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Frequently Asked Questions

General

Can structural glued laminated timber (glulam) be used outdoors?

Glulam timbers will perform similarly to sawn lumber of the same species when used outdoors. For unprotected outdoor exposure the wood used must be heartwood of a naturally durable species or pressure-treated with an approved preservative to insure durability. The International Building Code, Section 2304.11.3 states, The portions of glued-laminated timbers that form the structural supports of a building or other structure and are exposed to weather and not fully protected from moisture by a roof, eave or similar covering shall be pressure treated with preservative or be manufactured from naturally durable or preservative-treated wood. AITC Standard 109-2007 explains preservative treatment options for glulam.

Glulam does not require preservative treatment where it is protected from exposure to rain and snow. The humidity in the air is not generally sufficient to raise the moisture content of the wood to a level that will support decay. If the wood is kept dry, it will not decay. A well detailed roof with facsia or flashing to protect the beam ends is usually sufficient protection for a timber beam. As a rule of thumb, wood should be kept above a plane drawn from the lowest point of the roof or fascia toward the structure at a slope of one vertical unit for every two horizontal units or be pressure-treated or naturally durable. Detailing recommendations and related information are contained in AITC Technical Notes 12 and 13 and AITC Standard 104-2003.

Adhesives used in structural glued laminated timber (glulam) are engineered to be as strong and durable as the wood substrates which they bond. They are subject to stringent manufacturing requirements and rigorous qualification testing prior to acceptance for use. Additionally, tests for strength and durability are performed in the laminating plant on a daily basis. These measures result in an adhesive bond with strength and durability comparable to the wood itself.

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