It's entirely normal for customers to contact timber suppliers during the Spring and Summer months with concerns about cracks appearing in their timber. This is a common and expected occurrence, especially during periods of hot, dry weather.
Timber is a natural material, cut from real, living trees. As such, it retains many of the characteristics of the tree it came from, including its natural response to changes in temperature and moisture. During warmer, drier weather, timber can lose moisture and shrink slightly—a process known as seasonal checking. This often leads to visible surface cracks or splits, particularly in outdoor posts exposed to direct sunlight and heat.
When it comes to large timber such as 150x150mm posts they often contain the heartwood, which is the denser, stronger part of a tree. The heartwood provides the post with greater strength and durability, making it ideal for heavy-duty use. However, the outer layers of the post, which are the sapwood, are softer and more prone to external factors like moisture changes. This difference in hardness between the heartwood and sapwood often leads to the development of shakes or cracks, particularly as the wood dries out or is exposed to weather. These natural features don't affect the overall strength of the timber but are simply part of the wood's normal characteristic behavior.
It’s important to remember that timber is not a manufactured product—it's a natural material shaped by its environment, both before and after it’s been harvested. Some variation and movement are entirely normal.
In winter, the air tends to be cooler and more humid. Timber absorbs some of that moisture, which makes it swell slightly. As the wood swells, the shakes naturally reduce in size or close up altogether.
If you have any questions about your timber or are unsure whether a crack is cause for concern, don’t hesitate to reach out...