What happens when
timber treatment goes wrong.

A construction company had their structural timber vacuum pressure impregnated by another provider. Within a relatively short period, the timber showed signs of pest contamination — evidence that the treatment had not been carried out correctly. The preservative had not penetrated to the wood core, leaving the timber unprotected despite having been treated and paid for.

Proper VPI requires a sustained vacuum to evacuate air from wood cells, followed by preservative forced in at high pressure — typically 10 bar (145 PSI) — and held for several hours. If either the vacuum stage or the pressure stage is cut short, the preservative saturates the surface only. The core remains untreated. This is difficult to detect visually, which is why substandard treatment often isn't discovered until pests establish themselves.

St. Xavier Timber assessed the contaminated timber and carried out a full re-treatment: a complete VPI cycle using 5% Boron Borax at 10 bar, followed by kiln drying to stabilise moisture content. The timber was returned to the client with our standard warranty against pest contamination.

A construction company purchased timber that was represented by the supplier as kiln-dried and ready for use. Within a few weeks of installation, the timber began to warp and crack visibly — behaviour consistent with timber that has lost moisture rapidly after installation in a drier environment.

When the timber arrived at St. Xavier Timber, we measured the moisture content. It was above 56%. Properly kiln-dried structural timber should be at 12–15% moisture content. At 56%, this timber was closer to freshly cut green wood than to dried stock. The rapid moisture loss after installation — as the wood tried to equalise with the surrounding environment — was the direct cause of the warping and cracking.

We ran the timber through a full kiln drying cycle, taking it from above 56% moisture content down to 15%. The drying schedule was calibrated for the species and thickness to prevent stress cracking during the drying process itself. Moisture was verified at multiple points across the load before release.