foundation

Question:
what does it mean when it is said 18" below grade with a 6" stoop?

Answer:
Hi, Thanks for visiting

Without a little more information about the detail or where the note came from, I can't be really sure what the designer/engineer is intended to do.

Assuming that the note came from a foundation detail, I can only guess that it means 18 inches below finished grade with a 6 inches projection above finished grade for a total foundation height of 24 inches. That is if the detail is shown with a little projection above grade.

If the detail is that of concrete step foundation, than the foundation is slanted such that the top of foundation is always 6 inches above finished grade for the steps to sit on.

Hope this helps
Tonga