire. While Kiln-dried wood is guaranteed to carry less moisture in the end, it is also much more expensive, and most woodworkers use Air-dried wood.

But the seasoning process can also cause a range of defects, such as:

Bowing & Cupping: When the timber is curved or warped. Due to the way it got cut or the amount of moisture within the layers of the wood.
Splits & Checks: Structural weaknesses in weaker woods can leave short or even long cracks in the board. They are sometimes forming only once seasoned and dried.
Honey Combing: Stress develops in the wood during the drying process, and these cracks appear in the form of a honeycomb texture.

GETTING TO THE ROOT OF THE PROBLEM – THE MAIN NATURAL DEFECTS IN TIMBER:

Sometimes the root of the problem lies in the natural habitat and inherent qualities within the tree itself. Natural defects can occur at random and are sometimes only picked up after the seasoning process.

Some of these natural defects are:

Shakes: These are cracks which occur close to the ring within the log. They can cause an undesirable aesthetic to the timber end product.
Rind Galls: When a branch gets removed, improperly, or it has fallen and broken off messily. The trunk of the tree sometimes swells around the area. The aforementioned causes an irregularly shaped grain with inherent weaknesses.
Chemical Stains: Sometimes, gasses in the atmosphere or chemicals in the soil causes dark discolouration in the wood.
Dead Wood: If a tree has died before being cut down, the wood tends to have a reddish hue, and it becomes a lot more lightweight. Timber cut from deadwood is much weaker.
Coarse Grain Effect: Faster growing trees have a larger gap between the annular rings and the wood obtained from these trees are of significantly lower strength.
Insect Attacks: Trees have natural enemies that live off their wood, bugs such as termites and beetles. Many other insects also eat wood and can cause holes within the wood that significantly weaken the structural integrity.
Fungi: Fungi can affect the wood in two ways. Staining is when fungi cause discolouration on the wood, without affecting its strength. Decay is when fungi eat at the wood and break down the cell structure.

TOP TIMBER PROTIP:

DON`T BUY BLUE STAINED WOOD – Look out for timber that has a blueish tint to it in the light. This blue tint is due to fungal infestation in the wood.

When you see a knot in the wood, that means there used to be a branch sticking out of it when it was still on the tree. Some knots can lend a pleasing aesthetic to wood, but any large knots in the wood are generally seen as defects because they weaken the structural integrity of the wood.

There are two types of knots you can identify in wood:

Dead Knots: These are generally darker in appearance and indicates a place where the branch had naturally fallen off. These knots are known to be less firm.
Live Knots: These knots will have a similar colour to the wood grain, and they will appear because the branch was still attached and cut off during the conversion process. If this knot is smaller than 6mm, it will not be a problem in your project.

Luckily, BUCO has the best quality timber & board – SHOP FOR TIMBER ONLINE.

SHOP NOW

Visit your nearest BUCO store today to get the best quality timber, boards and advice for all your woodworking projects.

Enjoy working with boards & timber? Take a look at the related article