concrete slab (deck) on top of basement wall

[Dannnnnny]

i'm designing a small house (30x40) at hill side, where i have 30' cantilevered retaining wall as a perimeter.
(basement and 2 floors above - so two bottom floors are under soil where temporary shoring is needed)
im considering to have slab on top of basement concrete wall where the rest diaphragm above will be wood.
Is there certain code that specifies minimum thickness of slab?
I have glanced through CBC but I couldn't find one other than specification for slab on grade.
I believed 6" one way slab should work but considering minimum span to depth ratio per ACI, it doesn't look very accurate.
Any rules of thumbs guyS?
Thx

 

[KootK]

i'm designing a small house (30x40) at hill side, where i have 30' cantilevered retaining wall as a perimeter.

Do you intend for this wall to still be cantilevered after the slab is cast atop it? Normally this would turn the wall into a basement wall spanning from the foundation to the slab diaphragm.

I believed 6" one way slab should work but considering minimum span to depth ratio per ACI, it doesn't look very accurate.

Those ratios are for transverse loads. How far will your slab be spanning between lines of support? With this be a CIP flat slab or slab cast on metal deck?

 

[r13]

Table below is ACI recommendation for 2 way slab. Note in no case the slab thickness shall be less than 5" for flat slab w/o drop panel, and less than 4" for flat slab with drop pane. I think CBC shall have similar recommendation.

 

[Dannnnnny]

KootK,
some parts still cantilever while some don't due to the presence of opening(stair).
I was considering to span a beam halfway through so that would make it a 15' spanning one way slab

 

[Dannnnnny]

@retired13
thanks for the info. appreciate it

 

[KootK]

some parts still cantilever while some don't due to the presence of opening(stair).

At 30', I suspect that the walls will actually span horizontally across the stairs rather than vertically. As such, they'd really present as concentrated loads in the deck either side of the stair opening.

I was considering to span a beam halfway through so that would make it a 15' spanning one way slab

At a span to depth ratio of 30 (6" slab), that's starting to get up there for a uniformly loaded slab. This will actually be a transfer slab for the wood structure above, will it not?

 

[r13]

Thickness of one way flexural members.

 

[jayrod12]

I really don't feel that you're going to get the best advice on here if you don't provide a little more information. Show a floor plan indicating intended lines of bearing, openings in the walls/diaphragms, etc. Then you'll get some people chiming in.

A 6" slab spanning 30 feet? Definitely not. A 6" slab spanning 15 feet? Still questionable. How large is the floor openings? Where are they in relation to the walls?

A more complete question would get you a more complete answer.

 

[HauerEng]

A 30' high retaining wall supported by a 1,200 sq. ft. 3 story house which I assume is wood framed, (you site the California Building Code- CBC)?? You won't get the wood framed house to carry the EFP of the retaining wall, especially considering seismic forces which should be given to you in the soils/geology report. Also, not sure if the CBC/AISC allows you support earth pressures with wood diaphrams and wood shear walls- so entire structure should be concrete or CMU, (for the walls). I would suggest having the retaining wall separated from the house and probably support the retaining condition with soldier piles or earth anchors.

Good luck!!