Building stepped foundation vs full concrete foundation

[uniblab]

Hi, I am adding a room onto my house. there is a 1 1/2 foot slope from front to back(side wall), and 8 inch slope from left to right (back wall)

[code:1]
F ---------- RIGHT
R | B
O | A
N | C
T | K
-------------------| LEFT[/code:1]
I am in the government of California, so there is potential seismic activity.
What are the advantages and disadvantages of using stepped wall vs full concrete? This is what I came up with...can anyone confirm or add? Also, if anyone has recommendations on information on actually constructing a stepped foundation, I would be interested.

Stepped Wall Pros:
Less Concrete
Easier to install vents/crawl space access hatch

Stepped Wall Cons:
Foundation is part concrete, part wood (fortunately no freezing, and minimal moisture)
Harder to build the forms/pour the concrete in steps?

Full concrete Pros:
tons of concrete = lots of compression strength?
possibly need less anchor bolts, since dont need to anchor each stepped section (cost is minimal here)


Full concrete Cons:
harder to make vent/access holes in concrete than wood
More concrete
More likely to crack because higher wall?

 

[stuart45]

You really need to speak to a local builder. California has the strictest Building Regs in the USA for foundation work. They usually have a slab on grade with no basement.
I would guess that most would go with the stepped to save concrete.

 

[uniblab]

well, I probably shouldnt even be building the addition myself...I'm a software "engineer" by trade Anyway, I drew the plans myself, and actually finagled a building permit from the city, and manually dug the trenches for the footings, so not quite ready to give up yet.

As for stepped vs full, are the pros/cons listed accurate, or are there other issues to worry about? Also, I think you are right about slab on grade/no basement...but my neighborhood lies on a (mild) slope in both directions, so that's why there is stem wall instead of slab.

 

[stuart45]

As for stepped vs full, are the pros/cons listed accurate, or are there other issues to worry about?

They seem accurate, so you have done some research. Have you stepped the trenches as well to save on the digging?