Since time immemorial, wood or timber has remained an essential natural resource for mankind. It is a widely used material in woodworking and construction because of its natural beauty, versatility and strength. From framing a building to forming beautiful furniture, timber fulfils both structural and decorative roles in our daily lives.
However, like any other natural material, timber is susceptible to numerous defects that might compromise its appearance, quality and durability. The cause of occurrence of these defects is not one. It might be due to natural causes, improper seasoning or poor handling. The defects potentially weaken its structural integrity, thereby diminishing its strength and aesthetic value.
Whether you are a builder, carpenter or homeowner wanting to maintain your project’s longevity and visual appeal, you must understand the types of wood defects. This blog provides an in-depth understanding of the various defects occurring in timber and the best ways to detect them. It further focuses on offering prevention and treatment strategies, ensuring that timber remains reliable and durable for construction and carpentry.
Types of Defects in Wood
We get timber from trees, which we convert into the required form for usage. Before reaching the final stage of usage, the timber needs to cross several critical stages, including growing without defects, being cut at the right time, seasoning, conversion and usage. Despite these, your timber might experience various defects at various stages due to natural forces, insects, fungi, and during seasoning and conversion.
Naturally Caused Timber Defects
- Wind cracks
Often wood is exposed to strong winds, causing it to shrink. This creates cracks on the outer surface, leaving the wood vulnerable.
- Knots
Knots are the most common defects in wood caused naturally. When a tree grows taller, the lower branches or those close to the ground die. However, the bases of those branches remain in the tree, creating imperfections called knots. Knots are of two types- dead knots and live knots. Often, some branches of trees experience damage. When these dry and fall off, they leave behind some remnants, often referred to as dead knots. After some time, they loosen and fall off. The live knots, on the other hand, are sound and firm. Often, live knots are smaller and remain firmly attached to the timber, which is why they do not cause any problems.
However, dead knots decrease the strength of the wood and cause serious defects when the load falls perpendicular to the grains, lowering its value for structural use.
- Twists
Often, younger trees get exposed to high-speed winds. In such a scenario, the fibres get twisted in the opposite direction. The timber obtained from these trees is unsuitable for sawing. However, you can use them to make polls and posts.
- Shakes
Shakes refer to the timber defects occurring around a tree’s annual ring or growth ring. Simply put, the cracks and splits forming in the wood are called shakes. Depending on the depth and use, you might not experience it as a structural problem. However, it can be an aesthetic problem, as shakes are undesirable when you need to focus on appearance. One can classify shakes into three categories- star shakes, cup or ring shakes, and heart shakes.
- Star Shakes: These shakes propagate from the bark towards the sapwood. Sometimes, you will find them growing even towards the heartwood. If you notice, you will see that the cracks are wider on the outer edge and get narrower towards the middle. When trees get exposed to extreme heat or frosting during their growth, it causes temperature differences, which further cause shrinkages and lead to cracks.
- Cup or Ring Shakes: These shakes follow the annual growth ring of the tree. Exposure to excessive frost action is the primary reason behind these shakes. You can separate the growth ring partially or completely. When the crack separates the annual ring completely, it is called a ring shake, while partial separation is caused by cup shakes. Therefore, you can say that all ring shakes are cup shakes, but not all cup shakes are ring shakes.
- Heart Shakes: Unlike star shakes, heart shakes propagate from the pit to the sapwood along the lines of the medullary rays. These cracks appear when the interior or the central part of the timber shrinks.
- Upsets
Upsets are crushed or compressed wood fibres. The primary reasons for these defects include improper felling of trees and exposure of young trees to heavy winds.
- Rind Galls
Have you ever noticed an abnormal growth in a tree bark? If yes, those are rind galls. When cutting the branches, the tree cutters often make mistakes, causing abnormal growth. Wood from this portion of the tree lacks strength, preventing experts from giving desirable structure to the timber.
