Was recently called to assist a builder on a 4000sq/ft rectangular home. The footings were poured with #5 turnups @2'oc. BO approved footings. A three foot tall stemwall was built with the same turnurps and approved. The floor system was built, approved, covered w/ 3/4 Advantech and the walls were built to the second floor and braced for the next pour inspection. The BO then realized the area was a D1 earthquake zone and the rebar needed to be 18" oc rather than the 24". The builder is meeting with an engineer in the morning to discuss options. Does anyone have any ideas on a remedy other than to have done it right the first time?

Posted By scicf on 03 Jun 2012 08:21 PM
Was recently called to assist a builder on a 4000sq/ft rectangular home. The footings were poured with #5 turnups @2'oc. BO approved footings. A three foot tall stemwall was built with the same turnurps and approved. The floor system was built, approved, covered w/ 3/4 Advantech and the walls were built to the second floor and braced for the next pour inspection. The BO then realized the area was a D1 earthquake zone and the rebar needed to be 18" oc rather than the 24". The builder is meeting with an engineer in the morning to discuss options. Does anyone have any ideas on a remedy other than to have done it right the first time?

Here's my thoughts coming from the experience of one ICF house, my own, 22 years of quality assurance enforcing contract and code requirements, and being an engineer.

First, you'll have a tough time laying the responsibility on the BO. It is not his job to make sure the job is done correctly. His job is to verify. The builder is supposed to know the codes and follow them. This ain't necessarily the way it is in the real world, but real world practices don't excuse failure to follow codes, especially if you are in front of a judge. So, whatever the BO is willing to go along with, accept it and don't force the issue.

Since the walls aren't poured it is practical, and possible, regardless of cost, to disassemble the blocks and put in more rebar. How much rebar was exposed about the stem wall? One idea that comes to me is to take down the wall and attach, by welding or with wire, a horizontal rebar to the stub ups of the stem wall rebar. Then attach a vertical rebar, with an L bend at the bottom end, at 18" spacing to the horizontal bar by wire. Or make a U shape rebar segment with the verticals 18" apart and the bottom of the U attached to the horizontal rebar.

My thinking is that in the event of an earthquake most of the building movement and tendency to come apart will be in the upper areas of the walls, more so than in the footer or stem wall. By solidly connecting the upper rebar at 18" spacing to the lower rebar at 24" spacing you should end up with an overall wall strength on par with rebar at 18" from the footer up.

Another thought. How deep into a D1 zone is the house? Is it near the demarcation between D1 & D2? If so, then you may try arguing that the zone boundaries are somewhat nebulous and so maybe the house ought to be allowed to follow the D2 requirement.

Without doing some looking up I'm thinking D2 is less than D1. If that's not correct, then use whatever the designation is for the zone less earthquake prone than D1.

See if you can get an engineer to approve Helix. It's not a earthquake reinforcing but used with the rebar would do the job as well as going with a higher psi concrete like a 4000.  Speaking of engineer , in NY you can't build anything over 1400 ft without one.

Met with the engineer this morning and got a lot of good ideas. He's working on the most efficient way to correct this and may take a few days of running numbers. Dmaceld- one of the things he is considering is introducing a #5 bar with a slight bend at the bottom to angle over twelve inches to the stubup. This isn't the optimal solution, but I'm willing to do whatever he recommends. It would put verticals @12" oc which would be well within code. He also stated that the fact it is in a stem wall (lower to the ground) it didn't bother him as much as it would if it were higher.

She's coming down---if the rain ever stops.

I am 1/2 mile away from the San Andreas fault in Southern California and my engineer (and county approved plans) said I have to have #4 rebar every 14" on center. I ended up using #4 in the stemwall but #5 in the ICF walls. My engineer claims that with ICF's and earthquakes it's not about wall thickness it's about the rebar you use. So I would say the OC distance of your vertical rebar is important. With horizontal rebar and 4" core walls you'll want to use #4 rebar. Thicker rebar will be too thick for 4" core walls.

Now about your case, before you freak out, you need to realize something about earthquakes and ICF's. You'll get alot of opinions on this forum and in the industry from people who have very little or nothing to support their supposed facts. Take for instance your BO who claims you are in a D1 earthquake zone. Ask him to prove it and you'll find that you will get a wishy-washy answer. Don't just take his word for it. Have him show you where he got the data and have him show you the data. dmaceld claims there are lines of demarcation between D1 and D2. Earthquakes are chaos. As such they don't adhere to lines of demarcation. The experts know this and will avoid providing you with any kind of data which you can then use against them in a court of law. Take for instance the Northridge earthquake. A fault existed underneath the ground and nobody knew about it. How can you adequately map something you don't know for certain exists? The experts cover their behinds and only offer extremely general and wide ranging specifications. When you zoom in to view your particular location on their maps and documents you'll notice the zoom button doesn't let you get that close.

