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Treated wood is typically used in applications where it may be exposed to moisture for considerable periods so the fasteners and connectors must also be resistant to these conditions. In addition, most wood preservatives designed for exterior use contain copper that may react with the metals used to fabricate fasteners and connectors; therefore, it is important to use the right type of fastener and/or connectors. Where treated wood is used in dry environments to prevent damage by wood-destroying insects, including termites, corrosion is of less concern. Users and specifiers should also be aware that corrosive industrial, or salt air, environments may also require the use of appropriate corrosion resistant metals.
Connectors used for ACQ or CA treated wood should either be manufactured from steel galvanized in accordance with ASTM A653, G185 designation, or be galvanized after manufacture in accordance with ASTM A123. Stainless steel connectors (type 304 or 316) are recommended for maximum service life or severe applications. For borate treated wood used inside buildings, the same connectors can be used as for untreated wood.
Fasteners for ACQ or CA treated wood should be galvanized in accordance with ASTM A153. Stainless steel can still be used for maximum service life or severe applications where appropriate, copper fasteners may also be used. Fasteners used in combination with metal connectors must be the same type of metal to avoid galvanic corrosion caused by dissimilar metals. For example stainless steel fasteners should not be used in combination with galvanized connectors. For borate treated wood used inside buildings, the same fasteners can be used as for untreated wood.
Flashing used in contact with treated wood must be compatible with the treated wood and last long enough to be suitable for the intended application. To avoid galvanic corrosion, flashing must also be of the same type of metal as the fasteners that penetrate it Copper and stainless steel are the most durable metals for flashing. Galvanized steel, in accordance with ASTM A653, G185 designation, is also suitable for use as flashing.
There may be additional products such as polymer or ceramic coatings, or vinyl or plastic flashings that are suitable for use with treated wood products. Consult the individual fastener, connector or flashing manufacturer for recommendations for use of their products with treated wood.