When a building is constructed or renovated, it is possible to use lumber which has been treated to prevent termite infestation. This is typically called pretreated wood or “pressure treated lumber” as the lumber is soaked in a specially formulated preservative and then put under pressure to force the preservative deep into the wood. Pretreated wood is a standard product for most construction where the wood is in areas susceptible to termite and decay.
Pressure treated lumber used in a structure must be “field treated” if cut in the field. That is, if a piece of pressure treated lumber is cut exposing non-treated interior, building codes require that the installer treat the end usually by painting on the product.
Pressure treated lumber must be impervious to decay and insect infestation; however, the guarantee is only for a few years. As the preservative may leach out over the years, the lumber can eventually be essentially the same as untreated wood. Pressure treated lumber is a great material and has much value; however, the homeowner must understand that just because pressure treated or “pretreated” wood was used does not mean that there is permanent protection against insects and decay. Termites can avoid pretreated wood by tunneling over the pretreated wood so that the insects do not contact the treated areas.
While pretreated wood is available in most lumberyards, there are products which contain borates which are less commonly found. Borates are derived from naturally occurring minerals mined in California. Borate pretreated wood is gaining more popularity due to customer preference.
Typically pretreated wood is used as the mudsill or sill plate in termite-prone areas. Also, pretreated wood can be used for joists in close proximity to the soil. Finally, pretreated wood is usually required by code where the wood will contact the soil.