The build is finishing up as I type. I received mixed opinions on split level, mostly the feeling is, that they sound great but practically they are a pain in the a.....Of course this is specific to our build. Yours may suit a sunken living area. We ended up splitting the area between the two bedrooms/bathroom and the lower level living room. We just have a small 3 rise set of stairs, 900 wide on one side. So it retains that living room and the adjoining deck on the same level which was important to me. Visually it means we don't have one large room split in two. The stairs are internal, and just at the side. I hope that makes sense. Every space is different is another thing I learned during this process. Prioritize the important things for you (ours was this adjoining space on the one level so the kids could run around and not fall down stairs), and do your plan according to those.

Your levels are tricky. That crushed granite must drive you crazy being tracked through the house....nice for a side pathway or driveway though. For decking or concrete you will need to excavate. Hmmm, probably same for paving, although not as much. I'd pave it....a nice thin, large profile stone paver.

Without knowing your location and local building regs split-level is a great concept but needs more clever design thinking at the early stages to get it right. The height and floor levels are crucial in the design concept but some architects/building designers struggle with resolving this third dimension well. Apart from your budget, and the amount of excavation required the relationship between the height of the building and setback from your side boundary will be the crucial element which will influence the design response. Leave it to the professionals ... Best of luck, Dr Retro of Dr Retro House Calls

some dimensions are inconsistent ..please check measurements for all rooms including bathroom, laundry, toilet, cellar and retreat and what is the height of the space under the stairs?.. without at least 2m headroom the cellar can only be used for storage unless you are prepared to rearrange plumbing and do you mean that you want the kitchen and casual dining to be reversed but what about the old kitchen window and what are the walls and floors built out of?