How to Paint LOSP Treated Pine — and Keep the 25 Year Guarantee

Here is the whole method.

Before you paint: wait 72 hours, and keep it dry

Do not paint for at least 72 hours after delivery. The timber needs that time to acclimatise to the conditions where it will live. Keep it dry and under cover in the meantime — primer applied over damp timber traps the moisture underneath it.

Which primer? Oil-based. This is the one rule that cannot be bent.

Use an oil-based primer. Not acrylic, not water-based.

LOSP stands for Light Organic Solvent-borne Preservative — the preservative is carried into the timber by a solvent rather than by water. An oil-based primer is compatible with those solvents, so it bonds with the treatment and is absorbed into the cell structure of the timber rather than sitting on top of it. Once it is primed properly, the product becomes highly water-resistant. A water-based primer cannot make that bond, and the finish will fail early.

How many coats, and on which faces?

Two thin coats of oil-based primer, on all six sides, before installation.

Both halves of that matter:

• Thin coats. Two thin coats penetrate and cure properly. One heavy coat skins over, stays soft underneath and cracks off later. Allow adequate drying time between them.
• All six sides. Including the ends, the back, and the faces that will be hidden once the product is fixed. Unsealed end grain draws water in like a wick, and end grain is exactly what you cannot reach after installation. This is the single most common reason a product fails early — and it is why priming must happen before it goes up, not after.

A pierced fretwork panel is the hardest thing in the range to prime properly, because the primer has to be worked into every cut. An assembled balustrade panel has to be done before it is fixed between the posts. And a gate needs its top and bottom edges primed before it is hung — those are the edges that fail first.

What about the topcoat?

Once the oil-based primer is on and cured, the topcoat is your choice: acrylic, water-based or oil-based all work. Apply two to three thin coats of your chosen finish.

What maintenance does it need?

Inspect it once a year and touch it up. Specifically:

• Look for wear, cracks, or paint breaking down — check the tops of horizontal surfaces and the bottoms of posts first, since they take the most water.
• Lightly sand back any area where the coating has deteriorated, and recoat it.
• Keep every surface sealed so moisture cannot get in.

An annual look and a small pot of paint is the entire maintenance requirement. Skip it and the coating eventually breaks down, and once water is reaching bare timber the clock is running.

What is not covered?

If the coating is not maintained, the natural weathering that follows — cracking, fading and timber movement — is not covered by the structural or rot and decay warranty.

Separately, and regardless of maintenance: timber is a natural product. In line with the Victorian Building Authority and the Australian Standards, small cracks, shrinkage and movement in timber exposed to the weather are normal and expected. They are a characteristic of the material, not a defect.

Does this apply to everything you sell?

No — it applies to external LOSP H3 treated pine, which is the default for our external range and, used above ground, what the 25 year guarantee covers. Products in Merbau, CCA-treated pine, MDF or clear (untreated) pine are different materials with different requirements, and the 25 year guarantee does not extend to them. If you are unsure what your product is made from, call 03 9720 1996 and we will tell you.