How to build a foundation on two levels?

I'm planing on building an addition but to start out I want to do an "as is drawing" as a place to start. My house is on a slope and has two levels with the garage on the bottom and the house above that. The house is larger than the garage and spreads west above grade of the slope. So I have essentially a day light basement for the garage. I can't get started on how to add the second floor and add a foundation to the second floor above and to the side of the garage. The garage has a concrete retaining wall on the west side that I can't seem to get set on the foundation either. Please see attachment.

Draw your main living area with the floor height @ "0". Derive your foundation with the wall height set @ the actual ceiling height of the garage. (try 96")


Bisect the foundation plan with a foundation wall. Set the stem wall height on the side that is not the garage to 36" (or whatever your crawl space is). Set the room type for the garage as a garage. Add garage door. You end up like the attached.

jon

Would this be the same process for designing our remodel of our split-level ranch home? Primary living area is above garage/family room floor and about 3' wider than ground floor. Length of both floors are the same. We're using HDPro, v10. Thanks.

Split level is a bit different. On the 1st floor, I would set the lower portion as your "0" floor and then offset the upper @ whatever the true offset is. (below the offset is 51") then, derive your foundation.

The image below is from a circa 1952 split rancher remodel/rebuild. Foundation and roof line are completely new.

Rear elevation shows offset better. Offset is accomplished on the same floor in HD.

jon