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spencerin
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# Posted: 6 Apr 2020 08:41pm
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IRC appears to permit the use of zinc-plated (non-galvanized) bolts in pt wood if the bolt's diameter is 1/2"+. Can anyone explain why? I've seen UC4A pt wood eat zinc-plated washers for lunch after only a year, so I can only imagine what's happening to the bolt inside the wood. If it's a thickness/mass thing, wouldn't the wood continue to corrode the bolt until the point of failure? It doesn't make sense to me that code would allow it, unless I'm misreading what the exception is.
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curious
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# Posted: 7 Apr 2020 10:45am - Edited by: curious
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Can you point to where that is in the IRC? Seems odd?
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spencerin
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# Posted: 7 Apr 2020 07:22pm
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Here's what I often see cited out of 2009 IRC -
"Fasteners for pressure-preservative and fire retardant-treated wood shall be of hot-dipped galvanized steel, stainless steel, silicon bronze, or copper. Exception - one-half inch diameter or greater steel bolts....."
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Brettny
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# Posted: 8 Apr 2020 09:49am
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Hot dipped galv is not zink coated. But it does appear that they allow anything over 1/2in size. You might ask your building inspector about this first.
But if they do any decent hardware store should have 5/8 threaded rod.
How much of your foundation is PT? In our 20x32 with post on sono tube foundation il only need 36 hot dipped galvanized bolts. I may even use 5/8 galv due to the strength and longevity of them.
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ICC
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# Posted: 8 Apr 2020 10:35am - Edited by: ICC
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I have wondered about the exception reasoning. I have never found an explanation of the technical reasoning behind it. It does seem the reasoning is because of mass. I dunno for sure.
What I do know though is that for corrosion to take place you need moisture. IF for example, the fastener is to secure a PT mudsill and the structure is well built that sill will never be wet, so corrosion will not be a factor.
We always used 5/8 j-bolts for that application. I have had jobs where we ripped apart 40 to 50 year old walls like that and have found no unusual corrosion. Dry.
However, the hardware manufacturer may place limits on locations that are not dry and may specify certain types of connectors and fasteners when wet, exposed, salt air, etc.
Quoting: Brettny Hot dipped galv is not zink coated
I'm not sure what you mean by that comment. Galvanizing uses zinc. It is either hot dipped or electroplated. Bright and shiny or rough and dull, but zinc all the same.
There are specs as to how much zinc must be used (ounces per square foot) to meet the various uses. Electroplating does not deposit enough zinc to meet most PT uses.
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spencerin
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# Posted: 8 Apr 2020 08:12pm
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I guess I'm just curious if they would last a long time (50+ years) in a UC4A pt wood foundation in a low-to-no-load capacity exposed to typical IN weather conditions.
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spencerin
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# Posted: 8 Apr 2020 08:14pm
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By "they" I mean 1/2" zinc-coated bolts.
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ICC
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# Posted: 8 Apr 2020 09:15pm - Edited by: ICC
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Quoting: spencerin By "they" I mean 1/2" zinc-coated bolts.
Hot-dipped or electroplated??? Not sure I understand which ones you are wondering about when you say zinc-coated---
Where I buy most of my fasteners the plated zinc bolts are slightly more expensive than the hot-dipped. Hot-dipped are my choice for things where I don't mind the rougher appearance and want the greater corrosion resistance, but don't want to spend the extra for stainless steel. Get the special hot-dipped nuts too as they do not interchange. The nuts are a little more costly in hot-dipped for some reason IIRC.
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spencerin
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# Posted: 8 Apr 2020 10:01pm
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Electroplated, or the "shiny" kind in common parlance. HDG would last, but the electroplated being considered is also 1/2", which I'm wondering IRC implies would still be fine in the long-run.
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