Why Is My Timber Splitting?

In its natural growing state, timber contains a lot of moisture. As the timber is milled, processed, and eventually put into its end use, it will dry out and begin to shrink. The shrinkage over time will cause ‘checking’, also referred to as splitting. 

As timber grows, it adds layers in the form of growth rings. This naturally builds tension into the fibre. As the timber dries out, the fibre stress can only be relieved by checking. This isn’t a continuous process; it will only progress until the point that it has lost all the moisture. However, depending on climatic conditions, the timber will continue to absorb and lose moisture. 

A lot of the product that goes into fencing and landscaping applications is cut from the centre of the tree, commonly referred to as a ‘heart-in’ product. Some twisting may occur as the product dries out, in addition to the checking. 

While the checking does occur, the product is still fit-for-purpose for outdoor non-structural applications.  

Steps To Mitigate Checking

  1. Coat surfaces with a water-repellent coating, such as Tanacoat.
  2. Cap the exposed ends of posts with post-caps. If post caps are not used, the exposed ends of posts should be coated with a copper napthenate product, such as EcosealTM.
  3. Coat all cut surfaces with a copper napthenate product, such as EcosealTM.



(water-repellent coating)

Available from most Timber Resellers
Post Caps

Post Caps




(copper napthenate coating)

Available from most timber resellers, Bunnings

Other Tips

  1. For best use, stainless steel fasteners are recommended. Galvanised fasteners are also commonly used, but do not have the longevity of stainless steel fasteners.
  2. Any timber that is cut after treatment should be coated with a copper napthenate product, such as EcosealTM.