Why do 1st floor ceiling heights change to default when I build the 2nd floor?

[EconBlueprints]

I drew the 1st floor of an existing structure.  Finished ceiling height on 1st floor is 109", so I set the ceiling height on the first floor to 109".

Next, I built the 2nd floor.  2nd floor ceiling height is 86" so I set the 2nd floor to 86".

As soon as I generated the 2nd floor, the first floor reverts to 97-1/8".

How do I build the second floor without it affecting the 1st floor?

Thanks,

Lane

[Joe_Carrick]

You need to set the default 2nd floor "floor height" to 109" plus the 2nd floor structure thickness.

Upper Floors govern what's below.

[EconBlueprints]

Got it, thanks.  My problem is, in the real world,  I usually build from the bottom up...foundation, first floor, 2nd floor...all the way up to the roof.  
That's what fooled me.