Some thoughts on a planned house?

G'day to all. I've been to the Woodwork forums before and asked questions, and between them and speaking to builders, I got pretty much scared out of building my own home for some time. :D But I'm having another shot anyway.

I'm wanting to built a high-set house. External walls will measure 10m * 12m. After than, I have several options I'm considering:

1) I intend to build/have it built on steel stumps (clearance 2.7m) with the upper story wood construction clad in hardiplank or similar. Single roof peak along the 10m axis. Basically a 'standard' looking house similar to what we've all seen built in the 70's and 80's. I'm not after fancy. Ground floor slab will be preferably Limecrete, to reduce the Carbon emitted during curing (as I understand it, Limecrete actually absorbs CO2). The walls of the ground floor will be either double brick, or metal-sheathed styrofoam coolroom sheets ($100/sheet, apparently). I'm leaning towards the styrofoam.

2) Add a basement. Last time I talked to a builder, he said I was looking at $70K to put one in. That's too much, so I shelved the idea. Recently, however, I came across the Dincell Construction System. It seems ideal for use in basement walls, as not only does it reduce the volume of concrete required, it also reduces the amount of reinforcing steel, virtually eliminates potential corrosion, and is watertight. The problem was the basement roof/ground floor slab, as this was the $$$ part of the basement the builders were talking about. Upon watching a few Grand Designs episodes, I went looking for pre-stressed concrere beams, and found them in Ultrafloor. Again I'd like to use Limecrete if available, but I'm not sure it can reach the necessary strength.
My step-father is in excavation, and after talking to him it seems a reasonable estimate for the earthworks is $10,000 (with some wiggle room). Ultrafloor list a rough 'guesstimate' of $30/sqm, so another $4000 for the roof/floor (plus Ultrafloor items), and Dincell, using their spreadsheet, estimate $16,000 for the basement walls (or $28,000 for the ground floor walls as well). The only thing that concerns me is the potential for seepage at the wall/slab joint.

I always told myself that if I could get a basement for $20,000, I'd do it, but the immediate family is trying to talk me out of it.

The site is located at the base of a small hill (it's maybe 20m from the lowest part of my plot to the highest part of the hill, and that's over 300m away). There is a fall in the block of about a metre from the highest end of the proposed house site to the lowest, along the 10m axis.
Last week, I hired a Soil tester to drill two test holes to find out where the ground water was, due to the blocks proximity to a creek (eyeballing it, the creeks' regular level seems to be about 3m below the house site's lowest point). At the high end of the 'house', he went down 3.2m and hit sandstone, with no water layer at all. At the low end, he only got down 1.8m before hitting sandstone, again with no water. I expect that if some of the sandstone needs to be removed, that'll be a right mongrel to do.

WRT the finish of the house, I'm intending to simpy have it built, professionally, to lockup, with only the bathroom and kitchen (ie, the wet areas) finished, then finish the rest myself (have to do an Owner-Builder course before any of this happens), with some help from friends and family (The Other Half has already called dibs on the painting. She enjoys it for some reason :cool: ).

So this is sort of an open thread. Does anyone have any suggestions, advice or questions? Cheers.


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