To any of the structural gurus out there.... I'm designing a ranch home with a basement - concrete walls for both the basement and above grade walls - and I can't see any realistic way that the IRC allows for a construction joint at the main floor. I'm looking at strip form walls for basement (save cost) and ICF on above grade. I will pour extra thick walls for the basement and then block out 4" x 15" at the inside top of the basement walls to create a ledge for my flooring system. Now my construction joint will be right above my flooring system, but it seems that the IRC only wants the construction joint right at a "point of lateral support" or at the mid third of a reinforced wall between "points of lateral support" (i.e. between floors?). Am I interpreting this correctly? What is the purpose of this part of the code? If so, I'm not sure how anyone could realistically pour a construction joint right at the flooring system location of the wall? You wouldn't have anywhere to put the anchor bolts for the ledger boards (in the case that basement and above grade walls were ICF). In my case, then there is no way to find a good way to break between the ICF and basement walls. Any help greatly appreciated! Thanks.

Actually - now I think I may have figured it out....I think the code is trying to make sure that there is adequate support for "out-of-plane" forces through the use of steel reinforcing that overlaps the "points of lateral support". I think the assumption in the code (although not explicitly stated) is that the construction joint will occur above the floor (R611.6.3, exception #2).

I think this is pretty important to understand though when figuring out your construction joint no matter how you are doing this unless you are pouring basement and 1st story floors all together (which would have to be a huge pain?!). Still curious if there are any other folks who put a lot of thought into this issue?

I do strip forms for a living and do a considerable amount of commercial work, so I am very familiar with the typical standards.  You would not want a construction joint any where below you first floor because the main forces on foundation wall are from the soils on the outside pressing against it.  Any where above shouldn't be a problem, minimal lateral forces above.   Will your first floor be out of wood or concrete? 

I do agree with you that it doesn't make sense to have it below the first floor, but it just wasn't explicitly stated in the code. I was just looking for more the reasoning behind the code and how to interpret exactly what the IRC is asking for when they dictate having a construction joint at the location of lateral support. I will have a normal wood joist and OSB/plywood floor for my main level.

After much though, I think there are two things to consider at the construction joint.....tension forces and shear forces. I am thinking that the rebar for reinforcing the wall (i.e. for tension) must be continuous between points of lateral support, and so it isn't as important about EXACTLY where the construction joint is at the point of lateral support, but how the rebar extends across the joint and provides continuity for tension forces between the first floor and rafters. As long as I make sure the rebar is in tension between the first floor and rafters, then I should be good?

The extras (in addition to reinforcing) rebar that is required at the construction joint then (must have at least 1 #4 dowel every 24" on the joint) must be for shear forces - and this all must extend/be continuous across the point of lateral support. However, this is an educated guess and I'm trying to figure out if I'm "reading into" the code correctly so that I apply it appropriately.

Thanks.

Adding some #4s every 2 feet is more than adequate. 90% off the house foundations that I do have no rebar between the footing and the wall. Lot more forces at this point than ever will be experienced up above

Usually floors in icf construction (am aware basemennt is conventional) are hung from the inside
which will give you the most efficient assembly.
That being said why not put 1 row of icf on top the basement pour?
This will allow you to continu with ease with the rest of the build and construction joint will be above
the floor where you want it. This is the best way to do so regarding strenght, speed and code compliance.
Cheers!

thagreen - I thought about that, but I haven't really asked the strip form guys about it yet. Not sure how well that would work with their forms and experience....My ideal situation was to has a ledge though to provide extra support -- I'm an idealist :-)

Randy - I don't think the code calls for rebar to tie into the walls in the basement, but if not them i'm not sure exactly how much vertical rebar will even do?! You need to tie that rebar (lap splice) it in with the footings because that is your point of horizontal support that will allow the vertical rebar to flex between the basement floor and first floor. It is how they all do it in the commercial/industrial world at least...
BTW - do you usually key the footings?

jpj-
You've got a pretty good handle on it. The location of the joint isn't usually very critical, but I usually try to put it above the floor. The best thing, as I always say, is to have an engineer who knows what he's doing get it right for you. Then you won't have to worry so much about it.

Posted By jpj on 28 Nov 2011 12:44 PM
thagreen - I thought about that, but I haven't really asked the strip form guys about it yet. Not sure how well that would work with their forms and experience....My ideal situation was to has a ledge though to provide extra support -- I'm an idealist :-)

Randy - I don't think the code calls for rebar to tie into the walls in the basement, but if not them i'm not sure exactly how much vertical rebar will even do?! You need to tie that rebar (lap splice) it in with the footings because that is your point of horizontal support that will allow the vertical rebar to flex between the basement floor and first floor. It is how they all do it in the commercial/industrial world at least...
BTW - do you usually key the footings?

  You probably don't even need rebar. When I started, which wasn't too long ago about 15 years, the majority of the houses did not use any rebar.  The more corners the wall has the stronger it is to any outside lateral forces.  If a wall was 40' or longer and straight we would usually just switch to 10" thick.  I prefer rebar dowels over a keyway. I never had any issues with a key way, but rebar seems to me a better choice for holding the wall to the footing.  I have heard keyways were used to help hold water out of the basement, not sure how true that is though.  I wouldn't worry too much about vertical rebar, maybe add a couple dowels every 4' or for piece of mind at construction joints.  If we add rebar in houses it is always horizontals that we add first.  If you have any straight walls longer than 30', on commercial jobs we typical add a piece of chamfer to act as a control joint for cracking, you could add a little bar here if desired. Typical slices are 36 bar diameters, that is figured out like this say you need to figure out the splice for #4 bar this how the math would look 36 x 1/2 = 18" for #4. 36 x 5/8 = 22.5 for #5. This is minimum splice lengths.  Remember you always want to keep rebar at least 2" from form faces also

    I personally wouldn't consider pouring a floor without it being on a shelf.  I have never seen it designed this way, just being held in place with rebar.  If I were to build this, I would pour the floor over the entire top of the wall.  I would leave some #4 bar out the top of the wall with a bend on them.  I would then bend the rebar into you floor and pour it.  You now would have a level surface to setup your ICF's on. 
   Let me know if you have any more questions

Vertical steel is based on the height of wall and the height of backfill as well as the moisture and expansion of that backfill. The wall is restricted at the top by the floor and at the bottom by the slab so the verts are at least as important as the laterals, probably a lot more. Having said that, the last statement of Jerry's is still the way to go!!