ICF ReBar Placement - "Vertical" tied to "Horizontal"?
Last Post 25 Jul 2013 10:59 AM by d'techguy. 35 Replies.
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Roger RUser is Offline
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29 Jun 2013 06:42 PM
I am having an addition designed and we will use Quad-Lock (probably) for the walls. I have talked to several ICF contractors as well as several factory reps, about the use of rebar in the walls. I understand how to calculate rebar both horizontal & vertical in a typical wood formed concrete wall - using 1/2" bar every 12" horizontally, and 1/2 bar every 6 to 12" vertically. All bar is TIED at the horizontal/vertical intersection. This I understand very well, and have done a number of times. I am confused how all (most?) of these ICF manufacturers say " snap the horizontal bars into the plastic clips and just drop the verticals down prior to filling with concrete". This is so far from my reality of a safe and secure wall that I am sure I am missing something. Can someone please jump in here and explain this to me? If those vertical rebars are just floating and not tied onto every horizontal, I do not believe the wall is a quality, earthquake proof wall. I can not think of one commercial job where every bar is not tied. This was my main reason to look hard at Quad-Lock, as you can build the blocks from side to side "after" building the "proper" rebar wall. So, there's my dilemma and I would enjoy a conversation on the subject. Thanks.
jdebreeUser is Offline
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30 Jun 2013 06:58 AM
I don't see how that little wire tie is going to make the wall any stronger; I always thought they were just there to keep things in place during the pour. I tied the tops of my verticals for that reason. With most ICF, the verticals can't really go anywhere if you stagger the horizontals.
Midsouth ICFUser is Offline
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30 Jun 2013 12:40 PM
Like stated above. If you stagger the placement of the horizontal bar so there is a slot to drop the vertical bar down in, the bar will not be pushed to the foam. Rebar does not need to be tied in any way in a normal straight wall. the horizontal will rest on the plastic ties and does not need to be tied. and if the stagger is done right, the vert bar wont move back and forth, only laterally, which is fine, so after the pour while the concrete is still wet you just have to center the bar.
Ryan Gunn
Owner, Midsouth ICF Builders LLC
arkie6User is Offline
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30 Jun 2013 01:00 PM
Slip a short (~1-1/2") section of 1-1/2" diameter PVC pipe over your rebar dowels coming out of the footer, then drop your vertical rebar into this piece of PVC pipe. That holds the bottom of the vertical bar in place next to the footing dowel. Then wire tie the vertical bars to the top horizontal bar. Lift each vertical bar up ~1/2" before you tie the wire and this helps put downward load on the top of the ICF forms.

The tie wire is only there to hold the rebar in place during the pour. It performs no structural function after the concrete is cured.
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30 Jun 2013 02:37 PM
If you want a wall that is ready for a seismic event you need an engineered wall not a wall designed in a vacuum. Rebar placement is critical in these instances. But, having said that, the strength of the wall is in the rebar design, not in how they are attached to each other. Rebar tying is ONLY for the purpose of keeping bars located during pouring and consolidation. I am building a QuadLock seismic and hurricane engineered house and my engineer and I have gone over this repeatedly. Our steel design has 12" horizontal spacing to take advantage of the QuadLock spacers. The short length of PVC pipe over the rebar stub at the bottom of the wall works well for vertical bars. Just be sure to have your stubs long enough to have a "legal" splice for the diameter of bar you are using.
Roger RUser is Offline
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30 Jun 2013 04:42 PM
Thanks for all the replies.... but I just can not understand how "not tieing" the rebar can work. Every commercial job I have ever seen ties the rebar, etc, etc. Weaving it between the staggered horizontal bars is not the same as tieing them. Slipping it into a PVC sleeve is not tieing it either. When a wall moves (breaks) it can break horizontally or vertically. Never the less, it looks like Quad-Lock can satisfy my paranoia as we can build each side 'around' the rebar wall.
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30 Jun 2013 05:33 PM
Posted By Roger R on 30 Jun 2013 04:42 PM
Thanks for all the replies.... but I just can not understand how "not tying" the rebar can work. Every commercial job I have ever seen ties the rebar, etc, etc. Weaving it between the staggered horizontal bars is not the same as tying them. Slipping it into a PVC sleeve is not tying it either. When a wall moves (breaks) it can break horizontally or vertically. Never the less, it looks like Quad-Lock can satisfy my paranoia as we can build each side 'around' the rebar wall.


