[PdGreen]

I've been researching ways to build an ICF home for me and my family. I am building the house myself (I am a licensed contractor with many years of experience. It's not my first build, just the first one for myself, and the first time using icf).

I've been planning on either buying or renting a bracing system. However, I called a local distributor of ICF and was talking to the young man that answered the phone. We started talking about bracing systems. He said that, since I am placing icf for more than just the basement foundation (basement, plus one or two stories above grade), that I could pour the footer, then stack the blocks, then pour the basement slab, then set the subfloor using the ledger with j-bolt approach. then, only after the subfloor is complete, would I proceed to pour the concrete into the foundation walls. If I were going to do another subfloor assembly for the 2nd story, I could repeat the process. He said I would only need to use the conventional bracing system for the final story since a properly placed subfloor assembly acts as bracing.

It seems to me - at first glance - that this could work, and here's why. The subfloor, assuming its properly attached all the way around the perimeter, would hold the walls straight at the top with 0 movement. the brand of icf I've been looking at has webbing that goes all the way to the top and bottom of each block so that there is no foam to be compressed between courses, meaning it should support the weight of the subfloor... I'm having troubles seeing any drawbacks. Perhaps the wall needs stiff backs running vertically? Perhaps I need wailers?

My questions are: 1) has anyone done it this way, and can I find out more about it published anywhere (I've looked, but have not found any info). 2) If this is simply a BAD idea, I would like to know WHY it is a bad idea.

Thanks!

 

[Logdog69]

Good morning, we just did a icf foundation and it went pretty well only had 2 blow outs hence my answer, I wouldn't think you would want to put a subfloor in place for the 2nd floor without walls being poured we had bracing in place and you have alot going on with just walls not to mention an entire separate floor sitting on empty foam walls, i would cut foam to form a ledge for 2nd floor system to sit on instead of bolts

 

[rjconstructs]

I've been researching ways to build an ICF home for me and my family. I am building the house myself (I am a licensed contractor with many years of experience. It's not my first build, just the first one for myself, and the first time using icf).

I've been planning on either buying or renting a bracing system. However, I called a local distributor of ICF and was talking to the young man that answered the phone. We started talking about bracing systems. He said that, since I am placing icf for more than just the basement foundation (basement, plus one or two stories above grade), that I could pour the footer, then stack the blocks, then pour the basement slab, then set the subfloor using the ledger with j-bolt approach. then, only after the subfloor is complete, would I proceed to pour the concrete into the foundation walls. If I were going to do another subfloor assembly for the 2nd story, I could repeat the process. He said I would only need to use the conventional bracing system for the final story since a properly placed subfloor assembly acts as bracing.

It seems to me - at first glance - that this could work, and here's why. The subfloor, assuming its properly attached all the way around the perimeter, would hold the walls straight at the top with 0 movement. the brand of icf I've been looking at has webbing that goes all the way to the top and bottom of each block so that there is no foam to be compressed between courses, meaning it should support the weight of the subfloor... I'm having troubles seeing any drawbacks. Perhaps the wall needs stiff backs running vertically? Perhaps I need wailers?

My questions are: 1) has anyone done it this way, and can I find out more about it published anywhere (I've looked, but have not found any info). 2) If this is simply a BAD idea, I would like to know WHY it is a bad idea.

Thanks!

How would you get a pump hose down the wall and a concrete vibrator?

 

[Logdog69]

Didn't need a vibrator , filled up 1/3 all the way around and continued that way.

 

[PdGreen]

Yeah, there’s definitely a lot going on with pouring icf walls. having to strap icf in all the right places makes it easy to miss one or two spots.

 

[PdGreen]

How would you get a pump hose down the wall and a concrete vibrator?

The joists are attached to the inside of the wall using joist hangers (you install a ledger first, then mount the hangers to the ledger), so the icf wall is continuous all the way up to the roof line. Which means you have full access for a pump and vibrator

 

[PdGreen]

So I got on the website of the distributor that I called. I found a picture they posted depicting the process I described above. notice the wall cavity has not been filled with concrete yet.

obviously they know a builder that does it this way. I'll have to call them back and try to get more info from them.

 

[PdGreen]

Didn't need a vibrator , filled up 1/3 all the way around and continued that way.

You always need to vibrate form work. If you do not, there is a very strong possibility that you will leave major honeycombing and even voids in the wall that cause weak points. voids are susceptible to water infiltration and structural failure. With ICF its easy for hacks to get away without vibrating, because the forms never get stripped, so nobody ever sees the problem till its past the home Warrenty stage. If im not mistaken, that's the 350 way to do it..

 

[rjconstructs]

I can see a benefit of doing it that way but I'm also a bit skeptical. I would still prefer the rim to sit on the wall and be anchored to it.

 

[Rio]

Never done them but anytime with a ledger and concrete walls the ledger is attached to the concrete with bolts, which would be the case with the ICF forms. There's no way that just the ICF itself is going to hold the floor up.

 

[PdGreen]

Never done them but anytime with a ledger and concrete walls the ledger is attached to the concrete with bolts, which would be the case with the ICF forms. There's no way that just the ICF itself is going to hold the floor up.

Ok, well let’s see then.. If I’m doing a 40x40 square house with a center carrying beam using 12” trusses and 3/4” osb, my estimation is that there would be ~2500lbs on each ledger. If I put 3 deck screws into the webbing every 16”, that comes out to roughly 30lbs per screw (dead load). According to published data from one of the leading icf manufacturers, their rated fastener shear value is over 60lbs with a safety factor of 3. Also, deck screws have a higher shear value than 30lbs

I’d have to say, I think the ICF could hold the subfloor…

Maybe I’m wrong

 

[Dirtywhiteboy]

I'd put some legs under the ledgers just in case,,,

 

[Rio]

Ok, well let’s see then.. If I’m doing a 40x40 square house with a center carrying beam using 12” trusses and 3/4” osb, my estimation is that there would be ~2500lbs on each ledger. If I put 3 deck screws into the webbing every 16”, that comes out to roughly 30lbs per screw (dead load). According to published data from one of the leading icf manufacturers, their rated fastener shear value is over 60lbs with a safety factor of 3. Also, deck screws have a higher shear value than 30lbs

I’d have to say, I think the ICF could hold the subfloor…

Maybe I’m wrong

Could be, as I mentioned never have used it so would have to do a little research but with them basically being foam it seems a little sketchy. I'm with DWB on the support from underneath.
I see where it makes sense to have the frame inside before placing the concrete because it is acting as bracing for the walls, keeping them nice and vertical. Your idea of contacting and reviewing the options with the manufacturer is the way to go, eliminate any doubt.

 

[Fourthgeneration]

Fire blocking between inhabited floors?

ICF was two big issues, tons of styrene that will out gas killer toxic smoke in even a 'small fire.

thermal mass of concrete isolated by foam on interior walls / forms...

I like to see a hybrid system that used reusable forms on the interior. and left in place insulation, with reuseable engineered stiffeners and whalers.....👍

If you must use ICF on a home/ apartment, plenty of battery back up smoke & heat alarms, and cover all foam with drywall.
and I'd pipe wiring in EMT.

 

[Snobnd]

In the first picture it shows pressure treated lumber mounted to the Doug fir rim Joyst…. Is that pressure treated lumber for a future deck? If so it needs a pressure treated ledger board or at least waterproof the Doug fir.