galvanized bolts for pressure treated wood?

17513 Views 11 Replies 9 Participants Last post by Jeremy Hillary Boob, PhD, Jul 10, 2009

Jeremy Hillary Boob PhD

Discussion Starter · Jul 9, 2009

I'm building a shed which sits on pressure-treated wood. I've got "Simpson Strong Tie CB44 4x4 Post Column Base" (at least I think that's the model number) in concrete, much like you'd do for a deck. It's all connected together with 5/8" bolts. I'd read that non-galvanized bolts are OK as long as the diameter is 1/2" or greater, so I used regular steel bolts.

I started on this project last year, and the foundation and pressure-treated base was exposed to the elements over the winter---it is rainy and foggy all winter here. Just for fun, I removed one of the bolts, and it had some rust---a lot more than I would have expected in less than a year. Is this a problem? Do people actually use those outrageously expensive galvanized bolts for things like this or not?

Btw, I don't think I'll make any changes at this point, since I assume the "post column supports" will decay before the bolts (although, strangely, they still look pristine). So, this is more just out of curiosity and/or for future reference. Thanks.

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Mike Swearingen

· #2 · Jul 9, 2009

Most properly pressure-treated wood has a 50-year limited warranty. I've been using pt wood for decks, piers, docks, boathouses and bulkheading for more than 33 years here, and I have never used anything but galvanized bolts, nails and screws with it and never seen anyone else use non-galvanized with it.
The non-galvanized will rust out far, far sooner than the galvanized, and are a false economy. If you're going for any longevity at all, use galvanized, not to mention the unsightly rust running down the sides of your shed.
IMHO. Good luck!
Mike

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Maintenance 6

· #3 · Jul 9, 2009

So after one year, you've seen more rust than you expected. The question is how much will you see in two, three or more years and how long do you want this to last. Hot dipped galvanized or stainless steel are the only materials that have a chance against the latest generation of treated lumber. Do people really use these outrageously priced fasteners? Only the ones who want their projects to hold up. :yes:

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Jeremy Hillary Boob PhD

Discussion Starter · #4 · Jul 9, 2009

Mike Swearingen said:
Most properly pressure-treated wood has a 50-year limited warranty. I've been using pt wood for decks, piers, docks, boathouses and bulkheading for more than 33 years here, and I have never used anything but galvanized bolts, nails and screws with it and never seen anyone else use non-galvanized with it.
The non-galvanized will rust out far, far sooner than the galvanized, and are a false economy. If you're going for any longevity at all, use galvanized, not to mention the unsightly rust running down the sides of your shed.
IMHO. Good luck!
Mike

OK, you convinced me. It'll be easy (but not cheap...) to replace all of the bolts now, whereas once the shed is built it would be a real pain.

Can anyone recommend a good source for galvanized bolts? It seems the online sources are pretty reasonable compared to The Home Despot and places like that.

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Wildie

· #5 · Jul 10, 2009

In my area standard bolts are not allowed to be used with PT lumber.
The treatment chemicals cause iron bolts to corrode rapidly!

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Yoyizit

· #6 · Jul 10, 2009

Rusting slows once the surface layer excludes oxygen, but with these chemicals in wood I don't know what will happen.

"Due to the high risk of galvanic reaction between the copper-impregnated wood and any dissimilar metals, fasteners and flashings should be stainless steel and copper whenever possible. At the very least, you need to use better grades of galvanized fasteners."

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PaliBob

· #7 · Jul 10, 2009 (Edited)

Galvanized fasteners YES, But stay away from SS because the CB44 Galvanizing (zinc) and stainless steel are considered to be dissimilar metals which can cause the zinc to corrode when placed in contact with the stainless steel. This would result in the galvanized fasteners losing their protective coating faster than expected..
.

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hayewe farm

· #8 · Jul 10, 2009

AS I understand it the new PT treatment requires SS not galvanized fasteners.

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PaliBob

· #9 · Jul 10, 2009

The general rule is that if the fasteners (bolts) are SS then the connectors (post bases) must be SS and the same for galvanized fasteners > galvanized connectors.

hayewe farm said:
AS I understand it the new PT treatment requires SS not galvanized fasteners.

Yes and No, depending on where the ACQ is used..The latest requirements that I know of only Require SS for Permanent Wood Foundations and recommend SS for other severe applications.
Source:http://www.ufpi.com/literature/acqfastener-216.pdf

The OP may have ACQ because his installation is less than a year old and yards have been phasing in ACQ since 2004.

Now that I think about it the OP's quote:

I'm building a shed which sits on pressure-treated wood

would mean that that he has a permanent Wood Foundation so if he has ACQ he should be on Stainless Post Bases and SS Bolts

Any thoughts on this? Should he be using Stainless Steel?
.

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Termite

· #10 · Jul 10, 2009

Outrageously priced galvanized bolts? Ever price stainless?

1/2" or larger don't have to be galvanized (per code) although it is a good idea, especially when using treated material. PaliBob's right about dissimilar metals reacting with each other as well.

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Scuba_Dave

· #11 · Jul 10, 2009

I've always used galvanized on decks/outside, never considered anything else
I did use normal lags (I think) on a ledger board for ceiling joists in my sunroom
It's inside, no outside exposure

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Jeremy Hillary Boob PhD

Discussion Starter · #12 · Jul 10, 2009

thekctermite said:
Outrageously priced galvanized bolts? Ever price stainless?

1/2" or larger don't have to be galvanized (per code) although it is a good idea, especially when using treated material. PaliBob's right about dissimilar metals reacting with each other as well.

Yes, I'd seen the code requirement somewhere and thought that was that. I've ordered the galvanized bolts and it wasn't as expensive as I thought. I'm sure I'll eventually find a use for the other bolts, so no loss, except for my time.

Btw, my local Home Depot doesn't carry galvanized bolts larger than 1/2", so I bet most people are using non-galvanized bolts with PT wood.

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galvanized bolts for pressure treated wood?

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