[BBIGG BLOCK 396]

You can also put a layer of tar paper(THE THICK ONE I BELIEVE IT IS RATED 30#) the same width under the bottom plate of the wall,also use ground contact treated 2X4 for the bottom plate of the wall.That will limit any moisture from coming in contact with the 2X4 bottom Plate!Then use the plastic sheating If you wish on the lower part of the wall but I do not think it would be necessary.It would be a good idea to use the green sheetrock in that area due to possible contact of water.I used to frame homes years and years ago and that was a requirement to use the 30# felt or tar paper on FHA homes.We did not use the treated lumber because it was not readily availiable back then but it is now so I would use that. The contractor should use a heavy plastic put over the dirt before he pours the concrete.This is also a moisture barrier and will prevent moisture from coming up through the cement.If you just want to spend the extra $$$ for the concrete curb or stub wall to lay the bottom plate on.I would think it is going to be just like a curb if layed directly on top of your existing slab,it is going to crack and move with much contact.Although if your contractor sets the forms for it during the initial pour you could make it to where it is a part of your regular slab which would be much stronger and they a can also install some 1/2" bolts to hold the bottom plate for the wall down also.