What is LOSP H3 treated pine?

LOSP H3 is a description you will see on external timber joinery, including some verandah posts, brackets and balustrade components. The two parts of the label tell you different things. LOSP stands for light organic solvent preservative, the treatment used. H3 describes a hazard class for outdoor, above-ground use. Check the marking and the supplier’s instructions for the particular piece you are buying, especially if it is being used in a structural detail.

Where the timber sits matters

Above ground means the timber is clear of the soil. A painted V1 verandah post above a properly detailed base and a fence post going directly into earth are different applications, even if both are outside. The NSW EPA guide to LOSP-treated timber explains where LOSP is used and why it is unsuitable for in-ground use. Ask the supplier or builder to confirm the right material and treatment if a part will sit against the ground or stay damp.

Some details are easy to overlook on a drawing. Look at the bottom of the posts, the top of a rail and the areas behind brackets where water could collect. A part can sit above the ground and still need good drainage and sensible protection at the fixing points.

Check the finish and cut ends

Ask for the preparation and coating instructions before you start, including what to do with end grain and cuts made during installation. Confirm which faces need to be coated before fixing if you will lose access to them later. Read the coating supplier’s directions and check compatibility with any primer already on the product. Keep a record of the coating used so you know what to use when the finish needs attention.

When you inspect painted exterior joinery, pay particular attention to exposed corners, joints and the areas around screw holes. If the coating starts peeling or the timber is exposed, check the supplier’s maintenance guidance before touching up. A damp patch that keeps coming back is worth looking at more closely with your installer so you can find where the water is getting in.

Choose by the job, then the profile

If you are shopping for decorative timber, look at the listed material for the exact profile. The SQBA square-dressed baluster, EB2 eaves bracket and bullnose verandah rafter serve different purposes. Read the specification for the piece you are ordering and confirm the exposure and finish with us if the project calls for something different. For an outside stair project, compare the LOSP pine stair range and Merbau stair range with your builder before settling on a material.

When you enquire, tell us where the timber will sit, what it needs to match and how you plan to finish it. A photo of the location and the proposed fixing can be more useful than the name of the treatment alone.

Talk to the workshop

Don't hesitate to get in touch with us — we would love to discuss your order. Call 03 9720 7266 or 1300 547 581, or send us the details below.