Summary for pressure treated wood fasteners Discussion
pressure treated wood fasteners are the key issue in this deck question: Rick asked whether galvanized brad nails, countersinking, and caulking would protect nails in a wet Rochester, NY climate. The reply advised that stainless steel would be best, with heavy specially coated fasteners as the next choice, but only if they are specifically rated for pressure treated wood. The answer warned that modern pressure treated lumber contains a high copper concentration that can react strongly with zinc, so ordinary galvanizing may fail unless it is very heavy and meets ASTM A153, and even then service life may be limited. Sealing the nails with caulk was said to help only a little because the wood can still hold enough moisture for corrosion to continue. The practical guidance was to choose the correct corrosion-resistant fasteners rather than trying to hide or seal the nails after installation.
Q. I am building a outdoor deck in Rochester NY, a wet and cold climate for 4 + months of the year. I am using pressure treated lumber and want to use galvanized brad nails with a pneumatic air gun. My thoughts are to counter sink the nails to avoid any nail showing and protect the nails from corrosion. I was thinking to seal in the nail with a protective caulk. Would you advise this or a different course of action. A neighbor said to make sure I use the correct nails to avoid deteriorating nails. I did have a friend suggest gluing the cap on but I do not think this will last.
Please advise the best course of action.
Thanks,
Rick
Rick Speciale
hobbyist – Rochester, New York
July 30, 2008
A. Hi, Rick. Stainless steel would be best. Second best would probably be a heavy special paint (the green fasteners you see) — but don’t use any fastener that does not specifically say it’s okay for pressure treated wood. Pressure treated wood used to be generally compatible with galvanizing, but now a very high concentration of copper is used and this causes a shockingly strong galvanic reaction with zinc, so the galvanizing must be very heavy and in accord with ASTM A153
, and even then I think the life expectancy is very limited. Sealing them with caulk may do only a little good since wood absorbs and retains sufficient moisture for the galvanic reaction to proceed.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
July 31, 2008
A. The new pressure treatment for wood is less tolerant of nails than the previously used and now banned one was. Hardware and big box stores sell nails that are specifically marked for PT wood. Consider paint or similar for your nail heads as the top is where the piston bangs it and it will rust there.
James Watts
– Navarre, Florida
August 1, 2008
Q. I’m a facility manager that is trying to deal with the rigors of all of the new specs and all the new sales speak. Recently I was told that my gas pipes were supported improperly because the wood blocks used to support them would eat the galvanized pipe. I understand about ACQ lumber and galvanized hardware but does that translate to pipes as well? There were other issues I was oversold on so I want to ask about this one in particular. Thank you so much for your website and expertise.
Carl Monteleone
Facility Manager – Roselle, New Jersey
March 20, 2012