adding grid lines to existing

[arkitek2ss]

Im sure this has happened before.  adding an addition onto a building.  existing grid starts in the lower left (A, B, etc up the page and 1, 2, etc. left to right).  new addition starts between D8 and E8 and goes to the lower right.  i'm good with vertical grids (continuation 9, 10, etc.) but how would someone continue the labeling below/prior to grid A?

[hmunsell]

-A, -B, -C, .... 

seriously though... that's a good one. i asked my most senior architect and he looked at me and said "What...". after i reexplained it, he then recommended AA, BB, CC, etc...

[arkitek2ss]

thats what I did.  anything below A went to AA, BB, etc.  anything above A went to #.2 i.e. grid fell between B and C, labeled it B.#, etc.

thank you.

[hmunsell]

sounds good....