Elevated Slab Question

[JohnDesign]

I am working with a residential design in a high wind zone area of North Carolina. A common foundation type is an elevated slab. A common building method was to build a foundation wall made of brick on the outside with either a 4” or 8” inch block bonded on the inside. The brick is an integral part of the foundation wall, mortared and tied to the block (not a veneer). At the top of the wall the block is stopped and two additional courses of brick are laid. The slab is then ledgered on top of the top of the block wall up against the two courses of brick (with an expansion joint). The bricks then fully support a 2x4 wall. The building inspector has said that an engineered solution is not acceptable and that the top of the wall must be at least 6” IAW the code. The 4” brick fully support the loads of the structure and the design incorporates all of the high wind zone uplift requirements.

Several different alternative options have been discussed but they seem to have other undesirable outcomes. One was to bring the block up flush with the brick but then to have a floating slab but up against the block. This results in the block being the first 4” or 8” of the floor (next to the exterior walls). If the slab ever settles (because it is floating) then you end up with an uneven floor.

Does anyone have any suggestions for any other design approaches?

Thanks

(Below is a representation of the design)

(Slab)
00000000000000** (Brick)
00000000000000** (Brick)
****** (Block and Brick)
******
******
******
****************** (Footing)
******************
******************

 

[apsix]

Two possible methods;
- Take the slab edge to the outside face of the brick, and extend the cladding down to cover the concrete.
- Use 8" block to underside of slab and 4" block between the slab and brick. Not a nice detail to try and achieve a flat floor, and the soft joint will have to be abandoned. To stop relative movement, reinforcement ties between slab and wall could be considered.
The Building Inspector's approach does seem narrow minded, especially if it is a tried and tested detail.