My house plans are for a full basement, 8' first floor and approx. 4' knee-wall 2nd floor. The house will get a 6" stone veneer.

I planned on using 6 icf (arxx 61/4 core). My arxx rep tells me that this is all I need but I'm also being told by a local builder that uses icf that I need 8".

I normally tend to overbuild and the 6" forms with all the reinforcement and slow cure seemed to fit this bill. Should I be considering 8"? The arxx rep. claimed it would be a waste of concrete for me.

8" is common for below grade but what your rep says or what i say or others say on this forum is not really important. You should have an engineer review your plans. Regards.

The 6" should be fine. If you are worried, use the 8" for the basement, and 6's above grade.

Thanks for the replies. In New York I'm not required to have my wall plans stamped when using icf's (unless local codes enforcement decides that they want to require it), but it wouldn't hurt to have them reviewed by an engineer. The Arxx rep. I'm communicating with said that soil type is the determining factor. Mine being well drained cohesionless soil (sand and gravel), apparently 6" is appropriate.

There are actually a lot of places in the US that don't require stamped drawings. Doesn't mean it's not a good idea, or that what you end up using will be all right because it's not required. If you have some good prescriptive design tables and reliable soil information telling you one way or another, go with it. Otherwise get a professional to do his magic.

I have been an ARXX distributor and builder since 1998. ARXX now has a structural engineer on staff. It doesn't mean you can get a "stamp" in every state, but you should ask your ARXX rep to contact Coburg (ARXX homebase) to get you an answer.
Bruce M