Why Surface Treatment Is Not Enough
Timber preservation is often misunderstood. Most people are familiar with surface treatments — paints, varnishes, brush-applied preservatives — and assume that a coat of something on the outside will keep insects and fungi out. It will not. Termites and wood-boring beetles do not attack from the surface inward; they enter through joints, cut ends, and checks in the wood where surface coatings are absent or have failed.
Effective preservation requires the active chemical to be present throughout the cross-section of the wood — not just on the surface. That is what Vacuum Pressure Impregnation achieves.
How the VPI Process Works
VPI is a two-stage process carried out inside a sealed pressure vessel. In the first stage, a vacuum is applied to the timber load. This draws air and moisture out of the wood cells, creating space in the cellular structure for the preservative to enter. In the second stage, the vacuum is released and the chamber is flooded with the preservative solution — Boron Borax — under pressure up to 10 bar (145 PSI). The pressure forces the solution deep into the wood cells throughout the entire cross-section.
After the pressure cycle, the excess solution is removed and the timber is allowed to dry and fix. The boron compounds bond with the wood fibres and become part of the material — they do not wash off, evaporate, or degrade over time under normal indoor or sheltered conditions.
- Stage 1: Vacuum removes air from wood cells
- Stage 2: Boron Borax solution injected at up to 10 bar (145 PSI)
- Full cross-section penetration — not just surface treatment
- Chemical fixes within the wood and does not wash off indoors
- Timber remains workable — can be cut, drilled, and finished after treatment
What Is Boron Borax and Why Is It Used?
Boron Borax (disodium octaborate tetrahydrate) is a water-soluble borate compound that is highly effective against a wide range of wood-destroying organisms — termites, powder post beetles, wood-boring beetles, and fungal decay. It works by disrupting the digestive systems of insects and inhibiting fungal spore germination.
Unlike older timber preservatives based on arsenic, chromium, or creosote, Boron Borax is non-toxic to humans and animals at the concentrations used in timber treatment. It is environmentally inert, heavy-metal free, and is classified as a low-hazard preservative by international regulatory bodies. This makes it safe for use in residential construction, furniture, and indoor joinery.
Boron Borax treated timber is safe for use in homes, schools, and food-handling facilities. It is not suitable for ground contact or continuous water immersion — for those applications, alternative preservatives should be specified.
What the 10-Year Warranty Covers
St. Xavier Timber provides a 10-year warranty against pest contamination on VPI-treated timber. This warranty covers failure caused by termites and wood-boring insects in timber that has been correctly treated to the specified retention level and installed in appropriate conditions (dry, sheltered, above-ground applications).
The warranty is backed by treatment records for every batch — retention level, pressure cycle data, and timber species and dimensions — which we provide as documentation with each order. This documentation can be presented to architects, quantity surveyors, main contractors, or insurers as evidence of compliant treatment.
Applications Best Suited to VPI Treatment
VPI treatment is appropriate for any timber application where long-term pest resistance is required. It is particularly important in Sri Lanka's tropical climate, where termite activity is widespread and building without treated timber significantly shortens the usable life of the structure.
- Roof structures — rafters, purlins, wall plates, and ridge boards
- Floor joists and sub-floor framing
- Door and window frames and surrounding joinery
- Furniture, especially rubberwood which is highly susceptible to borers
- Feature timber in interior design — walls, ceilings, decorative screens
- Warehousing and storage structures
VPI and Kiln Drying: Better Together
VPI treatment works most effectively when the timber has been kiln-dried first. Dry timber has lower initial moisture content, which means the preservative can penetrate more deeply and more evenly during the pressure cycle. Treating green or partially dried timber reduces both the retention level and the uniformity of penetration.
At St. Xavier Timber, we operate both kiln drying and VPI under one roof, which means we can sequence the treatments correctly and carry out both on a single order. Timber that is kiln-dried and VPI-treated leaves our facility dimensionally stable, pest-resistant, and ready for installation.