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Re: Galvanized bolts req'd in PT wood?[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: Re: Galvanized bolts req'd in PT wood?
- From: "Thor Matteson, Structural Engineer" <thor(--nospam--at)yosemite.net>
- Date: Mon, 8 Sep 2008 08:23:50 -0500
First, let's decipher the alphabet soup:CCA is chromated copper arsenate--this is the chemical that was "outlawed" in 2004 (it's actually still available for agricultural uses--I guess the arsenic disappears if a cattle eat it after it leaches out of their feeding trough...)
Some of the new treatments are: ACZA--ammoniacal copper zinc arsenate (hmm, still has arsenic...) CC--copper citrate ACQ--ammoniacal copper quaternary CA--copper azole DOT--disodium octaborate tetrahydrateThe only one that I specify for mudsills is DOT--it is less corrosive than CCA was, and it is non-toxic to humans.
When ACZA first came out, a contractor friend of mine used some wood treated with it to build some stairs. He told me that within six months the hot-dipped-galvanized post caps were turning into piles of gray powder.
Another contractor on an on-line forum reported that ACQ-treated sills had reacted with plain-steel anchor bolts within a matter of months to the point that the bolts had lost about 40 percent of their cross-sectional area.
Reports like this from the real world have led me to specify only DOT for treated wood (where the wood is not exposed to water--the DOT leaches out if exposed to rain or ground water). Otherwise I specify stainless steel for anchor bolts, anchor rods at tie-downs, nails that are driven into or through PT lumber, and any framing anchors.
Some articles I have seen suggest using Vycor or some other membrane to separate PT lumber from framing anchors. While this could work if workers *carefully* isolate metal from wood, you still have the issue of nails driven into the PT lumber. I don't see a way around using stainless steel nails for copper-based treatments.
There's more info at my website: www.shearwalls.com/treated_wood.htmlThis issue concerns me a lot; shear wall panel nailing and mudsill anchors can quietly corrode and we will not find out until a bunch of "new" houses slide off of their foundations in a future earthquake.
Thor Matteson, SE www.shearwalls.com
From: "Jeff Smith" <jeffsmith7(--nospam--at)comcast.net> To: <seaint(--nospam--at)seaint.org> Subject: RE: Galvanized bolts req'd in PT wood? This is a multi-part message in MIME format. ------=_NextPart_000_0010_01C9106E.2F651350 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bitCorrect me if I am wrong, but if you specify Ilevel Strandguard treated sill plates you do not need to use galvanized fasteners or barriers, since theirzinc borate does not increase corrosivity.I have been specifying HDG anchors, washers and plywood sill plate nails at CCA pressure treated sill plates and any thing else that comes into contact. I specify a barrier between holdowns and the treated plate, such as polykentape or Grace Vycor. See http://www.strongtie.com/ftp/bulletins/T-PTBARRIER08.pdf Jeff _____ From: bart(--nospam--at)nbse.com [mailto:bart(--nospam--at)nbse.com] Sent: Saturday, September 06, 2008 6:01 PM To: seaint(--nospam--at)seaint.org Subject: Re: Galvanized bolts req'd in PT wood? Diane, I share your interpretation as well and do not think it applies to anchor bolts as pressure treatment does not usually occur through the entire thickness of the plate. (not to mention the holes are larger than the bolt...technically not indirect contact) However.....when the building dept./and/or inpsectors areadamant, I have told the contractor to wipe the bolts with solvent and paint....it usuallly has done the trick... bart ----- Original Message ----- From: "Gould, Diane" To: seaint(--nospam--at)seaint.org Subject: Galvanized bolts req'd in PT wood? Date: Thu, 4 Sep 2008 15:29:19 -0700 2007 CBC/2006 IBC Section 2304.9.5 states that "fasteners" for PT & fire-retardant wood shall be galvanized, stainless, silicon bronze, orcopper. 2001 CBC/2000 UBC Section 2304.3 also stipulated this requirement. On a wood-frame job currently in construction, we have pressure-treated sill plates and the inspector is saying that galvanized anchor bolts (sill boltsand hold-down bolts) are a "code requirement". I understand the new preservatives can be much more corrosive than the old stuff, but was of the impression that bolts are of a large-enough diameter to not pose a concern. I had thought I read that somewhere but I cannotfind any published code language, commentary, or interpretations to support this position. Also, I started thinking, what about the washer? Is that a"fastener"? It's in contact with the PT wood - does that mean it needs to be galvanized too? I could not find a definition of "fastener" in the CBC/IBC.I've been away from wood design for awhile and am feeling a little rusty, soI'm hoping someone can give me some guidance on this. Thanks in advance, Diane C. Gould, S.E. Senior Structural Engineer DGS-RESD-PSB Design Services Section 707 Third Street, Suite 4-105 West Sacramento, CA 95605 (916) 375-4219 phone (916) 375-4916 fax<mailto:diane.gould(--nospam--at)dgs.ca.gov> diane.gould(--nospam--at)dgs.ca.gov
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