Slab monolithic with grade beam or raised?

[smillm]

I need your opining. I can use any of the two options shown but which one would be better?
Usually I set the top elevation of the foundation to be 1 ft below the exterior grade but the solution with the monolithic slab seems to much more straightforward.

 

[jhnblgr]

slabs with structural elements are difficult to do. Slabs require a lot of effort in a short period of time to finish properly and also the difficult of working with deep holes around the edge is a safety issue. The second option is a water issue waiting to happen. Slab should not be level with grade and block should really be raised off the floor with a concrete ledge to protect the block from water.

 

[BAretired]

Neither detail is acceptable.

1. Exterior grade should be a minimum of 150mm below the top of grade beam to protect exterior wall finish. (code requirement)
2. Top of slab should be below top of grade beam if slab is to be hosed down periodically.
3. Non structural slab on grade should be free floating, not monolithic with or bearing on grade beam.
4. Structural slab, if used, must be adequately reinforced to span between foundations without relying on soil below. It should be underlain with void form if soil is an expanding clay which is expected to heave with change in moisture content. Usually slabs on grade are not structural.
5. Grade beam should be a minimum of 200 wide x 600 mm deep, but not wider than the wall it supports.
6. Grade beam should be underlain by void form to prevent frost heave unless the underside is below frost depth.

 

[Mark_J]

I'm assuming those are helical piles. It is not uncommon for them to be 4" or so off centerline. I've come to the conclusion you need a portion of the slab to resist the torsion from this eccentricity. Forget about the grade, many times the foundation is basement, well below grade.

I'd thicken the slab and connect it to the grade beam and reinforce the connection and slab accordingly.

 

[jerseyshore]

Never seen a SOG poured monolithic with grade beam. That's just asking for problems. Very difficult to do in practice as well.

I also hate the seeing a SOG sandwiched in between foundation and CMU wall above. SOG's don't typically get poured until further down the line so you mess up construction schedules that way.

We have this condition all the time down here and the CMU bears directly on the grade beam (hidden just below grade) with the vert. reinf. tying them together. Then the SOG's get poured later, usually with a haunch down to the exposed toe of the grade beam.