I have a commercial building which will have retail outlets I know it is 2 layers of 5/8 drywall for the ceiling what is it for the walls do I have to use 5/8 or can I go with 1/2 for the walls
If the entire facility has fire sprinklers, then it doesn't matter, unless there is a "sound rating" requirement. Otherwise:
For 1-hour WALLS use 5/8" Type X (fire code) gypsum board on each side.
For 1-hour CEILINGS use 5/8" Type X (fire code) gypsum board on bottom of joists spaced up to 16" oc with fire rated assembly on top. (If it's an attic, you'll need fire rated roofing on fire rated assembly.)
For 2-hour WALLS use 2 layers 5/8" Type X (fire code) gypsum board on each side. Stagger the joints in the gypsum board both ways (horizontal and vertical) and use approved nailing pattern (length and spacing). Also, there are requirements about extending it beyond the edge of the building too.
For 2-hour floor-ceiling assembly they are not available for wood construction (cut timber) only for steel trusses, concrete joists, etc. and fairly difficult.
Exterior walls are not required to be fire rated, only "party walls" unless you are within the setback area from the adjacent property line.
As you can see, this is very complicated and you'll probably need some professional help from a local architect. By the way, you can't do the work, unless you are a licensed contractor in your state, even though you own the building. Bummer.