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What is H5 treated pine and what is it used for?

Is H5 treated pine right for your next project?

H5 pine is one of the most highly rated types of timber in terms of protection against different types of exposure.

This makes it a top choice for projects where the timber will be in constant contact with soil.

What is H5 pine?

H codes represent different levels of timber preservative treatments. The different levels provide a different level of protection against biological decay.

The codes range from H1 to H6 with each code representing a different required minimum treatment, as displayed in the table below.

Timber Hazard level table | Building & Landscaping Materials
This table showing timber hazard level and treatment types has been reproduced with permission of the NSW Environment Protection Authority.

H5 treated pine is one of the highest durability levels of pine treatment.

This means it’s designed to stand up against severe conditions, like in-ground applications or even occasional contact with fresh water.

H5 timber is treated for protection against very severe decay as well as borers and termites.

A Hazard level classification determines what level of protection timber has against certain exposures.

Uses for H5 treated pine

Treated timber 1 | Building & Landscaping Materials

You can use H5 treated pine for a wide range of purposes including:

  • Retaining walls. H5 treated pine will ensure retaining walls are long-lasting and protected from constant contact with soil and moisture.
  • House stumps. H5-treated pine ensures your home’s foundation is well supported and rot-resistant, although concrete stumps are a more popular choice these days.
  • Piling. H5 treated pine is an ideal choice for piling structures.

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How long will H5 treated pine last in the ground?

Because H5 treated pine is highly resistant to rot and decay, you can expect it to last longer in the ground than most other types of treated pine.

As explained in this article, the estimated typical service life of H5 treated softwood ranges from 9 years to 100 years depending on the shape and diameter of the wood.

Differences between H2 and H5 treated pine

The difference between H2 and H5 treated pine is that H5 offers a lot more protection against exposure.

H2 treated pine can be used for interior, above-ground use only and is resistant to termites but shouldn’t be used for applications where it may get wet or be in contact with the ground (for example, cladding or decking).

H5 treated pine can be used in-ground and outside, and in contact with fresh water. It’s suitable for applications such as posts, sleepers and poles.

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What is the difference between H5 and H6 treated pine?

The difference between H5 and H6 treated pine is that H5 is suitable for use in-ground contact and fresh water contact, while H6 is also protected against “prolonged immersion in sea water”.

As an example, fence posts need to be at least H5 graded to withstand rot from being in the ground, or else they will deteriorate quickly.

You can also use H5 grade timber for garden beds or other projects that involve direct contact with soil.

On the other hand, if your project involves building something that will touch marine water—perhaps you’re constructing a boat dock—then it needs to be built out of timber graded as H6.

So, when choosing the right timber for your project, think about whether your structure will come into contact with soil and freshwater (H5) or marine water (H6) since they are treated differently.

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What does F5 mean in timber?

F5 is a structural classification that describes the strength of timber.

As covered in this guide by QTimber, structural timber is “generally sold as a (stress) graded product. A stress grade is the classification of a timber when used in structural applications.”

It states that ‘F’ grades are a “stress grade traditionally allocated to a timber based on its strength group and a visual or machine stress grading system. Higher F grade numbers are given to higher strength groups.”

The higher the F number, the stronger the timber. F7 timber, for example, is stronger than F5.

FAQ

What does H stand for in treated pine?

“H” stands for hazard class. An H1-H6 hazard rating system determines the level of treatment. The higher the rating, the higher the level of treatment. In other words, H1 is the lowest hazard class (and requires the lowest level of treatment) and H6 is the highest hazard class (and requires the highest level of treatment). The lowest levels are protected only against minor insect attacks while the top levels are protected against rot when placed in soil or water.

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Steve Kropp

Based in Melbourne, Steve's passion is vegetable gardening, and he’s been writing about it for almost 5 years. He also loves all things DIY and is always looking for a new project. When not working on his own garden projects or blogging, Steve enjoys spending time with his family, cooking meals with produce harvested from his garden, and coaching his son’s footy team.

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