Layer function priorities cannot access from the Core Boundary to Finish Face

[aireq]

I'm trying to make a Wall Family for an exterior wall. The walls has the following layers

CMU -7 5/8
Air - 1/2
Stud - 3 5/8
Gyp - 5/8

I want to be able to assign a wall footing to the wall and have the footing center on the cmu wall rather then the entire wall. So I am trying to make the core layer the CMU only. I created the layers as shown bellow with the following functions set.

1 CORE BOUNDARY
2 CMU -7 5/8 Structure[1]
3 CORE BOUNDARY
4 Air - 1/2 Thermal/Air Layer [3]
5 Stud - 3 5/8 Structure [1]
6 Gyp - 5/8 Finish 1 [4]

However, when I press OK I get the following error:

Error: Row 4: Layer function priorities cannot access from the Core Boundary to Finish Face

Is there a way to setup these wall layers so that a wall footing will center on the CMU only rather then the entire wall?

[ChrisGamble]

I get the same issue in 2019. I have to make Air a substrate. Dont understand why. 

[kadmonkee]

in Revit 2020

it may be function assigned the material should not matter

be sure to check Structural Material on the right side for Structure 1

i got zero errors