Galvanized Fasteners & Treated Lumber

[bridgebuster]

Is there a problem with using galvanized fasteners with pressure treated Douglas fir/Larch?

I designed an open portico structure - it's part of a streetscape. The portico consists of a pitched roof with timber rafters, and timber beams along the eaves. There are four concrete/stone columns along each side. The ridgebeam is a galvanized tube, since it had to span 40' without interior supports. The rafter collar ties are galvanized steel straps.

At the last minute the architect says no galvanized fasteners. it will stain the wood. If the fasteners are going to stain the wood one would think the galvanized members will do the same to it. I'm looking for opinions before I start revising the drawings.

Thanks and Happy Thanksgiving.

 

[SlideRuleEra]

bridgebuster - Hot-dip galvanized (or stainless steel) fasteners are recommended for use with treated lumber. This applies to all of current preservation processes. The concern is about the preservation chemicals, the wood species is not an issue. Note that galvanizing, other than hot-dip, is not recommended.

Simpson has as good a summary of this entire question as I have seen anywhere:

http://www.strongtie.com/productuse/ptwoodfaqs.html#metals

Happy Thanksgiving to you, too!

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[jayrod12]

IF they're worried about staining it will be worse without galvanized or stainless steel fasteners. The preservatives used to treat the lumber cause standard iron fasteners to corrode and stain stuff faster.

In fact the code here in canada is all treated lumber must have some form of protected fastener used.

 

[bridgebuster]

Thanks SRE.

We call for fasteners to be HDG per ASTM A153. I have a feeling the PM will change everything to SS to avoid an argument with the architect. Of course, that leads to another potential problem: Stainless steel fasteners in galvanized steel connection angles.

 

[SlideRuleEra]

bridgebuster - Stainless steel fasteners bearing on hot-dipped steel members is ok. The other way around (i.e. galvanized fasteners on stainless steel members) can be a problem.

See this link:

http://www.galvanizeit.org/images/u...ss_Steel_in_Contact_with_Galvanized_Steel.pdf

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[msquared48]

Just swpec gold fasteners. Then the Architect will be satisfied with SS.

Mike McCann, PE, SE (WA)

 

[bridgebuster]

Guys, thanks for the responses. I looked at my e-mail a little while ago, the PM's going with SS fasteners and painted steel.


Mike - here's the problem with spec'ing gold fasteners: It'll take the architect a year and a day to decide if they should be white gold, yellow gold, or tri-colored gold.