Every now and then someone asks us to quote on trellis using H3 timber to save a bit of money. The price difference is real, but the difference in how long the panels last is bigger, so we wanted to write down the answer.
What the H rating means
The H rating is the New Zealand standard for how heavily a piece of timber has been treated against rot, fungal decay and borer. The number tells you what conditions it can handle:
- H1.2, inside the house, dry conditions.
- H3, outside, above ground, painted or fully exposed.
- H3.2, same as H3 but with a higher treatment retention, much more resistant to fungal decay.
- H4, in-ground.
- H5, in-ground critical, e.g. retaining walls.
Why we use H3.2 for everything we sell
Trellis sits outside in Bay of Plenty sun, salt, wind and rain. The bottom of the panels gets wet whenever it rains. Even though the timber is not in the ground, the conditions are harsh.
H3 will do the job, but H3.2 holds up significantly longer in the same conditions. It costs a little more per metre of timber, but the panels last visibly longer before they need replacing. Across the life of a fence that pays back many times over.
What it looks like
H3.2 treated radiata pine has a faint green tinge when freshly treated. That fades within a few weeks. You can then leave it to weather to a natural silver-grey, or stain it, or paint it. The treatment does not affect the finish.
Stainless steel fixings, while we are at it
All our trellis is built with stainless steel fixings. Galvanised fixings will rust eventually, especially within 5km of the coast. Stainless costs a bit more up front but you do not get rust streaks running down your panels in five years.
Specific questions about treatment levels for your project? Ring Michelle on 07 578 1459.