Roger - the only time bar has to be tied or restrained is if less than an inch of concrete is between them. In other word, on a splice the developed length of overlap must be tie such that the concrete will hold the two together or must be space a minimum of 1 inch apart so that the concrete can completely surround each piece. As has been mentioned the wire has no strength. It is only use to position the bar for the pour. The clips in the webs already do this. The horizontal bars provide tension to prevent the wall from stretching and bowing. The verts do the same thing but both work independent of the other. There is no advantage of tying them.
Midsouth ICFUser is Offline
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30 Jun 2013 06:03 PM
I do not like to tie the bar at the top of the wall for this purpose. When I pour concrete, I like to have the top of the bar to have freedom of motion so I can wiggle the bar to help consolidate the concrete in that cell. Tieing rebar in an ICF wall is unnecessary because of the plastic "ties" that hold the horizontal bar where it needs to be. if you do not want to pay for the PVC, you can alsoput dimples in the almost hard concrete right next to the bar from the previous pour. the dimple needs to be about 3-4 inches deep to hold the bar.

Tieing the bar is only necessary when you have "freestanding" rebar systems that you form around. But in the Case of ICF, you form the wall and put rebar in as you go horizontally and when the wall is to the height desired, then you put the vert bar in.
Ryan Gunn
Owner, Midsouth ICF Builders LLC
BrucePolycreteUser is Offline
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30 Jun 2013 09:10 PM
Don't use a PVC collar. PVC is not compatible with concrete. Use a piece of metal pipe cut on a chop saw with a ferrous metal blade.
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01 Jul 2013 12:04 AM
Many of you guys are spot on: Bruce, Midsouth ICF and FBBP. However, some may be missing the "why" behind these ideas. ACI 318 Non Contact Spice states that rebar within 1/5 lap length (e.g. lap length for #4 is 40 diameters or 20 inches and #5 25 inches etc.) or 6 inches or less (if I recall correctly) is acceptable for the non-contact splice. Using this pvc idea although clever does not help the wall at all. Better to just follow the code. Regards.
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01 Jul 2013 02:25 AM
Don't they use PVC piping inside of the concrete walls for wiring and plumbing runs? Why wouldn't the concrete be compatible with PVC? They also bury PVC in concrete slabs for plumbing.

Just wondering...
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01 Jul 2013 06:20 AM
Posted By Midsouth ICF on 30 Jun 2013 06:03 PM
... When I pour concrete, I like to have the top of the bar to have freedom of motion so I can wiggle the bar to help consolidate the concrete in that cell. ..

That is fine on the first lift, but after the first lift starts to set and you start moving the vertical bars around on subsequent lifts, you risk degrading the bond between the rebar and concrete down at the bottom of the wall.
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01 Jul 2013 06:27 AM
You pour generally in one direction, this pushes the bar to the web and stops it there, the top of the bar you will push it in the same direction keeping it theoretically plumb. if you dowels are properly install you will meet the non-contact splice requirements as TexasICF pointed out. FYI, dowels coming out of the footing and vertical bar in the wall are not meant to work with each other. Each has there own function and not effect each other. Tying of steel is 'habit' from non-ICF days when it held the cage together prior to pour.
Chris Johnson - Pro ICF<br>North of 49
Roger RUser is Offline
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01 Jul 2013 10:58 AM
Posted By Chris Johnson on 01 Jul 2013 06:27 AM
Tying of steel is 'habit' from non-ICF days when it held the cage together prior to pour.


This is part of my original point. Doesn't the ICF work just like the old sheets of plywood - only now non removable EPS? In the old plywood forms, the steel cage "was the wall". Without the cage, the strength of the wall is next to zero. Without the horizontals & vertical's 'well tied' there is no cage. Without a 'well tied' cage, there is no strength or resistance to shifts, breaks or earthquakes. Why should that be any different with ICF's? I don't mean to beat a dead horse, but I am stuck on this point & possibly I am "missing something"... There are several systems available that let us 'build' around a cage, but most do not - and frankly, those systems, IMHO, don't seem to be building 'real walls'. Does anybody have an actual code, or engineering study (link) that can verify 'no cage' is now ok in walls?
Midsouth ICFUser is Offline
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01 Jul 2013 11:37 AM
If you use Fox Blocks, NuDura, Build Block, quad lock and other alike, it is impossible to build a "cage" and then the wall. Please research how to install ICF from block companies, as most leading blocks are in compliance with any and all codes. Refer to www.Foxblocks.com and or this link http://www.foxblocks.com/media/8733/Fox-Block-Installation-Checklist.pdf. I think you need to understand how to install ICF to understand why you do not need to tie the rebar together. Hope this helps.
Ryan Gunn
Owner, Midsouth ICF Builders LLC
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01 Jul 2013 11:41 AM
Posted By Roger R on 01 Jul 2013 10:58 AM
Posted By Chris Johnson on 01 Jul 2013 06:27 AM
Tying of steel is 'habit' from non-ICF days when it held the cage together prior to pour.


