Treating their timber with a quality wood preservative extends the life of a timber building. Without prior treatment, timber is susceptible to fungal decay and insect attacks which weaken a structure to the point of disrepair. Most wooden garages and outbuildings are built using pressure treated softwood but what does that mean?
There are three main stages to the timber process – preparation, application and drying. Each stage is overseen by fully trained personnel who ensure processes are carries out in a consistent, safe and effective manner.
Before any wood preservative can be applied, the timber needs to be prepared accordingly. First of all it needs to be de-barked, machined and profiled where required. Next, it must be dried down to a suitable moisture content. This initial drying process is important for allowing the effective application of water-based wood preservative in the next stage. If the wood is still too damp when preservative is applied, the timber will not absorb it properly and the treatment will be ineffective.
The initial drying is achieved by carefully controlled air drying methods. These have to be timed carefully and consistently. If wood drys too fast, it can cause unequal shrinkage in areas across the timber which results in cracks and damage which severely weakens the final product. Once the timber is suitably dry it is strapped into blocks that allow gaps in-between and around the outside of each unit. These gaps are important for the next stage as they allow the free flow of preservative to circulate around the timber in equal measure.
To apply the water-based wood preservative, the newly prepared, dried, timber blocks are loaded into a purposefully designed treatment vessel. This vessel is a large pressured, cylinder containment unit. Firstly, before the preservative is applied, an initial vacuum is held which evacuates air from the cells of the timber. This is important as it creates space for the treatment to absorb into. The vessel is then flooded with the water-based preservative and hydraulic pressure applied to allow its penetration into the cells of the timber.
The level of pressure and preservative strength used during a timber treatment depends on the use and class of timber being treated. Treatments are computer controlled to ensure consistency, from the amount and preservative used, to the pressure applied. Once the timber has been under treatment for it’s required length of time, a final vacuum is applied that extracts excess preservative and recycles it for the next batch of timber.
In the final stage, the vessel is vented and the low pressure inside draws the surface solution deep into the timber interior. The timber block is then wheeled out of the vessel and left to dry. To provide traceability, each batch of timber is labelled with documentation that explains what it is, what it was treated with and how long it was treated for. Once each batch is suitably dry, it is packed, bound and shipped – ready for use in construction.