Defects in Timber Caused Due to Insect Attack
Often insects like termites, beetles and marine borers infect wood. These insects feed on the wood, creating holes and weakening the strength of the wood.
If your wood experiences a beetle attack, all sapwoods will have holes. The beetles lay their eggs in the wood, and the larvae feed on it. They make tunnels through the sapwood, creating wood dust.
Termites live in colonies and are known for eating the wood faster and creating tunnels through it. However, few varieties of wood can withstand termite attacks.
As the name suggests, marine borers live in saltwater. They attack wood and make tunnels through them to take refuge or shelter. These insects attack all types of wood.
Defects in Timber Caused due to Fungi
- Stain: Fungi mostly feed on sapwood, which is the outer living part of a tree from where the stored food, water and minerals are transported to the leaves. The sapwood comprises a phloem and xylem that move water, carbohydrates and other essential nutrients throughout the tree. During an infestation, fungi feed on this part of the timber, causing a stain. Although the stain does not affect the wood, it leaves a colour, making it aesthetically unpleasant. Since the heartwood does not store food, it remains free from stains.
- Decay: Some fungi infest wood and destroy or eat it. They break the cell structure of the sapwood and heartwood.
Defects in Timber Caused Due to Improper Seasoning
Often, the seasoning of wood becomes faulty, resulting in serious defects in the timber. During this process, the exterior or the surface layer dries before the interior layers and the difference in shrinkage creates stress. The experts create minimum stress and confront the shrinkage if the seasoning process is perfect. Faulty or improper seasoning causes a few defects. These include:
- Check: It’s a kind of crack that separates the fibre without extending from one end to another.
- Honeycomb: The drying process develops stress in the heartwood, creating cracks resembling a honeycomb’s structure.
- Split: These are similar to checks but extend from one end to another.
- Bow: It refers to the curvature formed in the direction of the length of the timber.
- Cup: Have you ever noticed a curved shape forming in the opposite direction of the wood? These are cups.
Defects in Timber Caused Due to Improper Conversion
Miscut: Often, experts make mistakes while sawing and cutting wood, causing defects. The primary reason behind the defect is the lack of experience in sawing and carelessness.
Boxed Heart: When a woodworker saws timber in a way where its pith or the heart falls entirely within the surface through the length of the wood, the timber experiences a boxed heart defect.
Machine Burnt: Experts saw the timber through machines. The machine defect occurs when a machine gets overheated during cutting or sawing the timber.
Machine Notches: During cutting or sawing of timber, inexperienced professionals fail to hold and pull the timber correctly, causing chips or torn mark defects.
How to Check Defects in Timber?
Whether you are using wood for crafting furniture or in your construction project, you must maintain its structural integrity and aesthetic quality. For this, you must effectively detect the various timber defects, as they can significantly affect the durability and performance of timber. Enlisted are the two ways you can adopt to check the timber for any defects.
Visual Inspection
It’s one of the oldest and easiest methods for detecting the presence of any defects in the timber. A thorough inspection of the wood surface will reveal common issues, including knots, warps, cracks and damage caused by insects. You must also look for signs of discolouration, decay, soft spots and fungal growth, as they indicate rot. Have you ever noticed the presence of small holes, tunnels and wood dust on your timber? These are clear signs of insect manifestation. The cracks, splits and warps are signs of improper seasoning and external stress, which compromise the strength of the timber. Ensure that your timber undergoes regular visual inspection, as it helps identify these surface-level defects before they worsen.
Non-Destructive Testing (NDT)
While you can detect surface defects through visual inspection, identifying internal defects is impossible with bare eyes. You must adopt specialised techniques, termed non-destructive techniques or NDT, such as X-rays, electromagnetic testing and ultrasound. Without damaging the wood, these advanced techniques can detect internal defects, such as structural weaknesses, decay, and void. With NDT, your timber undergoes a comprehensive assessment while preserving its structural integrity. These are beneficial in large-scale construction projects, where maintaining strength, reliability and safe performance are essential.
