Any input on using 4" forms 9' tall for house exterior walls.

Mike,  A few years ago a highly experienced concrete guy said he'd have no problem building his home with 4" ICF block.

Per the Logix Engineering Analysis Report for ICF construction using 60 grade rebar, you can build 9' above grade walls able to withstand 130 mph winds with vertical #4 rebar spaced 18" o.c..  See page 18 or so.

http://www.logixicf.com/media/library/product_manual/Section%206%2060ksi%200526094a1c47ef6796e.pdf

Dave

I've personally done 3 without a hitch. There is no problem at all. If you think about it, 4" of concrete is much stronger than a 2x4 every 16".

My opinion is though, for a small amount more (if any) you could have a stronger and quieter house with 6".

Check code where you live. In VT & NH, exterior walls must be at least R-19, and while stated performance value of a 4" ICF might be higher than "19", some municipalities go by the measurement of materials.
B Merritt

the r-value of concrete is about 0.08/inch. that means that if you kick it up from 4" to 6" wall you are only gianing an additional R-0.16.

Bruce, when the OP referred to 4" ICF forms, I'm sure he was referring to the concrete core thickness, not the foam thickness.

Most ICF forms have foam side panels from 2" to 2.5" thick (some thicker for high R values). All of the 2" thick foam ICF forms that I have seen use Type IX EPS which has an R value of 4.2 R/inch @ 75F. At 25F this same EPS has an R value of 4.8 R/inch. See the following link. In a cold climate, you might see 2" x 4.2 R/inch on the inside foam and 2" x 4.8 R/inch for the outer foam panel. This results in a total R value for the foam of ~18. The total R value for the wall would be somewhat higher considering the small R contribution from the concrete, sheathing, wallboard, etc.

Most ICF blocks use 2.5" thick Type II EPS foam which has a slightly lower R value of 4.0 R/inch @ 75F and 4.6 R/inch @ 25F. In a cold climate, you might see 2.5" x 4.0 R/inch on the inside foam and 2.5" x 4.6 R/inch for the outer foam panel. This results in a total R value for the foam of ~21.5. Even using the lower 4.0 R/inch at 75F, you are still looking at a minimum of R20 for 5" of Type II EPS. The total R value for the wall would be somewhat higher considering the small R contribution from the concrete, sheathing, wallboard, etc.

http://benchmarkfoam.com/eps-properties/

Thank you for the imput so far and yes I was refering to the core thickness of concrete.
My question may have been a little vag. just wondering about streingth,energy savings and if any cost saving by using that core thickness. and maybe how much trouble they are to pour?

Strength.. 4" of steel reinforced concrete is mighty sturdy.  Reference the Logix engineering reference I posted above or any of the other brands that have manuals online.  Obviously, an extra 2" of concrete would provide more strength which one should consider depending on what forces of nature you expect or structural loads on your wall.  I live in Kansas so high winds and tornado potential were important considerations in selecting 6" walls for our future home's 9' and 14' walls.  But for our 6.7' high pumphouse walls on a 48 SF footprint, 4" ICF walls were satisfactory.

Energy Savings.. addressed by previous posts.

Cost Savings.. I found the 4" forms were almost as much as the 6.25" forms.  I did use 2.1 CY concrete for the 4" walls, but 6" walls would have used another 1.2 CY or about $100.  You might consider that cost could be offset by the extra care/labor in bracing the 4" wall and tying rebar overlaps on top rather than side by side.  We didn't want the aggregate to have a chance of clogging up the gap if rebar was placed side by side.

Pour.. Once we had a 6" slump using 3/8" aggregate the concrete flowed rather well and no swelling or blowouts encountered.  Since the chute wasn't high enough to drop the mud directly into the wall, we (4 people) did a bucket brigade using 3.5 gallons kitty litter buckets.  We half-filled the buckets (a manageable weight) in the back of a pickup (tarped the bed) which got us close to the scaffold height.  We poured three lifts of a little over 2 ft each due to air temp in low 30's with no problems.  We did use a 1 HP Oztec vibrator with a 1" pencil head to consolidate the intially thicker concrete under the door buck without any problems.  Just didn't linger.  Important to get the correct slump.  Whether pouring out of a chute, buckets or a pump hose don't pour into the same spot continously, keep the stream moving even if slightly.  We tried to follow the manufacturer's installation guide to minimize tempting fate.

arkie6 is right about most forms being identified by their concrete core. ARXX brand 4 inch forms have 4 inches of concrete and 2 panels of 2 inches each side. Total width, 8 inches. Used a lot for party walls. Definately better than a 2 x 4 stickbuilt wall.
An ARXX 6 inch form is 11 1/2 inches, outside to outside. Concrete core is 6 1/4, and each panel, or side, is 2 5/8 inches each, the depth of an electrical box.
Have worked with many different sizes and find 4 inch very narrow and difficult to get ones hands inside to work comfortably.
Bruce M.

Good point about the narrow working space.  Luckily I have small hands, but I can imagine it would be  hard for some folks to gain access to zip tie blocks or tie rebar.   That's is my wife's hand in the photo!

Note the Logix block has 2-3/4" foam side so 5-1/2" of foam provides estimated R-22. 

I agree with the majority, we have done several 4" structures , but for the price difference you gain so much more going to a 6" core.Logixs web configuration allows the concrete to flow if your slup and mix are right.

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TB MACS/ ICF CONTRACTOR
BUILDING THE CAROLINAS ONE BLOCK AT A TIME!

4" would be fine, much stronger than lightweight framing, but I would use 6". Look at the engineering on lintels and how much you are limited to with 4". For the right applications I use 4", but those are few and far between.

Built numerous homes in Florida and almost used 4" exclusively except where wall heights started to run 16' +.  Had a fabulous PE that "got" the whole ICF thing. Hunt down Chris Kathe PE and your life will be simple.

Have you done 4" in TF Vertical?  It would appear that (being able to slide up the panels) restricted space shouldn't be an issue.  Your thoughts?