I once built some low platforms on a mesa, and we constructed them with 45*220 because that was the height the customer wanted. As I see it, you can either build with 45*70 in two steps or take 45*145 in one step, depending a bit on how it looks, since it really must not be too high in a hair salon because it can cause big problems for older people to get up. But I would probably have set it at cc 60 and braced between in some places, so you achieve quite a lot of lateral force, but if you are going to lay tiles, you should first have floor chipboard and then a dead material like floor gypsum since the chipboard is a live material, tiles can come loose, and it's easier to get the adhesive to stick well on gypsum. Regards, Jonas P.S. Please feel free to contact me if you would like help with drawings or any other questions.
