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In residential construction, placing anchor (j bolts) for the sill plate, I have always read that it's best to stay towards the outside edge of the foundation and face the J portion towards the interior of the home. For an 8" thick concrete wall, I have always used ~3" in from the edge. This allowed a 2x6 plate to have the anchor be about 1/4" off center of the board.

Wondering how you guys do it, and if there is a better way. I always try to get the concrete guys to provide 10" instead of 8" bolts, and they are typically 5/8" diameter.

Also - Do you actually preset the anchor bolts in blocks of wood or rebar cages, so that the hook part of the J slips under the top horizontal rebar?

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  • The short answer is that it doesn't much matter unless you're trying to meet particular requirements for high-stress situations, such as in earthquake zones. For most of the U.S., anyway, the soft parts of a house will tear away in a tornado before even a casually-placed anchor bolt will pull out. You might refine your post to ask something more specific or you'll mostly get a bunch of opinions.
    – isherwood
    Commented Aug 26, 2019 at 14:56
  • @isherwood Just trying to get some general input, not really specific for what load. It may sound stupid, but I do not believe our concrete boys in this area ever pay attention to hooking the J bolt into rebar. In addition, our inspector never really comes to check that because the J bolts are placed after floating the top of foundation, and inspector only shows up to check the rebar installs. I also think that the length of bolt would be crucial to hooking the top piece of rebar depending on how they tied it off.
    – CCCBuilder
    Commented Aug 27, 2019 at 14:31

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The Code requires an edge distance based on the size of the bolt:

1) 1/4” = 1 1/2”

2) 1/2” = 2 1/2”

3) 5/8” = 3”

This is based on standard grade concrete, (i.e.: 2500, 3000, etc.) If you use a “high-strength” concrete it can be reduced. (See ICC Chapter 19, Table 1908.2)

Generally, I see “J-bolts” installed after the foundation wall is poured. This is primarily because we want a smooth surface for the sole plate to rest on. The bolts can be wiggled into the concrete and twisted so it hooks under the top horizontal rebar, which should be approximately 3” clear down from the top of the wall.

Yes, 10” anchor bolts are now required with 3” square washers in any high-wind or seismic area.

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  • So the J or leg of the anchor has to face towards the interior of the structure especially if it's hooking the rebar. Assuming they install rebar properly and it's set in 3" from the edge, that would mean the J bolt is 2-1/2" from the edge of the rebar. However, I haven't met a contractor who keeps that tight of ship and places rebar exactly where it should, nor do they hold it when pumping in concrete. I'm trying to find the post or article I read discussing the orientation of the anchor J bolts, the depth, and the diameter. Do you know what code discusses hooking the J into rebar?
    – CCCBuilder
    Commented Aug 27, 2019 at 14:34
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    @Nic Perhaps just logic. Those clearances are for developing “full strength”. Seldom, if ever, are we looking for full strength. The Concrete Reinforcing Steel Institute (CRSI) requires 3/4” minimum for concrete with 3/4” aggregate and 1 1/2” for 1 1/2” aggregate. They also require 2” for “high corrosive atmospheres” on sides and 3” clear on bottom. Actually, to develop full strength you’d need to use an 8” stem wall for 5/8” anchor bolts...but often we use a 6” stem wall.
    – Lee Sam
    Commented Aug 27, 2019 at 16:25
  • @LeeSam Been looking for where 10” anchor bolts requirement came from. would you happen to recall? I didn't see it in the 2021 IBC or IRC
    – Joe B
    Commented Aug 20 at 22:43

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