The main downsides of using Helix include the additional material cost, finding an engineer who can/will design with it and having inspectors who will approve it (having the engineering stamp on the drawings helps with this). You also need to verify that the correct amount Helix gets added to the concrete mix and that the mix gets adequately mixed prior to the pour. There have been issues and actual lawsuits associated with this. You will likely still need to use rebar for the door and window lintels unless you have the capability to pour different Helix density mixes real time using dye to color code where this was accomplished. Helix is a great product and construction option, but it is still relatively new and not yet widely used.

Oh, one more thing came to mind... Verify if the ICF product that you will be using can be poured without horizontal rebar being placed in each course. Some ICF products require this rebar to provide adequate support during the pour and some ICF products may require tying the blocks together or providing additional bracing/strapping if this rebar is not placed.

Sailawayrb, It's true that the rebar will distribute loads across ties etc. but I've used it a number of times with Nudura over the years and never seen this to be a problem. I think the biggest issue is weighing additional costs against the rebar and additional labor costs -- a point you also made above.
Regards, Cameron

Sailawayrb, It's true that the rebar will distribute loads across ties etc. but I've used it a number of times with Nudura over the years and never seen this to be a problem. I think the biggest issue is weighing additional costs against the rebar and additional labor costs -- a point you also made above.
Regards, Cameron

I should add that you need to really mix well to ensure proper distribution and no clumps.

Yes, we have used BuildBlock, Nudura and TF Systems (vertical ICF) without any issue too. However, I understand some other ICF products are more susceptible to block floating and movement, and hence my cautionary statement to first verify with the manufacturer of the ICF product that will be used. Yes, I also mentioned the proper measuring and mixing requirement too, but you really can’t mention that too much as it is very critical. It was the Pensmore Mansion (72,000 sf) TF Systems project that had the most notable lawsuit associated with this issue!

I think Pensmore was an intentional act, correct? The concrete supplier was shorting the Helix and using it on different jobs. Do you know if any other issues that people have had? I would think that just tossing the boxes in the trucks before pouring without concerning yourself with clumps would lead to some problems. I think the preferred method is to add Helix to the water at the plant before remaining materials are added, it would be nice if I could get the concrete plant to do that.

I assume if I have Helix specd that I would end up needing conventional rebar around openings and some vertical bar as well.

As for the block I'm using, its between Fox Blocks and BuildBlock, not sure if either of those require horizontal bar to keep things straight. Fox has the HV Clips which likely help

We have used BuildBlock and it doesn't use or need any clips or ties whatsoever. I don’t know about Fox. Yes, as I mentioned previously, you will still need rebar for door and window lintels unless you can pour a higher density Helix mix. Again, the engineering will define the rebar and Helix requirements. The Helix is slowly put into the concrete truck per their instructions. Yes, it was alleged Pensmore was intentional and there have been other intentional and unintentional cases of shorting or improperly mixing the Helix. Bottom line, you should have someone you trust at the concrete plant to verify that the Helix is applied per the engineering and is properly mixed.

Rebar is not that hard.....

Agreed, placing the horizontal and vertical rebar in ICF is relatively easy and foolproof. Only the lintels are somewhat complicated. We typically always do the rebar and we only use the Helix to provide additional strength for seismic requirements when needed. And while being a Texas bred gal and accustomed to hard work, I have managed to get tennis elbow a couple times from bending, cutting and placing the rebar which is repetitive work.

I have been using Helix since it came out, and really like it. My preference is to use 5 lbs./yd to supplement the PCA-100 rebar schedule, but we also regularly use it as a replacement in 4" core walls. In my experience it usually makes financial sense as a complete replacement only when the rebar schedule calls for horizontal bar every course. In this case the labor savings really stacks up (pun intended)!

Jake, Im guessing you get a very strong wall using both bar and helix. Do they engineer any of the bar out of the design when you use 5lb/yd dose?

I don't try to reduce rebar at a 5 lb dosage. I bill that as a supplement, and charge accordingly.

To try to minimize installed cost is another thing. In my opinion, that would mean suing Helix at a dosage that completely replaces horizontal rebar, then installing only what vertical was still needed. But that's just my experience.

Helix Dosage Calculator

But you still need to have a structural engineer PE stamp the drawing...

We don't need that for the 5lb supplement provided we follow the PCA-100. If you are speaking of the replacement, maybe. Helix provides engineering. Some inspectors will require a third party, some will not.

The calculator is for replacing rebar with Helix to achieve the same load capacity. Engineers design a wall to handle some given load scenario. They don’t just throw some amount of Helix into the concrete mix like offering sauteed mushrooms on your steak for slightly additional cost. If you are just doing a simple prescriptive design/build (PCA-100), you don’t need any engineering and you don’t need any Helix either...your money would be better spent on more insulation, etc. If you use Helix to replace rebar or satisfy some additional load scenario requirement (e.g., seismic), you are NOT doing a prescriptive design/build and you need to have a structural engineer PE stamp the drawing.