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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: "Gould, Diane" <Diane.Gould(--nospam--at)dgs.ca.gov>
- Date: Tue, 9 Sep 2008 04:51:40 -0700
Subject: Re: Galvanized bolts req'd in PT wood?
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...)
ACQ--ammoniacal copper quaternary
DOT--disodium octaborate tetrahydrate
The 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.html
This 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
> 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.
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> Correct me if I am wrong, but if you specify Ilevel Strandguard treated
> plates you do not need to use galvanized fasteners or barriers, since
> zinc borate does not increase corrosivity.
> I have been specifying HDG anchors, washers and plywood sill plate nails
> CCA pressure treated sill plates and any thing else that comes into
> I specify a barrier between holdowns and the treated plate, such as
> tape or Grace Vycor. See
> 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?
> 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 in
> direct contact) However.....when the building dept./and/or inpsectors
> adamant, I have told the contractor to wipe the bolts with solvent and
> paint....it usuallly has done the trick...
> ----- 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, or
> copper. 2001 CBC/2000 UBC Section 2304.3 also stipulated this
> On a wood-frame job currently in construction, we have pressure-treated
> plates and the inspector is saying that galvanized anchor bolts (sill
> and 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 cannot
> find any published code language, commentary, or interpretations to
> this position. Also, I started thinking, what about the washer? Is that
> "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
> I've been away from wood design for awhile and am feeling a little rusty,
> I'm hoping someone can give me some guidance on this.
> Thanks in advance,
> Diane C. Gould, S.E.
> Senior Structural Engineer
> 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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