This is part of my original point. Doesn't the ICF work just like the old sheets of plywood - only now non removable EPS? In the old plywood forms, the steel cage "was the wall". Without the cage, the strength of the wall is next to zero. Without the horizontals & vertical's 'well tied' there is no cage. Without a 'well tied' cage, there is no strength or resistance to shifts, breaks or earthquakes. Why should that be any different with ICF's? I don't mean to beat a dead horse, but I am stuck on this point & possibly I am "missing something"... There are several systems available that let us 'build' around a cage, but most do not - and frankly, those systems, IMHO, don't seem to be building 'real walls'. Does anybody have an actual code, or engineering study (link) that can verify 'no cage' is now ok in walls?


As you say, its the cage. You are wrong when you say "without the ties there is no cage." What everyone is trying to tell you is that the icf HOLDS THE BAR IN PLACE, therefore it does not have to be tied. Tying the horts and verts together is just an easy way to hold the whole assembly in place. You would not need to tie conventional form work either if you could find some other way of keeping the bar in place.There is no correlation between the horts and verts. They each provide a separate and independent function when it come to a simple concrete wall. The wire ties provide absolutely no strength, they just hold the bars till the concrete grabs them.
Roger RUser is Offline
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01 Jul 2013 04:37 PM
Are you guys tieing your corner bars together - or are they floating too?
LbearUser is Offline
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01 Jul 2013 05:46 PM
Posted By Roger R on 01 Jul 2013 04:37 PM
Are you guys tieing your corner bars together - or are they floating too?

In an ICF block the interior plastic webs are used to secure the corner horizontal rebars which are usually bent/curved.


Posted By Roger R on 01 Jul 2013 10:58 AM

Without a 'well tied' cage, there is no strength or resistance to shifts, breaks or earthquakes.

 Does anybody have an actual code, or engineering study (link) that can verify 'no cage' is now ok in walls?

You couldn't be more wrong with your statement. It's not about the "cage being tied" that provides the strength, as if those metal twist ties are somehow holding the rebar together during earthquakes or heavy loads. Let's say those metal twist ties dissolved after the pour and cure. The wall would still be 100% built to it's engineering strength.

As mentioned, the usual metal wire rebar ties have no structural rating whatsoever. That is where you are confused and wrong in your statement that a metal twist tied cage somehow keeps the rebar together after the concrete cures. The only purpose they serve is to keep the rebar in place during the pour. Once the concrete is poured and cured, they serve no purpose. In an ICF block the plastic webs secure the horizontal rebar and the verticals are secured by the horizontal bars which are locked into place.

The metal ties you see in other concrete applications have ZERO structural ratings. It's merely holding it for the pour, once the pour is done, they have no strength or purpose. With ICF just replace the metal twist ties with the plastic webs. The ICF plastic webs serve the purpose of what the flexible metal twist ties serve. Once the concrete is cured the rebar cage is in place and working 100% full strength as it was engineered to do.

Many ICF walls are built to withstand Seismic Zone Categories B,C,D and they don't have metal twist tied rebar inside. If the rebar schedule is #4 rebar at 18" on center horizontal and #5 rebar at 16" oc vertical, that is what is placed into the wall and secured with the plastic webs in the ICF block. They pump or place the concrete into the wall, vibrate and once the concrete cures, you end up with 18" oc horizontal and 16" oc vertical rebar schedule. All engineered and that rebar cage is 100% tied to the concrete wall and provides all the tension needed.


Midsouth ICFUser is Offline
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01 Jul 2013 06:06 PM
On a normal straight wall, you do not have to tie ANY bar. NONE, NADA, ZIP. There are certain occasions where using zip ties is applicable, and I have used tie wire on very special occasions. But never, ever, have I tied rebar together for a normal wall. EVER. Ive been doing this for a while too. Please take these opinions to whoever is telling you that you must tie the rebar in an ICF wall and ask him or her what they think about these valid points. Good luck on your building process, and hopefully you have faith in what we are saying.
Ryan Gunn
Owner, Midsouth ICF Builders LLC
Roger RUser is Offline
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01 Jul 2013 07:15 PM
I appreciate all the comments very much. This 'to tie, or not to tie' question has been nagging me for some time. I'm still not quite clear how the verticals are held into place. I was at one job recently, and the contractor was just "dropping" the rebar into the empty wall... some were on the left side of the channel - some were on the right side.... some were slanted bottom left - top right & so on. How could they have made these verticals tight - in a correct place? In commercial building, "the cage is the wall", since concrete is a pretty weak material unless reinforced. I can not see 'why' in residential construction the cage would not be the wall, too....
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