Tempo:
Untreated wood supported on a concrete slab or footing (such as the sole plate in interior basement walls or basement columns) must be separated by a moisture barrier or the wood must be treated. Where the bottom of a beam is below ground level, it must be surrounded by an air space to prevent contact with concrete or treated to prevent decay. The space around the beam must be left open to allow air to circulate and must not be filled with insulation, vapour barriers or airtight materials. Where untreated framing members are less than 150 mm (6 in.) above the surface of the ground, the framing must be separated from the supporting base by a moisture barrier.
Preservative Treatment In applications where wood cannot be kept dry, other measures such as the use of preservative-treated wood must be taken to provide reasonable service life. Alkaline copper quaternary (ACQ) and copper azole (CA) are the most common preservatives used for residential wood products and are distinguished by the green colour of the finished product. Borate, another chemical used to treat wood against termites and decay, is usually colourless and results in a much deeper penetration of the chemical into the wood than other methods. However, borate tends to leach out of wood that is exposed to rain, so it is approved only for uses where the wood is protected from direct exposure to moisture. Corrosion-resistant fasteners such as those that are hot-dip galvanized or made of stainless steel should be used with treated
wood. Regular nails or screws should not be used and electric galvanized fasteners should be avoided because the protective coating is too thin for long-term service. If preservative-treated lumber must be cut on the job site, the cut ends should be coated with a brush-on preservative until it is no longer absorbed into the wood. Wear gloves when handling treated wood and a mask when cutting it (as for the cutting of many materials). Treated wood should be discarded in accordance with local regulations and should never be burned.
Termites and Other Insects In some areas, wood is subject to attack by termites, carpenter ants and powder post beetles. The map of known termite locations in Canada indicates that they are present only in a few localized areas in the southernmost parts of British Columbia, Alberta, Saskatchewan, Manitoba and Ontario. In these areas, the clearance between structural wood elements and the ground must be at least 450 mm (18 in.) unless the wood is treated with a chemical that is toxic to termites (for example, ACQ and CA). In addition, foundation walls must extend at least 150 mm (6 in.) above the ground. Structural supports must be visible for inspection and the detection of mud tubes that termites build to travel to a food source. Where the foundations are insulated or otherwise constructed in a way that could conceal termite activity, a metal or plastic barrier must be installed through the insulation above finished ground level to control termite passage.
Preservative Treatment In applications where wood cannot be kept dry, other measures such as the use of preservative-treated wood must be taken to provide reasonable service life. Alkaline copper quaternary (ACQ) and copper azole (CA) are the most common preservatives used for residential wood products and are distinguished by the green colour of the finished product. Borate, another chemical used to treat wood against termites and decay, is usually colourless and results in a much deeper penetration of the chemical into the wood than other methods. However, borate tends to leach out of wood that is exposed to rain, so it is approved only for uses where the wood is protected from direct exposure to moisture. Corrosion-resistant fasteners such as those that are hot-dip galvanized or made of stainless steel should be used with treated
wood. Regular nails or screws should not be used and electric galvanized fasteners should be avoided because the protective coating is too thin for long-term service. If preservative-treated lumber must be cut on the job site, the cut ends should be coated with a brush-on preservative until it is no longer absorbed into the wood. Wear gloves when handling treated wood and a mask when cutting it (as for the cutting of many materials). Treated wood should be discarded in accordance with local regulations and should never be burned.
Termites and Other Insects In some areas, wood is subject to attack by termites, carpenter ants and powder post beetles. The map of known termite locations in Canada indicates that they are present only in a few localized areas in the southernmost parts of British Columbia, Alberta, Saskatchewan, Manitoba and Ontario. In these areas, the clearance between structural wood elements and the ground must be at least 450 mm (18 in.) unless the wood is treated with a chemical that is toxic to termites (for example, ACQ and CA). In addition, foundation walls must extend at least 150 mm (6 in.) above the ground. Structural supports must be visible for inspection and the detection of mud tubes that termites build to travel to a food source. Where the foundations are insulated or otherwise constructed in a way that could conceal termite activity, a metal or plastic barrier must be installed through the insulation above finished ground level to control termite passage.
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