As with many other building materials, when you work with Pressure Treated Lumber, standard length fence boards, deck planks, posts or timbers often need precision trimming before they can be fastened* in place.

However, unlike rot-resistant Cedar or dense and durable Hardwoods like Ipe (which require end sealing for different reasons – more on that here), the substrate lumber used for Pressure Treating is not naturally resistant to rot and decay.

suitable lumber

Lumber species used for Pressure Treating such as SPF, Hemlock, Hem-Fir and Douglas Fir, do not possess the same natural resilience as Western Red Cedar, Yellow Cedar or other hardier wood species. Therefore when you trim the end off of a piece store-bought Pressure Treated Lumber, you are exposing wood fibre that is not suitable for exterior application without chemical treatment, to water, fungus and insects that it would otherwise be protected against by the Pressure Treatment.

example of treated wood failure due to not treating end cuts

The 3×12 Pressure Treated Wood Stair Stringers in the picture above (left of image) have decayed causing structural issues with this staircase. The wood itself is only 2 years old, but failure to seal the end cuts has allowed water to penetrate into the wood, which has rotted. Had the end cuts been treated, given the thickness of the lumber used, this structure would be without issue for decades.

simple process

Sealing exposed ends is a very simple process which doesn’t cost much money or time – and once you’ve applied an appropriate End-Treatment, you can rest assured that you’ve done a good job and the wood you’ve invested in isn’t compromised by poor workmanship.

IN-GROUND APPLICATION

Whilst treating or sealing any cut ends is important with any Treated Lumber product, maintaining a sealed end is most important when applicating Pressure Treated lumber in-ground, such as Fence Posts and Landscaping / Retaining Wall. Most End-Treatments are designed for use above-ground only, so if you are doing any trimming, it’s important to keep those cut ends above ground – or in the case of tie-backs on retaining wall, facing out so you can safely use an End-Treatment to re-seal the cut ends.

TREATED LUMBER WARRANTY

Many customers don’t realise that Treated Lumber is actually Warrantied on the performance in exterior applications, provided you follow the best practices for handling and installation. Speaking from experience, it is obvious to manufacturers and suppliers if rotten Treated Lumber has gone that way before it’s expected lifespan, due to a failure to adhere to published application and installation guidelines.

^{* Always use Stainless Steel, Hot-dipped Galvanized or Zemax Fasteners, brackets and connectors when working with Pressure Treated Lumber. Failure to do so will cause fasteners to corrode and break, which can cause injury and in some cases loss of life.}