Double Bottom Plates??

xavieralumniJanuary 29, 2008

My home is currently in the framing stage. One peculiar thing I've noticed is that my framers have put double bottom plates on the exterior walls. Of course the one closest to the concrete is treated, but the one that sits on top of that one is untreated. Has anybody heard of using two bottom plates before? I'm just curious.

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It depends on the framing method and the foundation type. There is not just one way to build a house.

    Bookmark   January 29, 2008 at 11:13AM
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Pretty standard around here in TX.

    Bookmark   January 29, 2008 at 11:34AM
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Houses in TX are usually built on slab foundations so they have double sole plates. In New England they are built on basement walls so they have a pressure treated sill, then a band joist, then a sole plate under the wall studs. We don't know what or where you are building.

    Bookmark   January 29, 2008 at 11:48AM
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Provides extra fastening for exterior wall sheathing, sidings, flashings/weep screeds for stucco, etc.

Provides extra fastening for interior wall board, wider base boards, toe kick installs,etc.

Considered structural especially in seismic areas where in strategic areas, foundation bolts are required to be 8"o.c. depleting the bottom sill plate of integrity because of the many bolt holes. The upper bottom plate provides that along w/ the extra fastening advantage.

    Bookmark   January 29, 2008 at 11:55AM
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Generally only used on slab foundations as m.a. stated.

    Bookmark   January 29, 2008 at 11:57AM
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It is not necessary to space anchor bolts 8" apart in any jurisdiction that I am aware of unless required by an engineer for a special condition. In any event it is still necessary to pick a framing method before making generalizations about plates.

    Bookmark   January 29, 2008 at 12:15PM
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Hi Mighty, 8"o.c 5/8" foundation bolts were/are required in some areas of southern ca. along w/ simpson foundation ties that are an integral part of the footing. Mostly seen in commercial applications, it has been required on residential builds in some areas and imo, does more harm than good because it completely renders the bottom sill plate useless w/ so many bolt holes as well as if the double bottom plate system is used, very dependent on the concrete crew ahead of you for proper height placement of the bolts. You still have to bore out the upper bottom, but if done right by the creters, not all the way through, so in that case, it helps, but still dpeletes the load and nailing value of the plate(s), again only in my opinion as im not an engineer but have seen many improper place foundation bolts in the framing days w/o consideration for stud layout and openings. I think things are better theses days.

Doubled bottoms are also common on garage stem walls as well.

    Bookmark   January 29, 2008 at 12:42PM
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Ca. is changing over to the i.b.c. effective by '09. The 8" o.c placement could very well be an engineered requirenment but still coinciding w/ codes. It's nice to see that ca. is finally getting on the same page w/ the rest or most of the country. They are coming up w/ more stringent energy codes under article 24.

    Bookmark   January 29, 2008 at 12:46PM
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When the IRC requires 8" o.c. bolts you can opt for using ACI 332 which is far more reasonable.

If I were in earthquake territory I would be asking an engineer to design the foundation.

    Bookmark   January 29, 2008 at 1:06PM
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Out here they are as well as the structural elements including shear, ties, strapping, hold downs,etc from foundation to the roof framing. All by a licensed engineered coinciding w/ current codes and im sure that will be the continued m.o even w/ the change of '09

    Bookmark   January 29, 2008 at 1:25PM
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The Ontario Building Code [at (2)] requires anchor bolts at a maximum spacing of 2400 mm o.c., (a little less than 15 ins.).

    Bookmark   January 29, 2008 at 2:10PM
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Correction: a little less than 15 ins. 94.488 in.

    Bookmark   January 29, 2008 at 2:15PM
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We are in Maine and we have a triple sill plate, bolted down. Double seems to be the standard that DH always does when he frames, and they did the additional one for some reason I can't remember.

    Bookmark   January 29, 2008 at 3:02PM
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OP is in Lousiana if I remember correctly. Most likely slab foundation.

    Bookmark   January 29, 2008 at 3:49PM
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