I have a flooring question.  On a traditional basement pour, the walls are laterally supported by the floor system.  The sole-plate is anchored to the top of the concrete walls, the joists are nailed to it, and the decking is nailed to the joists . . .  If the backfill portion is running parallel to the joists, there is suppose to be blocking between the sole-plate and the bottom of the joists to provide adequate lateral support.

Now my question:  How is the lateral support achieved with ICF two-story houses?  Lets make my house a simple rectangle with the north and west sides open as a walk-out, and the east and south sides receiving backfill.  The open-web floor trusses are running north/south.  So I have a top-bearing floor truss sitting on a ledger board on the south wall, and the other end of the truss is bottom bearing on a load bearing wall.  With the ledger board and the floor system, the south side wall should be supported well.  But, the east side wall has no ledger board and there will be some simple nailers screwed to the webs to support flooring/drywall ceiling against the wall.  Any lateral support that exists will be through the foam.  Is this sufficient? 

An option would be to cut some foam out from behind the nailers and place wood blocks to transfer load from my nailers to the concrete, and then block between a few floor trusses (or put them in-line with the strong-backs).

What do you guys typically do?

Sean

Doesn't your local code specify bridging or blocking panels for lateral joist support in any case? I haven't seen many ICF builds, but, so far, they have all had a ledger board ( w/anchor bolts ) on the parallel walls as well.

Unless you don't care about overbuilding the ICF wall, the height and thickness should be part of an engineered solution, and your first floor supports whether it is lumber, trusses or some floor system will affect it.

I don't have this problem since I mono pour my footing and walls together. If I didn't , then you could leave your bracing on when you back fill then pour your floor. The other option is to install your floor system. The deck will brace the walls, even the walls perpendicular to the trusses

I don't have this problem since I mono pour my footing and walls together.

Isn't the issue of backfilling with or without bracing (be it the flooring support or removeable form support) separate from the overall issues of structural engineering?

So let me get this straight...you have 4 walls, two are backfilled (front and side) and two are walkout (back and other side).

The joists run front to back, the front is top chord fastened, the back is bottom chord fastened and both sides are a couple of 2x screwed to the webs merely to support the subfloor above and drywall below.

Well, first off, the front and side wall that get backfilled, what is the footing size? what is the backfill height? what is the backfill material? Who designed the floor system? Were they aware this is an ICF house? Have they dealt with ICF designs before?

Did you use an engineer to design this? or did you just pull everything out of the IRC?

Sorry but your question was a little confusing and the answer you need requires a lot more questions answered...and I may be missing a few questions still

Posted By Chris Johnson on 24 Jun 2011 06:02 PM
So let me get this straight...you have 4 walls, two are backfilled (front and side) and two are walkout (back and other side).

The joists run front to back, the front is top chord fastened, the back is bottom chord fastened and both sides are a couple of 2x screwed to the webs merely to support the subfloor above and drywall below.

Well, first off, the front and side wall that get backfilled, what is the footing size? what is the backfill height? what is the backfill material? Who designed the floor system? Were they aware this is an ICF house? Have they dealt with ICF designs before?

Did you use an engineer to design this? or did you just pull everything out of the IRC?

Sorry but your question was a little confusing and the answer you need requires a lot more questions answered...and I may be missing a few questions still

Thanks for the response from all of you. 

Chris, let's use your example, since this is a fictitious build, for all practical purposes.  I have a basement that I have to laterally support, but this simple rectangle should give me what I need to know to deal with this ICF  build. 

I would have to believe that simple nailers to the web wouldn't be enough to prevent lateral movement, although I've been told that this is what most builders do.  The footing is 24" wide by 12" deep in the backfill sections.  Wall height from the top of the footing to the bottom of the floor trusses is 8'8".  The slab is 4" thick.  The unbalanced height is about 7'.  The backfill material will be crushed stone tapering from the footing to 8' above the footing.  Fabric will separate the stone from the soil, which is mainly clay. 

The floor system was designed by the truss company and they were aware that it is an ICF house.  I don't think they deal with ICF too much around here.

No engineer.  Just me and the IRC.

The longest wall that has backfill where the floor trusses run parallel to the wall is about 26'.  The sub-floor is flush with the top of the basement forms.  I can wrap the ends of the sub-floor with felt and pour the first floor walls up to the edge of the sub-floor, but this would be above a cold-joint. 

I'm thinking of drilling some anchors before I put up some nailers to transfer loads from the concrete to the floor system.  What do you think?

If the rim board is not properly secured to the concrete than you have a big issue, attaching to the webs only is not strong enough to support the weight of the floor system.

That rim board needs to be secured to the concrete with one of many systems available to us, i.e. Simpson, ICF connect, Anchor Bolts, etc.

If it is connected properly on all four sides and the sub-floor is installed than you will have sufficient lateral support, based on the to 'locking' effect of the diaphragm from the joist/sub-floor combination and the correct positioning of the vertical rebar in the below grade walls.

What may be of concern to some is the walkout situation with backfill on two walls 7' higher than the opposing two walls, this may have required a larger footing since the backfill pressures are not equal on all four sides, essentially the two backfilled walls are now acting as a retaining wall which could have required opposite positioning of the vertical rebars.

The fact you are securing the bank with filter cloth and backfilling with clear gravel has alleviated a lot of pressure off the walls (As opposed to the original clay) is good and may calc out without issue of my concern.

Cold joints are frowned upon, but if you must have them (which we all do) they are best at the floor system where there is support (the diaphragm). Above or below this area can create a hinge point...in theory...

