In trying to simplify the footprint, our house design now has a 48' long wall with 6 windows (two 3'w x 4'h, two 3'w x 1.5'h, and two 2'w x 6'h).    The following extract from Section 6-1 in the Logix Design Manual says

"...Tables 3A and 3B provides reinforcement tables for LOGIX walls used above-grade.

Building limitations used to develop Tables 2A to 2D, and Tables 3A and 3B include:

Building perimeter = 80 ft max x 40 ft max

Roof clear span = 40 ft max

Floor clear span = 32 ft max

Number of stories above grade = 2 max ..." 


The long side of our home is less than 80LF, but there is the 48LF shorter side.  Planning on using 6.25" forms.  Walls would be 12ft from top of footing to top of wall.  Above grade section of wall will be 9'8".  Slab on grade. 

1.  Do I need to have the 48LF wall engineered for rebar vice using the prescriptive tables? 

2.  What is the difference between the Roof and Floor clear spans?

Farmboy, the prescriptive method is a guideline for your engineer he may or may not choose to stay with it depending on many variables. Show it to an engineer. I didn't follow what you were asking about spans? Regards

Look at the International Residential Code and the PCA's Prescriptive method for using ICFs in residential construction. see how your building fits with those.

1. I am not sure what Logix means, I could not find it in my SEP 14/06 version.

2. The unsupported span of the floor or roof system.

Since the ICF companies have provided a blanket engineers stamp on their tables and are not job specific they have had to provide restrictions. It's strictly a liability thing.

This is why you see the 40x80 footprint size, as well as the span sizes. These can be exceeded provided you have an independent engineer who is job specific review and design your project

80x40 is very limiting. Check the IRC or prescriptive method.

this is from IRC 2009

R611.2 Applicability limits. The provisions of this section
shall apply to the construction of exterior concrete walls for
buildings not greater than 60 feet (18 288 mm) in plan dimensions,
floors with clear spans not greater than 32 feet (9754
mm) and roofs with clear spans not greater than 40 feet (12 192
mm). Buildings shall not exceed 35 feet (10 668 mm) in mean
roof height or two stories in height above-grade. Floor/ceiling
dead loads shall not exceed 10 pounds per square foot (479 Pa),
roof/ceiling dead loads shall not exceed 15 pounds per square
foot (718 Pa) and attic live loads shall not exceed 20 pounds per
square foot (958 Pa). Roof overhangs shall not exceed 2 feet
(610 mm) of horizontal projection beyond the exteriorwall and
the dead load of the overhangs shall not exceed 8 pounds per
square foot (383 Pa).

Prescriptive methods, whether ICF, wood, or whatever, are defined by a set of parameters selected as an "envelope" for the prescribed methods. That is, they come up with a set of commonly used applications and set about giving guidelines, design tables, span lengths, or whatever the output is. The "envelope" then is the limits at which the tables or methods are starting to fall apart because some parameter is introduced whereby the application no longer works.
In the case of the ICF limitations, I think it is based upon the assumption that the joists run paralell to that side, and bracing it may require more scrutiny. I'd have to check the definition to know for sure, though. BTW, the limits are very VERY often overlooked with stick frame, which is one of the reasons so many of them get distressed.
An engineer should be able to look at the non-prescriptive issues and let the rest fall into place with prescriptive methods.