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What are the most recommended types of connectors and fasteners that can be used with ACQ, CA, and SBX treated wood?

Dr Galv A325 Bolts 300

The chromated copper arsenate, type C CCA-C) treatment was the standard for wood preservative for many years but was recently replaced by alternative treatments, such as alkaline copper quaternary (ACQ) and copper azole (CA). In addition to these two new preservatives, sodium borate (SBX) treated lumber is now being used for many interior applications. Treated wood is typically used in applications where it may be exposed to moisture for considerable periods. Fasteners and connectors must also be resistant to these conditions. In addition, most wood preservatives that are designed for exterior applications contain copper that may react with the metals used to protect connectors and fasteners. This makes it very important the right type of connectors and/or fasteners are used.

When treated wood is used in order to prevent damage that may be done by wood-destroying insects and termites in a dry environment, then corrosion is of less concern. Users and specifiers should also be aware that corrosive industrial areas or environments with a high level of salt in the air might also require the use of appropriate corrosion resistant metals. Connectors used for ACQ or CA-treated wood should be manufactured from steel and then hot-dip galvanized for corrosion protection. In addition, stainless steel connectors, types 304 or 316, are also suitable for pressure treated lumber. For borate treated wood, used in interior applications, the same connectors can be used. Fasteners used for ACQ or CA-treated wood should be hot-dip galvanized in accordance with ASTM A153. In addition, stainless steel fasteners are recommended, if appropriate. However, 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.


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Comments

John

Can brass screws be used in pressure treated lumber?, tjx

Alana Fossa (AGA)

Hi John, according to performance studies conducted by the pressure treated wood industry, stainless steel and hot-dip galvanized fasteners are recommended. We only deal in the use and performance of hot-dip galvanized fasteners and do not have the necessary information on performance of brass in pressure treated wood.

Ron Hill Construction

I have an outside deck that was built in 2006 using pressure treated joists/framing. The joist hangers and fasteners have corroded and totally rotted and the decking was screwed down with galvanized screws. The tops of the joists are rotten and the screws have corroded off. Looking for input so this wont happen again.

Alana Fossa (AGA)

Hi Ron, Some fasteners labeled as "galvanized" may not be hot-dipped. They could be electro galvanized or mechanically galvanized which do not have as thick of a coating and have different properties. To distinguish, you may need to closely inspect the labeling. Hot-dip galvanized and stainless are the fasteners approved for use with pressure treated wood.

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