Why Timber Cracks and Splits And What You Can Do About It

When you're working with a natural material like timber, some cracking and splitting is completely normal and often, unavoidable. Yet, many people are caught off guard when their timber decking, fence post, or wooden gates begins to show signs of splitting. 

The good news? It’s rarely a sign of poor quality or failure. In fact, timber cracking is a completely natural process, and with a bit of knowledge and care, you can reduce its impact and maintain a beautiful, long-lasting finish

Why Does Timber Split?

Timber, like all natural materials, responds to changes in the environment — particularly moisture. Wood contains water even after it's been felled and processed, and that water continues to move in and out of the wood fibres depending on its surroundings.

As timber dries out, it shrinks. And when it absorbs moisture, it expands. These natural movements can cause the fibres in the wood to separate slightly, resulting in visible cracks (also known as checks or splits). This is especially common in outdoor timber that faces constant changes in humidity, rain, wind, and sunshine.

Importantly, cracking doesn’t usually compromise the structural integrity of the wood. In most cases, it’s just cosmetic though it can become more severe if the timber is poorly maintained or used in high-stress environments.

How to Help Prevent Timber Splitting

While you can’t eliminate splitting entirely, there are several practical steps you can take to reduce the severity or frequency of it. 

1. Start with Properly Dried Timber 

Kiln-dried timber is always the best option. It’s been dried under controlled conditions, so its internal moisture content is more stable and less prone to sudden movement when exposed to the elements. Air-dried timber can work too, but it tends to be more variable. 

2. Store Your Timber Well 

Before installing timber, store it in a cool, shaded, and well-ventilated area. Avoid direct sunlight, as this can dry the outer surface too quickly and lead to uneven shrinking and stress.

3. Use Quality Timber Sealers and Treatments 

Treating your timber with a protective sealer helps regulate how quickly it absorbs or releases moisture. Think of it as a moisture buffer. It won’t stop the natural movements of timber entirely, but it can slow them down, reducing the risk of sudden, dramatic splits.

Our timber and gates, where specified as treated, are protected with Tanalith® E – a water-based, high-pressure wood preservative that guards against fungal decay, insect attack, and rot. Tanalith® E treated timber has an initial green colour as standard, which, when exposed to the elements, gradually weathers to a warm honey brown. Over time, it will naturally fade to a silver-grey finish, blending beautifully with outdoor surroundings. 

4. Design for Movement 

If you’re building a timber structure, include design features that allow for natural expansion and contraction. This means leaving small expansion gaps between boards, using flexible fixings, and avoiding over-tightening screws or bolts. These little allowances can make a big difference in how the wood performs over time.

Embracing the Nature of Timber

It’s important to remember that timber is not a manmade, uniform product. Its beauty lies in its uniqueness and that includes the occasional knot, crack, or grain variation. These features give your structure character and are part of what makes timber such a timeless and popular building material. 

Cracks and splits may appear, but that doesn’t mean your timber is failing. In fact, most of the time, it’s doing exactly what it’s meant to do: adapting to its environment. 

Ready to get the best out of your timber? 

Whether you're planning a garden project or need advice on the right timber for your build, our team is here to help. Contact us today or explore our full range of timber products to get started with confidence.