Galvanized Anchor Bolts in Pressure Treated Sill

[jtwright4216]

Found some pretty old discussions on this topic figured I would bring it back to light. IBC, CBC, OSSC all mention the same exception 2304.10.5.1 (CBC)

Exception: Plain carbon steel fasteners, including nuts and washers, in SBX/DOT and zinc borate preservative-treated wood in an interior, dry environment shall be permitted.

To me exterior walls are technically in a dry environment. Simpson strong tie also elaborates on this answering the question;

"I have preservative treated mudsills. Should I be using stainless steel anchor bolts? What about hot-dip galvanized?

The mudsill is a location that is considered dry in comparison to a deck, for example. For wood that is installed and remains dry, the corrosion potential will be comparatively low. Regarding code issues, section R317.3.1 of the International Residential Code (IRC) addresses fasteners for pressure-, preservative-, and fire-retardant-treated wood; Bolts of ½" and greater do not need to be hot-dip galvanized steel, stainless steel, silicon bronze or copper"

I have always used 5/8" diam anchor bolts which is exempt per the residential code but of course you have to design for either code. Can't really pick and choose which requirements you want to follow.

What are your guys thoughts on this? I think for a typical residential house mudsills are in dry environment, not exposed to weather like a deck and therefore do not need galvanized anchors. However, from reading previous posts that is not seem to be the consensus.

 

[Ron]

It would also depend on the exterior facade. For systems that have a drainage issue such as stucco or brick/stone veneer, more protection is necessary.

 

[JAE]

but of course you have to design for either code. Can't really pick and choose which requirements you want to follow.

If you are a one or two family dwelling - you would have to use the IRC. Otherwise you'd be under the IBC.

Not sure why you think you have to design to both.

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[jtwright4216]

JAE - Not necessarily, the IRC establishes minimum regulations for one- and two-family dwellings and townhouses using prescriptive provisions.

I was saying the opposite, you either have to use one or the other like you said, not both.

 

[JAE]

I don't think I'm following you.
Are you designing a one or two-family residence?

For a particular project you use one or the other not both....unless there is a singular element in the IRC-type project where engineering is required (beyond the IRC prescriptions)...which doesn't appear to be the case for your question.



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[jtwright4216]

Hey JAE - Not trying to confuse. Lets stick with the IBC as the code we are talking about. Which has the below statement. So, would you galvanize the anchor bolts in a mud sill or not??

Exception: Plain carbon steel fasteners, including nuts and washers, in SBX/DOT and zinc borate preservative-treated wood in an interior, dry environment shall be permitted.

 

[JAE]

Well the only thing I guess I could suggest is that there are multiple types of preservative out there and the SBX/DOT and zinc borate preservative-treated wood products may not be as aggressive compared to other types of preservative. Perhaps the code is suggesting that these types are not as aggressive and therefore galvanizing isn't required.

I'm not an expert in the different types (perhaps others here can chime in?).

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[dik]

Some preservative methods are quite corrosive... expecially for PWF type treatments and should only use HDG or stainless fasteners.

Dik

 

[jtwright4216]

I guess unless you specify what type of preservative for the sill and verify it, then you might as well call out for galvanized anchors.

So, majority wise, does everyone pretty much spec out galv. anchors then?

 

[racookpe1978]

It is a sill, exposed to view and on the rest of the structure - even if painted, would you not want a stainless bolt (or galvanized bolt & nuts & washers ) simply so the subsequent rust doesn't bleed through in a very visible location?

 

[msquared48]

JAE:

The IRC is less restrictive than the IBC. You can always use IBC provisions in lieu of the IRC.

I always spec'd the IBC and never had any problems.

Mike McCann, PE, SE (WA)