H3 vs H4 Treated Pine: What’s the Difference?

H3 vs H4 Treated Pine: Which Should Be Used for Fencing?

One of the most common questions we receive is:

“What’s the difference between H3 and H4 treated pine?”

Although they look very similar, they’re designed for completely different purposes.

Choosing the correct treatment level is critical to the lifespan of your fence.

What Is H3 Treated Pine?

H3-treated pine is designed for above-ground external applications.

It protects the timber against:

Decay.
Termites.
Fungal attack.

Because H3 timber isn’t designed for constant contact with the ground, it’s commonly used for:

Fence palings.
Fence rails.
Fence capping.
Bracing.
Other above-ground structural components.

What Is H4 Treated Pine?

H4-treated pine is designed specifically for in-ground structural use.

It receives a higher preservative treatment than H3 timber and is intended for applications where the timber remains in constant contact with soil and moisture.

Typical H4 applications include:

Fence posts.
Retaining wall sleepers (where appropriate).
Landscaping.
Structural posts.

Why It Matters

Installing the wrong treatment level in the wrong location can dramatically reduce the life of your fence.

Fence posts experience completely different conditions from fence rails and palings.

They’re buried underground, exposed to constant moisture and subjected to significant structural loads.

That’s why selecting the correct treatment level is so important.

Does Better Timber Mean a Better Fence?

Quality timber is only part of the equation.

Even the best treated pine can fail if:

Posts are installed too shallow.
Drainage is poor.
Inferior concrete is used.
Workmanship is poor.

At Crawfords Fencing, we believe quality materials and quality workmanship go hand in hand.

Can You Paint Treated Pine?

Yes—but not immediately.

Freshly treated timber contains moisture from the treatment process.

Allowing the timber to dry before painting helps improve adhesion and coating performance.

As Director Tyrone Crawford often says:

“Painting new treated timber too early is like putting wet timber inside a plastic bag on a hot day. The moisture has nowhere to escape.”

Our Approach

At Crawfords Fencing we use materials suited to the job they’re performing.

We don’t believe in using one product for every application.

Choosing the correct treatment level is one of the many small decisions that contribute to a fence designed to last for decades.

Need Advice?

Whether you’re building a timber fence, Colorbond fence, retaining wall or integrated retaining wall system, Crawfords Fencing can recommend the right materials for your project.