My $0.02 - in NSW designers are NOT registered or accredited, beware. All architects are nationally accredited. I suggest that there are a lot of things you can do yourself before you start - get a proper survey of your block, ensure that you get them to provide angles for anything that isn't square....understand if there are utilities like sewer pipes which will affect your setbacks or useable space...... Go online and workout the sun angles for your longitude and latitude helpful for solar and overall layouts. West facing picture windows are not the best. Some of the solar firms have online calculators which help to do this. Read the local council rules and understand them, apply them to your survey and your design ideas....including if you are a corner block and if you want to go two storey...... If it is still a 'go' Get all of the heritage, flood, fire etc checks done by council - around $150 depending on council........ Eliminate or at least understand all the big constraints before you go any further........ Look again at the survey- any contour lines may cost you money, assume a cost of at least $2000 per sqm to start and do some layouts of your ideas on paper, add up all of the spaces, can you actually put them on your block? How much is the total?.......yes garages are slightly cheaper to build but still take up precious footprint space.... Is access likely to cause issues for trades, equipment and deliveries?......... Keep refining and updating the ideas and plans thinking about how you want to use the spaces and move around inside and out.....where are you putting the wheelie bins, clothes dryer etc..... Try the free to use BASIX site forms if you are in NSW, understand how the size, shading and orientation of windows affects your sustainability and adjust, this will also apply many of the local council rules as well..... Do you want a brick house, with render? A pole home, a kit build? A fast build insulated panel build? What type of roof?...... The more you have worked out for yourself the better, look at the kit home options, there are lots and some are very good... Everything is delivered and you just construct with the trades and some may have builders in your area.....The new InsulLiving Code Mark BCA approved options are also worth a look..... Anyway do all of that before you line up for the fleecing floor lol

Depends on budget. Many dwellings (probably majority actually) don't setdown the floor structure to end up with a flat floor throughout. It costs extra money to achieve for something that is to most people un-noticable. High quality dwellings do this all the time however. If you're going to that level of detail you should also look at setting down the floor edge where the sliding/stacking/bifold doors are (if you have them) so that the door sill is flush. This something you'll see continuously more often than the bathroom/ens floors. It was mentioned on 'The Block' recently and I've now had numerous clients asking about it and/or presuming that this how all floors are done.

thank you for all of your comments. The main issue is that this wall faces quite a steep hill, so if I excavate too much I run the risk of creating a 'pool' under a suspended floor, facing the hill. This would be a disaster for the old double-brick home, which already has damp problems from water from the hill. My other concern about a slab is creating a permanent damp patch next to the house, assuming the black plastic membrane under a slab would be permanently damp (no evaporation). The mortar throughout the original house is lime mortar which is highly permeable and turns to dust when permanently damp John Cameron, I appreciate you mentioning passive solar, I'm familiar with this. Would it be best in this case to put rigid foam (say 50mm) under the actual slab before casting it? There will still be a thermal bridge at the perimeters though. MB Design I like the idea of a graded slope under a suspended timber floor, so will check with a structural engineer as to 150->400 allowance, noting my comment above about not wanting to pond water Two's Company I like the idea of a cement sheet for the wet room area - I have actually done a bathroom like this before and it works with great waterproofing. TBH I'm wondering right now if I should just redesign the whole thing. I'm going to make another post to canvas opinions on the two options and costs. Thank you! Sue

my suggestion has much less demolition including keeping the original outside back wall in favour of a simple skillion roofed extension for kitchen and alfresco, this adds a similar floor area but the shape of the extra space is much more comfortable for dining and family rooms with kitchen servery and extra storage across the full length of the dining area..the new location of stairs keeps everyday traffic out of the living area to create a more private master zone with wiw and ens, group activities in family, dining, kitchen and alfresco plus easy access to laundry, guest bath and bedroom from everywhere and upstairs for generous kids zones..new location for internal access from the garage and more storage in the entry