when You do Your ICF building what size of forms do You use. Do you very the size or do you keep the size the same

what size do You use for

Basement only

   and for

Basement with above grade

It depends. You can generally use 6" core ICF for basement or basement plus one floor above.

I opted to go with 8" core ICF walls in my basement with 6" ICF for the floor above. The reasons I decide to go with 8" is additional strength to hold back the ~7' of clay backfill along a 62' straight wall and also to provide a lip on the inside of the wall to allow me to hang my open web floor trusses (requires use of a taper top form on the 8" basement wall and modification of the 6" ICF at the junction to provide sufficient support for the floor trusses).

i used 8 inch in basement and 4 1/4 inch first floor just so i could put floor joist on top of concrete

I agree with arkie and frankrizzo -- typically 8" and up for below grade - although i've seen 8 story hotels hotels using 6" only. Generally, if backfilling is involved 8" is prefereable. Regards.

6" for most applications. 8"to carry a concrete floor system or very high ceilings and high clay back-fill.

Did not catch what part of the country you are talknig about. I'm a custom home builder who has built basements with CMU's, poured wall, and now planning my own home this summer using ICF's. Our family has also been in the ready-mix supply business for some 60 years now. All of the above is correct, but your basement walls should be sized by an engineer with knowledge of your soil conditions. I have done 8" poured walls in "Elnora" sandy loam (clay, sand and shale) at 13 course which engineered out to an 8 " wall with #4 vertical rebar at 40" on center along with Ohio's standard 3, horizontal rebar placement. Knowing a little about concrete I used a maximum slag ratio to cement of 30%. Although I used to place 3500psi concrete in the basement walls, I have since discovered that the added cement content hinders consolidation and is not needed as 3000psi actually cures out stronger than designed because of the nature of the ICF form. Have seen many cracks at corners of competitors homes and will recomend using 10" core at outside corner walls as viewed from inside the basement. The reversed forces put on these areas can be overlooked in an engineers computations. My own home will have 10" core at the basement and reduced to 6" to created a ledge for the first floor deck as mentioned above. Looking into using steel fiber in place of rebar for strength. The benefit is reported to be straight corners as bent rebar often distorts corners in practice. Also, your dump yime is significantly reduced and consolidation is much less of an issue. Also reduces the chance of blowout from vibrating heads hitting forms. Good luck on your project.

One quick note: I'm fine with fiber mesh -- If you are careful that your steel is bent to 90 degrees you won't have any issue. Most pre-bent 90s (that i've actually checked) s bent to a little less than 90. Regards.

Why would you stop going vertical with an ICF that produces a 8" core? If it was good enough below grade, wouldn't it be good enough the higher you go? Doesn't a thinner wall reduce the performances. Isn't the vertical limitations, a decision for engineering?

Posted By BWerks on 09 Mar 2010 11:13 PM
Why would you stop going vertical with an ICF that produces a 8" core? If it was good enough below grade, wouldn't it be good enough the higher you go? Doesn't a thinner wall reduce the performances. Isn't the vertical limitations, a decision for engineering?

Concrete is expensive.  A 6" core wall uses ~25% less concrete than an 8" core wall.   A 6" core wall provides more than sufficient strength for above grade walls.  From an insulation or thermal mass standpoint, there isn't any significant advantage to an 8" wall vs a 6" wall.  So, it comes down to the cost of the concrete and the 2" of extra interior space around the inside perimeter of the home.

What if the 8" wall still used 5% less that the 6" wall? If the thickness of the wall doesn't matter then why do engineers always concern themselves with that number?

We just finished an engineered project in Akron, Ohio that used the 8" Weblok ICF's. Site was on the side of a hill, and had 19 foot tall walls in some sections and even had another wall with 13 foot of unbalanced fill and still supported the 14" Lite-Deck floor system ( 104,000lbs of concrete + 3 suburbans). All this was completedl following the steel schedule (nothing unreasonable) that was prescribed.

The professionally engineered solution replaced a 12" poured wall with pre-cast concrete floor system. The customer recognized major savings before he even taking into the account savings he would have not having to insulate and fur out the wall of his living space.

If you knew what he was putting in this "garage," you would have to give him the ultimate "Man Cave" award.

does this happen to be for Lebron......hmmmm.....

Posted By BWerks on 10 Mar 2010 06:26 PM
What if the 8" wall still used 5% less that the 6" wall? If the thickness of the wall doesn't matter then why do engineers always concern themselves with that number?

huh?

All of the engineering tables I use have overlap for a given load, wall height and back-fill. So where you can use either the 6" and 8", they are equally strong.

A Professional Engineers review of a project in the most cost effective expense for any ICF Builders. Their "Stamp" is invaluable and the cheapest liability insurance around.

Tables are available and are effective for estimating a project, but why would a builder builder accept that level of liability....a P.E.'s review and stamp of approval to important.

Why would you use a 6" wall that might work, when you can have a 8" wall for the same price?

What if you could have the 8" Wall and still be less expensive?