does the irc require pressure treated bottom plates on a slab on grade house?

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does anyone know if the irc requires treated bottom plates on partition walls on a slab on grade house? is it acceptable to use white wood with a capillary break such as tarpaper on the bottom?
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I just completed an addition to my wife's commercial daycare and was required to use treated wood for a bottom plate on a concrete slab. I did this in Auburn,WA which is in King Co. but I would check with you're local authority where you get your building permits. marson wrote:

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In a previous post marson wrote...

The relevant section is IRC2003 R319.1. This section allows the use of untreated sill plates and sleepers if the wood is separated from the concrete by an impervious moisture barrier.
However, it seems to me that the cost of using treated plates in this instance is pretty nominal so why not go ahead and use them? I would think you would spend more horsing around with the "tar paper" than it's worth.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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thanks once again Bob. I definitely agree that you should use treated bottom plates. In this case, someone in our company framed partitions without and I'm just wondering if I have to them go back and change them. The building inspector didn't even know if it was in the code or not!
Bob Morrison wrote:

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Use actual stainless steel 1/2" all-thread in the slab, and stainless bolts and washers to hold the plate to the slab. Use ceramic screws if already poured slab. Both are used to holdup against chemicals used in current treated lumber. You will need galvanized nails, or non-ferrous or treated screws to hold the treated lumber to the studs. Same reason. There are galvanized nails out there that don't have much zinc, be careful.
Maybe you should invest in your own hired home inspector. The municipal code inspector is not there to protect you by any means.
15# felt is standard under the bottom plate. Don't matter if its standard lumber or treated lumber. It should be 4" wide if the bottom plate is 2X4. The inside should be flush with the inside of the bottom plate. This gives 1/2" overlap downwards outside with the felt paper. This causes any water intrusion to fall below the bottom the plate. Wider bottom plate requires same 1/2" protrusion to the outside and folded downwards. Any sissy framing carpenter's helper can cut #15 felt to the proper width on the roll. And follow the chalk line on the layout on the slab. Its not big deal. I'd go with the treated lumber for the long term. Not because of anything else.
--
Jonny
"marson" < snipped-for-privacy@gmail.com> wrote in message
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Bob Morrison wrote:

Do you specify fasteners that won't corrode at an accelerated rate in the ACQ? The metal connector tie downs and the hanger nails are corrosion resistant with ACQ already, but the sheathing and stud/plate fasteners should also be specified resistant. The shear walls are of particular concern.
R
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If hot dipped galvanized fasteners are needed in nailing into the bottom plate if it's ACQ treated lumber, then there are a lot of builders out there in trouble. I don't know of anyone who is doing that, and i've never seen that spec on a plan. You just try to get a framer to dig out his galvy hand bangers to nail off the bottom plate. It just isn't happening.
I use treated bottom plates as I said before, but I do think it's overkill. if you have enough moisture in your slab to rot your bottom plate on an interior partition, then what about your drywall, not to mention your finish floor coverings? Plus, I have taken apart numerous buildings that had good old white wood against concrete that were fine--including my own seventy year old house which not only has untreated mud sills but has concrete poured between the joists.
RicodJour wrote:

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In a previous post marson wrote...

Unfortunately, that is all too true. However, the bottom edge nails will corrode after a fairly short period of time and that nice shear wall will no longer be of any value. IRC and IBC require stainless steel or hot- dipped fasteners when connecting PT lumber. The framers need to be made aware that if they are not doing this, then they are not following the code. And, building inspectors need to enforce this provision.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Bob Morrison wrote:

Yep, this is a perfect example of the "law of unforeseen/unintended consequences" and a case where the cure is likely to be far worse than the disease ever was or would have ever been... :(
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What if they're using "cement coated" nails ? Will that protect the metal from the ACQ ?

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Rudy wrote:

The cement coating is an adhesive and not designed as a protective coating. Will it help extend the life of the nails? Possibly - but possibly is not a desirable result in structural engineering circles.
R
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Is this corrosion a problem only while the PT lumber is still wet from the PT process, or does it continue to occur after the PT lumber has dried?
I'm retrofitting shear walls on a foundation installed 2.75 years ago with ACQ sill plates. Untreated nails that had been installed in the sill plate over 1 year ago and recently removed show no signs of corrosion. My work so far has been with standard nails; wondering if I need to install SS nails between the standard nails on the sill plate.
Cheers, Wayne
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Wayne Whitney wrote:

ACQ is relatively new territory. Wet PT lumber is far more of a problem, but it is unclear at what rate the corrosion will proceed as the wood dries out. Guesses don't work in structural engineering. The few extra bucks for corrosion resistant fasteners is money well spent.
R
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After making this statement, I realized that I hadn't really been paying attention to the nails I had been removing. So I pulled some nails I had installed 2 years ago, 4 nails from one piece of the sill plate and 4 nails from a cripple stud, and I took a closer look.
The nails from the cripple stud basically looked the same as unused nails, finish wise. The nails from the sill plate did show some signs of corrosion: the yellow/silver zinc dichromate finish was missing in spots, anywhere from 10%-40% of the surface area of the nail, and they all showed a few spots of brown rust at the point.
Based on this level of corrosion, if I want the nails to be structurally sound in 50 or 100 years, do I need to use corrosion resistant nails?
Thanks, Wayne
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In a previous post Wayne Whitney wrote...

Wayne:
AS I said in an earlier post: my specifications require the use of corrosion resistant fasteners when connecting to PT lumber. So, I recommend that you use HD galvanized nails when putting together any pieces attached to PT lumber.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Bob Morrison wrote:

Bob,
Just a side note. I no longer use the term "HD" galvanized nails. I had a client that asked my advice about building a deck and I told him to use HD galvanized nails. The next time I saw him, he was using zinc coated nails on his deck. When I pointed out to him that these were not the ones I specified, his reply was: "Yes they are,... they are from Home Depot!" (HD)
As my father used to say: You can't make anything foolproof, 'cause fools are too ingenious.
--
Robert Allison
Rimshot, Inc.
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In a previous post Robert Allison wrote...

Robert:
Thanks for the chuckle! My structural notes do spell out hot-dipped galvanized.
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Bob Morrison, PE, SE
R L Morrison Engineering Co
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OK, good enough, if that's the standard, I guess I shouldn't mess around trying to figure out if it really is necessary in my case.
Now I need to redo some nailing I already did with standard 8d common nails 4" o.c., between the 1/2" struct one plywood and the PT 2x6 sill plate. Would it be a problem to interleave corrosion resistant 8d common nails, yielding a 2" o.c. straight nailing pattern?
Thanks, Wayne
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In a previous post Wayne Whitney wrote...

That's pretty close nail spacing. My inclination would be to recommend that you put one galvanized nail every other space, or that you put the galvanized nail right next to (1/2") the plain nail.
Another option is to add blocking between the studs on top of the existing sill. Fasten the blocking to the PT sill with galvanized nails, then put in a row of plain nails through the sheathing into the untreated blocks. Kinda of a pain in the backside, but it depends on how much work you want to do.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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OK, thanks, I think I'll do both of these, put two new nails in between two existing nails, at the ends of the space, and then skip a space. So the spacing will be {1/2", 3", 1/2", 4", repeat}.
Cheers, Wayne
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