You shouldn't need to protect the edges of the sub-floor as it should not go past the face of the ICF. If you are think of running this into the face of the concrete, i.e. cutting the foam, then I suggest you hire a local engineer to review the mess you may have gotten yourself into. Simpson as an example does make many products for the retrofit market that may work in your situation if you have missed critical connection points.

I hope I don't overly offend too many people when I say this here....structural is not a hobby, a lot of what we do looks easy and goes together fairly easy, but experience is what puts all the pieces of the puzzle together and if you miss something important it can be either costly to fix or disastrous at some point. I have no issue with the DIY guy doing his own ICF, but if you have little to no experience and are trying to save money, hire an experienced helper or an engineer to review everything, before during and after the build.

Thank you Chris for you comments.  The ledger boards are mounted to the concrete through the simpson ICF-VL.  They carry the weight of the floor system.  The only place where there isn't anchor bolts/simpson brackets are the ICF walls that have joists running parallel to them.    The floor system isn't installed yet, so I can address the issue now.  I don't think it's that big of a mess.  If I have to drill, epoxy, and install anchor bolts, so be it.   There aren't many people in my area to consult with, that I know of.  The few that I have, have said what I stated in the original post "that most run a nailer to the webs."  I don't feel comfortable with that, so that's why I posted the question here.

Thanks again for your quick response.

Sean

Okay but you could still be dealing with a shear issue since that piece of ledger is going to have 2 5/8" unsupported between the back of the ledger and the face of the concrete...foam has no structural support.

Do you have 3x material available locally?

Remove the foam, 6x6 area should be fine, use that space to the concrete as the area to apply solid backing, namely the 3x material. You may need to use 2x and plywood to build up to the 2 5/8"

Drill and epoxy the threaded rod all the way thru, once torqued tight this will be solid and secure

Another way to address shear loads on those anchor bolts is to cut the foam out to 3" to 4" diameter around the bolts, then slip a piece of 3" or 4" steel pipe over anchor bolt - length of pipe cut to match the thickness of the foam. Another option is to use 4" schedule 40 PVC pipe instead of the steel pipe and fill the inside of the PVC pipe with non-shrink precision grout.

So the conclusion is rim boards tied to the concrete on all 4 walls and then blocking between the rim board and the first joist on the two walls parallel to the joists?

Arkie and Chris, that was what I was originally thinking, and I appreciate your responses. That was why I posted this in the first place. I didn't feel comfortable with foam between my parallel ledger and the wall. I have a home-made hole saw that uses my cordless drill and a piece of PVC that cuts through foam nicely. I was planning on screwing my ledger boards into the webs along a caulk line, drilling 5/8" holes through the board, foam and concrete, pulling the ledger off and core drilling my foam, epoxying the bolts, then grouting the foam holes. Arkie, is there a reason for the pvc? Wouldn't using the foam as a form for the grout work?

On a side note, many builders don't block on conventional non-icf basements, even though the 06' code states blocking for the full depth of two joist cavities, then a 2x "for the rest", what ever that means. I haven't found where the 09' codes cover this. It appears that many municipalities have ditched the 06' code, because it was unrealistic with the amount of anchor bolt spacing and such. But back to my point: no matter how many anchor bolts you put in a sill that has a parallel joist running on top of it, if you don't put any blocking connecting the sill to the deck, there is really no support. If the basement wall wants to push in, it would just hinge the joist and rim board on top of it.

Now enter in floor trusses, which may be 16, 18, or 20" or more in depth. Who's going to "solid block" the floor trusses, and how? I think diagonals connecting the bottom chord of the first truss to the top chord of the second truss along with the lateral strong-backs located on the bottom of the webs is the way to go.

2009 irc:
http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_4_section.htm?bu2=undefined

2006 irc:
http://publicecodes.citation.com/icod/irc/2006f2/icod_irc_2006f2_4_sec004.htm?bu=IC-P-2006-000002&bu2=IC-P-2006-000019

Posted By jeepster on 27 Jun 2011 08:59 AM

...Arkie, is there a reason for the pvc? Wouldn't using the foam as a form for the grout work?

The PVC collar was just suggested as a way to positively contain the grout.  If you can cut a clean hole in the foam around the anchor bolt, that should work fine also.

This is a topic of significant discussion in engineering circles. There are so many variables in it, one can't give an answer that will fit all situations. But for many basementswith 7-8 ft high walls, secure attachment of the floor to the top of the wall is sufficient. The type of soil will obviously play a role.

why would you install a ledger, remove it and then drill and epoxy? What not cut out a area of foam behind the anchor bolt locations, install the anchor bolts too the ledger, screw the ledger to the webs, then pour?

Posted By lzerarc on 28 Jun 2011 04:32 PM
why would you install a ledger, remove it and then drill and epoxy? What not cut out a area of foam behind the anchor bolt locations, install the anchor bolts too the ledger, screw the ledger to the webs, then pour?

You do try and do that, but sometimes things get overlooked, omitted and reinstated after the fact so solutions need to be found and addressed. As a matter of fact just today we started a repair (so to speak) where the deck was eliminated on the back of the house and the owner came back 2 months after we were done asking for it to be reinstalled. So we removed 8" sections of foam every 16" installed 2 5/8" thick wood blocks, covered with the ledger board, drilled through the wood into the concrete by 5", epoxyied 5/8" threaded rod and once set snugged the nuts, good as new and you wouldn't know how we did this, but I know the deck is secured properly to the wall and is not going to come off