Corrosion of Fasteners at Pressure Tr...

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Author Message Nathan Woods, CCCA Senior Member Username: nwoods Post Number: 19 Registered: 08-2005 Posted on Wednesday, September 21, 2005 - 08:19 pm:    I’m just starting to dig into the scary world of corrosion and pressure treated and/or fire treated wood products. Although I’m not clear on why, it seems that most mfr’s of the chemicals used to create pressure treated and fire treated wood have changed their formula’s. As a result, the proper specification of which corrosion resistant fasteners to use has become much more complicated, or so it would seem? After preliminary research (what did we ever do without Google?), it appears that each pressure treated wood vendor or product has it’s own base chemical composition, and a specific fastener material must be used accordingly. How is this managed at the Specification level? How is this managed in the field? If I have a pressure treated 3x mud sill at a fire treated shear wall panel, is the contractor expected to switch nail guns or cartridges when they do their nailing? This sounds rife for problems, failures, and potentially lawsuits. I don’t have any answers at this point. I’m quite sure I have not even thought of all the relevant questions I need to answer. For example, as I’m typing this, it occurs to me that stucco lath, flashing nails, railing bolts, etc…all anchor to treated lumber, particularly on a Type III wood framed building. I’m very curious to hear your collective thoughts on this, and hopefully, some proposed solutions! Regards, Nathan Woods Southern California Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 157 Registered: 05-2003 Posted on Thursday, September 22, 2005 - 12:22 am:    Nathan - Blame the EPA, suggest you catch up on your reading - Strongtie has some good info: http://www.strongtie.com/productuse/PTWoodFAQs.html http://www.strongtie.com/ftp/bulletins/T-PTWOOD05.pdf Bottomline, we no longer specify standard galv fasteners in contact with PT wood, we prefer Stainless steel, if forced to specify galv. we go for the G185 hot-dipped galv. We also no longer specify aluminum flashing in contact with PT Wood, again we specify stainless steel or Kynar painted aluminum. Mitch Miller,AIA ,CSI,CCS Senior Member Username: m2architek Post Number: 58 Registered: 02-2004 Posted on Thursday, September 22, 2005 - 08:47 am:    there was another string here awhile ago when the issue arose. The real scary fact is that the treatments are high in copper content, so the galvanic action with other metals is the issue at stake. I have a power point presentation I did for my chapter and our offices. email me if you wish to see it. Wayne Yancey Senior Member Username: wyancey Post Number: 69 Registered: 05-2005 Posted on Thursday, September 22, 2005 - 11:42 am:    Nathan, Nails: For Borate pressure-preservative treated rough carpentry (dimension lumber and panel products, I specify Type 304 or 316 stainless steel or double hot-dipped STORMGUARD fasteners from Maze Nails. For ACQ or similar pressure-preservative treated rough carpentry: Type 304 or 316 stainless steel. Maze nails are available collated. Contractors like this feature. www.mazenails.com Bolts, flat washers, hex nuts: Same rules as for nails in Borate or ACQ treated product. W.R.Grace has suggested details for separating treated lumber from fasteners that is worth reading. I spec Borate for wood above grade and not directly exposed to weather (such as furring and strapping for rainscreen cladding). I spec ACQ for wood exposed directly to weather. I hope this helps. FYI, my region is the Pacific northwest (Marine climate). Wayne Steven T. Lawrey, AIA, CSI, CCS, CCCA Senior Member Username: lawrey Post Number: 33 Registered: 08-2004 Posted on Friday, September 23, 2005 - 09:56 pm:    To get around fastener coordination I've started specifying untreated Doug Fir with galvanized fasteners for roof blocking. Got this tip from a talk given by Sal Verrastero at one of our chapter meetings. I'm in Philadelphia which has "whimpy" mid-atlantic climate. Thus far I haven't had to deal with wood building super structure, decks, pergolas, etc.