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Re: Galvanized bolts req'd in PT wood?

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Thanks to everyone for the info and thanks also to Jeff and Thor for the helpful and informative links.  IMO, a strict reading of the code gives you a choice of using galvanized, stainless, silicon bronze, or copper fasteners w/ PT wood and doesn't specify a need for stainless with the more corrosive treatments.  But the table on pg 4 of the Simpson Technical Guide T-PTWOOD08 (this table is also in Simpson's hardware catalog) takes a much more conservative approach, recommending stainless for all but a few conditions.  I am still a bit stunned as I find it difficult believe the SE community at large is currently specifying stainless fasteners to the degree recommended in Simpson's table (which is in line with what Thor mentioned) - yet.  But, as I mentioned, I've been away from wood design for awhile so maybe this is just taking me by surprise and most folks are already on board with this.  Or maybe the next code cycle will include language that incorporates recommendations based on Simpson's and other research. 
 
Thor, what about the washers for the sill plate bolts (or any bolts for that matter)?  Would you use galv washers with borate treated wood, stainless with other treatments?
 
Regards,
 
Diane Gould
diane.gould(--nospam--at)dgs.ca.gov
 
From: "Thor Matteson, Structural Engineer" <thor(--nospam--at)yosemite.net>
To: <seaint(--nospam--at)seaint.org>
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...)
    CC--copper citrate
    ACQ--ammoniacal copper quaternary
    CA--copper azole
    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
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
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>
> Correct 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
> their
> zinc 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
> polyken
> tape 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 in
> direct contact)   However.....when the building dept./and/or inpsectors
> are
> adamant, 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, or
> copper.  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
> bolts
> 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
> 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,
> so
> I'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