Splitting timber- A Cause For Concern?

Understanding the Natural Splitting of Timber

Timber is a versatile and widely used natural resource, valued for its strength, aesthetics, and sustainability. However, one common occurrence that woodworkers, builders, and homeowners encounter is the natural splitting of timber. This phenomenon, while often misunderstood, is a natural part of wood's behavior. Understanding why timber splits and how to manage or minimize it can help in making better choices when using wood in construction, furniture making, and other applications.

Why Does Timber Split Naturally?

Splitting, also known as checking or cracking, occurs due to moisture changes within the wood. Trees absorb water throughout their lifetime, and even after being cut, timber continues to interact with moisture in the environment. When cut its approx. 50% of its weight is water. Free water is held in the capillaries and bound water is held by hydrogen atoms.

The key reasons for splitting include:

1. Moisture Loss and Shrinkage

   • Freshly cut timber contains a high percentage of water, known as the wood’s moisture content. As the wood dries, it shrinks unevenly due to differences in moisture loss between the inner (heart) and outer layers (Pith). This tension leads to cracks or splits.

2. Changes in Humidity In Its Environment

   • When wood dries too quickly, either due to high temperatures, changes in humidity or poor storage conditions, it is more prone to splitting. The outer layers dry faster than the inner core, causing stress that results in cracks. This are most evident perpendicular to the growth rings.

3. Grain Orientation

   • The way timber is cut affects its tendency to split. Wood with straight grain patterns is less likely to crack than those with irregular or cross-grained structures. For structural strength most posts and larger sections are cut from the whole truck so they contain both heart and sap wood. Th heart wood dried slower than the sap wood thus leading to more splits.

4. Knots and Weak Spots

   • Natural imperfections in the wood, such as knots, are prone to splitting as they create points of structural weakness.

How Reduce Timber Splitting

While it is impossible to completely eliminate the natural splitting of timber, there are several ways to minimize its occurrence:

1. Proper Drying Methods

   • Air-drying and kiln-drying should be done gradually to allow for even moisture loss. Controlled drying reduces internal stress that leads to cracking. Most drying techniques remove the water from the sap wood but the majority of water in the heart wood remains. FSP- fibre saturation point is achieved after KD but the the majoiry of that is free water (water held in the capillaries)

2. Sealing End Grain

   • The ends of timber lose moisture faster than the rest of the wood. Applying sealants such as wax or paint can slow down this process.

3. Choosing the Right Type of Wood

   • Some species of wood, such as cedar and teak, are more resistant to splitting due to their natural oils and grain structure. Choosing stable wood species can reduce the chances of splitting. Thermo woods have reduced splitting and more dimensional stability but come with an increased cost compared to standard pressure treated timber.

4. Proper Storage and Handling

   • Keeping wood in a controlled environment with stable humidity and temperature prevents rapid moisture fluctuations, reducing the likelihood of cracks. However once installed you may not be able to control the humidity and climatic conditions

5. Using Wood Stabilizers

   • Applying wood stabilizers, such as oils and resins, can help maintain flexibility and reduce stress within the wood fibers.

When is Splitting Beneficial?

In some cases, timber splitting is not necessarily a defect. In rustic furniture, barn wood, and certain architectural designs, natural cracks add character and uniqueness to the material. Some craftsmen even use splitting intentionally to enhance the aesthetic appeal of a piece. The structural strength is not compromised from naturally occurring splits Many will close up when the timber reaches equilibrium with its environment.

Conclusion

The natural splitting of timber is an inherent characteristic of wood due to moisture fluctuations, the humidity levels in the air around it and internal stresses. While splitting cannot be completely avoided, proper handling, drying, and treatment techniques can reduce its occurrence. By understanding why timber splits and how to manage it, woodworkers, builders, and homeowners can make informed decisions when using this valuable material. Timber is and will always be a natural product. If you feel that the characteristics are not to your liking it may be worth considering alternatives such as composites, plastics and metal. Pressure treated timber and more standard softwood timber for building work is dried faster, or experiences short term drying. Splitting can be more prevalent then in some hardwood species that have been dried in controlled environments over longer periods of time.