Treated wood in roof assemblies.

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Author Message Brian Payne, AIA Senior Member Username: brian_payne Post Number: 152 Registered: 01-2014 Posted on Tuesday, June 26, 2018 - 04:41 pm:    Due to corrosion issues with the current chemicals used in treated wood, I have been specifying as little treated wood as possible. This isn't that hard considering most of my projects are non-combustible steel/concrete/cmu jobs. Anyone still spec'n treated wood and if so...mind sharing exactly where and why? John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1746 Registered: 03-2002 Posted on Tuesday, June 26, 2018 - 04:52 pm:    The code requires it when in contact with masonry. Switched to naturally resistant species for blocking for roofing systems. In other scenarios where PT was advisable due to frequent contact with water/moisture. When in contact with steel, I specified separation sheets such as self-stick air-water barrier sheets. Spec'd stainless fasteners, too. David G. Axt, CCS, CSI ,SCIP Senior Member Username: david_axt Post Number: 1691 Registered: 03-2002 Posted on Tuesday, June 26, 2018 - 05:23 pm:    Yes there are corrosion issues with fasteners when using treated wood. I typically specify either highly galvanized G180 or stainless steel or epoxy coated fasteners. Here is a good article: http://www.ggashi.com/wordpress/wp-content/uploads/PT-Lumber-Causes-Steel-Corrosion.pdf Simpson Strong-Tie also has a wealth of knowledge on using their connectors with treated wood: https://www.strongtie.com/products/product-use-information David G. Axt, CCS, CSI, SCIP Specifications Consultant Axt Consulting LLC Wayne Yancey Senior Member Username: wayne_yancey Post Number: 875 Registered: 01-2008 Posted on Tuesday, June 26, 2018 - 05:28 pm:    Brian, Mostly FRTW lumber for interior blocking, backing and plywood for terminal backboards. Occasionally for roof parapet blocking for nailing base. Also required for the core (typically MDF) for wood wall paneling in means of egress such as through a lobby. And what John B wrote. Edward J Dueppen, RA, CSI, CCS, LEED AP Senior Member Username: edueppen Post Number: 45 Registered: 08-2013 Posted on Wednesday, June 27, 2018 - 08:45 am:    About a decade ago the main driver for me to drastically reduce the use of pressure treated wood was complaints from roofing contractors. They were so frustrated with the twisting and cupping of treated wood. At that point I re-examined where code required it and reduced it to that. And as the others have indicated, stainless steel or epoxy-coated fasteners and separation sheets are essential.