Oklouise, do you mean like doing a self contained granny flat but attaching it to the back of the house and using a deck (indoor/outdoor living) extension on the original house as the roof/ceiling to the granny flat? That is a good idea that I hadn't considered. I think I would have to make the ground higher because I believe the rules have changed regarding minimum habitable ground level since the original house was built. The inside walls of the house are 2.7 metres and so there may be some scope to step up to the deck addition (not sure how this would look though...not ideal). It could end up getting quite expensive doing the extra downstairs room as appealing as it sounds. Most additions that I have seen on Houzz appear to work out at about $3000 per sqm (a lot more than the $1500 per sqm that is often reported generally). I keep thinking of having the planned ensuite just a walk in robe in order to avoid having a deck backing onto a bathroom (and to keep costs down), but I doubt I would save much by not doing the second bathroom given that the plumbing for the second bathroom is largely just an extension of what is happening for the "main" bathroom.

Hi Kristin, Unfortunately there's not a simple answer for this one way or the other. Generally 2 storey will cost more, but the cost of a simple two storey design compared to a complex/high quality single storey of similar floor area could be less. It really depends upon the design and level of finish/detail. Cost/m2 rationalising really only works for volume industry where there is relatively quantifiable correlation in this regard. As soon as you get into custom territory things change and can vary dramatically. Good luck! PD www.pauldistefanodesign.com

Hi Mic, Seek out a draftsman or designer who has focus on sustainability and can conduct an Energy rating as part of the design process. A designer who has their Cert Iv in NatHERS is qualified to assess and design for these issues. On a rough calculation - standard WA construction, 25° roof, 500 wide eaves, ceiling at 2.435h then a setback of 1.700 should allow for the sun to strike the floor at equinox, if you have full height windows. Best case scenario place the house between 1.7 to 4m from the fence/retaining. The further it is the more sun strikes the slab during winter. You question about increasing the ceiling height - yes that is a good work around, going to to 3m high may cost more than your think. Another 3c/300mm in height will give you more sun penetration in the winter if your windows are raised and would be a more cost effective solution. But there are many variables such as planning, engineering, buildability and cost. Speak to an qualified designer or architect and they will have the knowledge and experience to deal with all the conflicting factors.

We too live in a cold winter climate with our bathrooms all on the southern side and faced similar issues as you do. One smaller bathroom does not have a window so we put in a Velux skylight which provides amazing natural light through the day. This may not be to your liking, especially if you have a period home. We also use heated towel rails and under tile heating (just enough to take the chill off and stop mould) in winter. Although we have a light in the shower recess, a bonus is the large fixed shower head with inbuilt LED, which at night gives the feeling of showering under moonlight. We chose light colours and mirrored recessed cabinets to reflect as much natural light as possible.