That said you would do well to look for the study done in California. There was some study done on earthquakes and ICF's recently. Word is that the state of California now mandates using 4" core ICF walls in all construction done for the state. My construction project, link below, will act as a guinea pig project for the Oztec rebar shaker. The problem with 4" core walls is that a vibrator does not fit. You could use a 3/4" vibrator but that will barely fit. If the rebar shaker works well on my project the builder who is working with me will use it on the state of California project he will do next.

http://tj.jjt.partyconnect.me/construction/walls/

Now, getting back to your question. If you can access the stemwall use a rotary hammer to drill holes half way in between the 2' OC rebars. That would make it 12" OC. So then you have half the rebars extended all the way down the stemwall and the other half extending as far as the rotary hammer can reach. Of course that's just my suggestion. You may need to figure out what works with your building inspector.

Jackta--I'm all for fighting the good fight but even John Wayne won't take on the government. It was a mistake that fifty miles away wouldn't matter but in this case the floor would rot and the rebar would rust away before this case was settled. Code for D1 is #5 verticals @ 18" or #4 @ 12". #5 horizontals ONLY. I'm just going to fill in with #4 epoxied into the stem wall @12". Shoulda learned to read!

Posted By jacktca on 05 Jun 2012 02:33 PM

That said you would do well to look for the study done in California. There was some study done on earthquakes and ICF's recently. Word is that the state of California now mandates using 4" core ICF walls in all construction done for the state. My construction project, link below, will act as a guinea pig project for the Oztec rebar shaker. The problem with 4" core walls is that a vibrator does not fit. You could use a 3/4" vibrator but that will barely fit. If the rebar shaker works well on my project the builder who is working with me will use it on the state of California project he will do next.

Why is California going towards the 4" ICF and not the 6" ICF?

This is hearsay.   The local ICF builder who is consulting on my project told me that there was some study done regarding ICF's and earthquakes.   As a result projects done for the state of California now require 4" core to be used.    I have a feeling that the study might have concluded the same thing that my engineer told me.   He claimed that rebar not wall thickness is the deciding factor in earthquake safety.   The reason I say this is because my ICF consultant said that it is a competitive bidding issue with the State of California.   They don't want to pay for thicker walls if they can't justify it.   Something like that.    Ironically he is a distributor for an ICF company that company has a local manufacturing plant but they only make 6" core ICF's.   So the 4" core ICF's have to be shipped in from Idaho or some far away place like that.   He will also have to buy an Oztec rebar shaker because a vibrator won't fit into 4" core walls easily.   What the state of California saves on concrete they will lose on shipping and re-tooling.  

Posted By jacktca on 07 Jun 2012 02:48 PM
He claimed that rebar not wall thickness is the deciding factor in earthquake safety.  

   Ironically he is a distributor for an ICF company that company has a local manufacturing plant but they only make 6" core ICF's.   So the 4" core ICF's have to be shipped in from Idaho or some far away place like that.   He will also have to buy an Oztec rebar shaker because a vibrator won't fit into 4" core walls easily.   What the state of California saves on concrete they will lose on shipping and re-tooling.  

Rebar is key but the problem with a 4" core is that fitting the rebar in properly and having the concrete consolidate properly in a 4" core, it's just too tight.

Nudura ICF's fold upon themselves so shipping a 4" or 6" core makes no difference as the form closes upon itself.

That's where the Oztec rebar shaker comes in.   Hopefully.  We'll see if it works.   I'll follow up with news and opinions on that here on this forum.    As far as fitting the rebar.  I inserted and tied the rebar for my 4" core project myself and I didn't have any problems accessing the rebar and tieing it.  The only problem I did have was dropping something into the blocks.   With 4" core it can be an expletive to remove!   What I would have a problem with is cutting blocks that fold upon themselves.   Nudura might be great if cost is no object.   Build the structure without any openings first, then cut out the doors and windows with a sawzall.    I suppose what you spend on extra blocks you'll save on shipping costs.   

Becafeful with what the inspector is telling you, his answer to you is based off what is written in the code, and the code is written to cover more than one application and not specific to your job. If you have a good engineer he will actually run the numbers on your job based on all conditions that are job specific. You would be amazed when this is done the savings that can be realized.

Promised a follow up regarding the Oztec rebar shaker after the pour. My pour is done today!!! Oh Yeah!!! Success!

According to the ICF expert who was helping me the rebar shaker passed the test. So if you have 4" core ICF blocks find someone who has one of these to help you with the pour.

Thicker walls mean heavier walls.
Heavier walls mean lots of rebar.
California is right.
I lived 7.5 earthquake for 45 seconds.
I know what heavy results in.
I have 6" walls with 15m o.c. 8.
Thus using strong mpa is not a solution.
Use designed rebar.
Thus the rebar is chapest part of the project.