Best Ways to Prevent Defects in Wood
While preventing natural defects in timber is impossible, woodworkers can prevent the occurrence of defects during the processing. Enlisted are the steps you can take during each step of production.
The Production
Defects can arise as soon as the trees are cut. Therefore, the first few weeks are very crucial. Trees that undergo cutting between April and October can develop defects faster than those that undergo cutting during other months because insects and fungi are more active in these months. You can minimise the defects during this time by following a few guidelines. These include:
- Keep the logs wet or store them underwater. You will notice a reduction in issues like warping, cracking and checking.
- You can use an end coating such as paint, which is effective as it prevents the occurrence of checks. Before applying any end coating on the timber, you can also spray chemicals like insecticide and fungicide. It reduces the chances of insect and fungi infestation. However, you must be careful with these sprays, which can harm people and animals.
- Place your timber in the east-west direction instead of the north-south direction. The east-west direction reduces solar heat.
- Ensure to convert the logs into lumber within a fortnight of cutting them, especially during the summers. When you keep the logs sitting in the ground and under sunlight, the timber has a high potential for developing defects. If you plan to saw them, keep them off the ground in the shade, preferably in the water.
The Storage
After sawing the green logs into the lumber, you must season them. This is another phase when defects are common to occur. However, adopting some best practices can prevent decay. If you are air drying the wood, stack the logs evenly, allowing maximum ventilation and avoiding direct sunlight to prevent the occurrence of warp, rot, and cracks.
If you are using a kiln, ensure that you place the green logs in a climate-controlled space after drying. It will dry quicker without undergoing any defects from changing temperatures and humidity. The woodworkers must stack the processed wood with spacers, which prevents timber defects like bowing, warping and twisting. Ensure to check the moisture of the wood. The continuous checking prevents the usage of wood before it is completely dry, thereby preventing warping.
Purchasing the Lumber
When purchasing lumber, check for defective boards at the store by following a few simple hacks. Thoroughly inspect each board, look for knots, wraps, insect damage, shakes and checks. The easiest way to check for warp presence is to hold one end of the board near your eyes while supporting the other end on the ground. Be sure to look through the length of all four directions of timber. You can check the timber’s moisture content with the help of a pinless moisture metre. A moisture content of 20% and above is green wood and must never be included in projects.
Treating Defects in Timber
To boost the timber’s longevity, structural integrity and aesthetic value, you must address the defects in timber. You can treat common timber defects such as rot, decay, insect infestation and cracks by adopting the following techniques.
Addressing Rot and Decay
Often, timber retains a high level of moisture, resulting in fungi infestation. It makes the timber prone to rot and decay, compromising its durability. First, you must remove the rotten or decayed parts of the timber to prevent their spread to other parts. Then, a coating of wood preservatives must be applied to the timber to prevent future decay. Ensure on-time treatment and proper ventilation of wood, as it helps minimise the chances of recurring rot.
Addressing Insect Infestations
Have you ever noticed insects on wood? These insect infestations can severely damage your wood. Ensure to look for signs of infestation, such as the presence of wood dust, small holes, and weakening of the structure. Apply appropriate insecticides and fungicides for treating insect-infected timber, which can also help prevent future infestations. If you notice any severity, contact a pest control service for complete eradication.
Timber defects can occur at various stages. However, they are most common during a tree’s growing period, seasoning and conversion processes. Whether caused naturally or during processing, the defects negatively affect the quality, strength, aesthetic appeal and longevity of wood. Further, they impact the structural safety and fire protection capacity of the building.
Brick & Bolt, as a leading construction firm, ensures to provide the best quality raw materials for all their projects. We provide complete support from the first day until the final delivery of a construction project. Our world-class service enables real-time tracking, communication, quality checks and regular project updates. With a dedicated team of professionals, Brick & Bolt offers personalised designs, catering to your unique tastes and requirements without compromising with the quality. Contact Brick & Bolt today to build your dream home!