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

Discussion in 'Building Construction' started by marson, Oct 23, 2006.

  1. marson

    marson Guest

    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?
    marson, Oct 23, 2006
    #1
  2. marson

    bodega Guest

    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:
    > 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?
    bodega, Oct 23, 2006
    #2
  3. marson

    Bob Morrison Guest

    In a previous post marson wrote...
    > 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?
    >


    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
    Structural & Civil Engineering
    Poulsbo WA
    bob at rlmorrisonengr dot com
    Bob Morrison, Oct 23, 2006
    #3
  4. marson

    marson Guest

    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:
    > In a previous post marson wrote...
    > > 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?
    > >

    >
    > 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
    > Structural & Civil Engineering
    > Poulsbo WA
    > bob at rlmorrisonengr dot com
    marson, Oct 24, 2006
    #4
  5. marson

    RicodJour Guest

    Bob Morrison wrote:
    > In a previous post marson wrote...
    > > 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?
    > >

    >
    > 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.


    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
    RicodJour, Oct 24, 2006
    #5
  6. marson

    marson Guest

    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:
    > Bob Morrison wrote:
    > > In a previous post marson wrote...
    > > > 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?
    > > >

    > >
    > > 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.

    >
    > 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
    marson, Oct 24, 2006
    #6
  7. marson

    Rudy Guest


    >>is it acceptable to use white wood with a capillary break such as tarpaper
    >>on the bottom?


    Sure, use white plastic mudsill gasket material..the polyfoam stuff thats
    about 1/4" thick X 4" or 6" and comes in rolls
    Rudy, Oct 24, 2006
    #7
  8. marson

    Bob Morrison Guest

    In a previous post RicodJour 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.
    >


    Yes. Here are a few selected lines from my "Structural Notes":

    Sill anchor bolts shall be hot dipped galvanized or stainless steel, 1/2"
    minimum diameter, with a minimum embedment of 7 inches, unless noted
    otherwise on Shear Wall Schedule or Foundation Details. Bolts shall be
    tied in place prior to pouring concrete and shall not be "wet-set" or
    "stabbed" into wet concrete.

    Connectors and fasteners for pressure treated wood shall be hot-dipped
    galvanized or stainless steel in accordance with IBC Section 2304.9.5.

    Hardware for pressure treated wood shall be hot-dipped galvanized or
    stainless steel in accordance with IBC Section 2304.9.5.

    --
    Bob Morrison, PE, SE
    R L Morrison Engineering Co
    Structural & Civil Engineering
    Poulsbo WA
    bob at rlmorrisonengr dot com
    Bob Morrison, Oct 24, 2006
    #8
  9. marson

    Bob Morrison Guest

    In a previous post marson wrote...
    > 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.
    >


    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
    Structural & Civil Engineering
    Poulsbo WA
    bob at rlmorrisonengr dot com
    Bob Morrison, Oct 24, 2006
    #9
  10. marson

    dpb Guest

    Bob Morrison wrote:
    > In a previous post marson wrote...
    > > 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...

    ....
    > 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. ...


    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... :(
    dpb, Oct 24, 2006
    #10
  11. marson

    Goedjn Guest

    On Mon, 23 Oct 2006 22:22:32 GMT, Bob Morrison <>
    wrote:

    >In a previous post marson wrote...
    >> 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?
    >>

    >
    >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.



    Yes, but sheet-metal termite barriers serve both purposes.
    Goedjn, Oct 24, 2006
    #11
  12. marson

    Rudy Guest

    What if they're using "cement coated" nails ? Will that protect the metal
    from the ACQ ?
    >
    > 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
    > Structural & Civil Engineering
    > Poulsbo WA
    > bob at rlmorrisonengr dot com
    Rudy, Oct 26, 2006
    #12
  13. marson

    RicodJour Guest

    Rudy wrote:
    > What if they're using "cement coated" nails ? Will that protect the metal
    > from the ACQ ?


    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
    RicodJour, Oct 26, 2006
    #13
  14. On 2006-10-24, Bob Morrison <> wrote:

    > In a previous post marson wrote...
    >
    > > 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.

    >
    > 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.


    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
    Wayne Whitney, Oct 26, 2006
    #14
  15. marson

    RicodJour Guest

    Wayne Whitney wrote:
    >
    > 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.


    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
    RicodJour, Oct 26, 2006
    #15
  16. On 2006-10-26, Wayne Whitney <> wrote:

    > 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.


    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
    Wayne Whitney, Oct 26, 2006
    #16
  17. marson

    Bob Morrison Guest

    In a previous post Wayne Whitney wrote...
    > 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?
    >


    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
    Structural & Civil Engineering
    Poulsbo WA
    bob at rlmorrisonengr dot com
    Bob Morrison, Oct 26, 2006
    #17
  18. Re: does the irc require pressure treated bottom plates on a slabon grade house?

    Bob Morrison wrote:
    > In a previous post Wayne Whitney wrote...
    >
    >>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?
    >>

    >
    >
    > 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,

    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.
    Georgetown, TX
    Robert Allison, Oct 26, 2006
    #18
  19. On 2006-10-26, Bob Morrison <> wrote:

    > 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.


    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
    Wayne Whitney, Oct 26, 2006
    #19
  20. marson

    Bob Morrison Guest

    In a previous post Robert Allison wrote...
    > 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:

    Thanks for the chuckle! My structural notes do spell out hot-dipped
    galvanized.

    --
    Bob Morrison, PE, SE
    R L Morrison Engineering Co
    Structural & Civil Engineering
    Poulsbo WA
    bob at rlmorrisonengr dot com
    Bob Morrison, Oct 26, 2006
    #20

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