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Question DetailsAsked on 8/21/2015

Replacing sections of termite damaged sill plate on concrete slab. Code asks for 7 inch anchor. Slab is 4 inches.

So if code is followed with the 7inch depth anchor that would mean that I would have to go through the slab and into the other sections of the foundation. How can this code be satisfied.

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2 Answers

Voted Best Answer

Not seeing your exact configuration might mean my answer is off a bit - if in doubt, contact your local building department code complaince office:

1) If a thickened edge slab (4" slab but maybe 8-10" thick around the edge (thickened downwards into the dirt) as a slab edge stiffner to carry the wall loads) then you would probably have enough for the 7" embedment - using anchor grout and all-thread bolt material, or overdrilling the hole size enough to get a headed bolt down in the hole

2) if a slab on strip footer or concrete block wall - then you have foundation wall below that point. If strip concrete footer same situation as above - drill in the 7" with carbide bit (probably hammer-drill for the diameter hole you need) and put in grout, then shove bolt in full depth. If a block wall, the cells with the bolts have to be fully concreted/sanded grout filled to hold the bolt, so if going in new cells you might have to drill a larger hole to pour or pump properly mixed grout in, then install the bolt.

3) if truly a 4 " slab, check with buyilding department - probably will require a larger diameter hole and bolt and an expansion type anchor instead, grouted in after installing and tighening the anchor / bolt.

Now enough of the hard version - since this is an existing wall if the bolts are already there and not badly corroded, if you are replacing damaged studs also just reuse the old bolts - predrill the new treated sill plate for the bolts, slip down over the bolts, then install the studs and toenail or Simpson bracket them to the sill plate. If only replacing the sill plate and slipping it in under the studs, I would drill for the bolts as if slipping down over, then cut a slot through to the inside face of the plate (so as not to provide an insect path) so the plate can be slipped horizontally onto the foundation and bolts, fill the cut out slot with a tightly fitting piece of wood with construction adhesive, then nail in a Simpson metal tie plate rated for joining 2x4 on each side of the cutout - like a Simpson HRS8 would probably be appropriate, though there are longer MSTAM and HRS plates that will also fit the side of the plate. NOTE - if a finish wall area (as opposed to unfinished basement or garage or such) you might want to chisel or saw back the plate by the thickness of the plate and fastener heads so the drywall does not toe out at the bottom - guess that ewould be called a full-thickness rabbet ? Or maybe just a recessed cut.

Answered 4 years ago by LCD


It's a wall, no basement. The section is about 4 feet on a 12ft wall that borders the house, an "outside wall" I noticed that I didn't have any anchors per say. It did have concrete nails that seemed to have rusted away. Inner walls on same room did have anchors, the older ones with square lugs and round washer. I have to point out that this is a 1950s home that has 12inch walls made out of brick/some type of dirt. On the inside of that are the wood frames.

Answered 4 years ago by plebe3


Since the anchor would be in brick (useless unless bracketed in, which requires significant brick work) or dirt infill (useless anyway - BTW, this is quite likely coal power palnt flyash insulation, or perhaps a dry clay).

Two things I see:

1) talk to building official (especially if this is being inspected) about using a 4 inch long grouted in or expansion anchor instead, or maybe a 3/4 rather than 1/2" anchor. Or they might say just put in twice as many - halve the interval. This makes the most sense - you are only talking a short length of plate. Code generally requires at least two bolts per section of plate, and two of them have to be not more than 1 foot from each end. Spacing can also not be morer than 6 feet - so plate lengths up to 8 feet require only 2 bolts, 1 a foot in from each end. In your case, I would just put in 3 or 4 bolts 4 inches long instead of the minimum 2.

2) drill oversize for grouting (say 1 inch) and put in a 7 inch embedment length 1/2" grouted in anchor - no one will know the bottom 3 inches is doing nothing because it is dirt rather than concrete fill as it should be in the brick wall - and of course double up the number of bolts so they actually hold. Of course, if you have the top of the brick wall open after removing the rotted plate, then you can dig/wash out the infill under the bolt locations and put in concrete/grout to the specified depth and all is good.

BTW - the code actually says 7" embedment length in poured concrete - it is 15" embedment length in masonry or concrete block walls, embedded in the concrete/grout filled core it penetrates.

Answered 4 years ago by LCD

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