franks
dymonite69 is correct. Builders are not 'geared up' to do different types of construction methods.
For example, zincalume cladding would be better done by roofing plumbers, who naturally have all the specialised tools necessary, and have experience in the fitting of corrugated steel sheeting, and know what works and how to do it.
My brother is a plumber, and I've worked with him on a roof or two, and there is definitely specialist knowledge and specialised tools that make the job run smoothly. Ever tried using a pair of tinsnips to cut a curve in a sheet of corrugated steel?
You need a special set of snips. Also, did you know there are right-handed and left-handed snips? For cutting in such a way as to leave the waste material on one side or the other, not necessarily for left- or right-handed users!
jenleh
The design principle you are talking about is commonly called Earthwalled construction, or Earth Ship design. Google the terms and see what you find.
Earth Garden magazine has featured at least one Earthship (can't remember the issue no. but if you called them or emailed them they have a list of all stories and could provide a copy of the article for you - at small cost, of course).
Kevin McCloud also featured a pommy Earthship built in northern France in one of the Grand Designs episodes. They are out on DVD I believe, so that might be good for inspiration as well. Although I wouldn't recommend the "rammed earth in old tyres" method they used, but the house itself was fascinating and the way they used free labour to build it was clever as well.
Seems to me that what you are looking to do with your hillside site is what's known in the trade as "cut and fill", where you excavate back into the hillside and use the excavated material to "fill" the slope in front, thus requiring less excavation and enabling slab on ground.
Depending on the site, it might pay you to do a double cut, the upper one for the house, and the lower one for "underground" concrete water tanks. Construct/install these first and then back fill over the top, then lay the house slab over that. Much better utilisation of site space if that is limited.
OP who suggested concrete-block wall tied to the slab is correct. This is the best way to create the retaining wall which is also the back wall of the house. Waterproofing is THE major issue! From my reading about many such designs, multiple membranes provides a better solution that attempting to rely on a single membrane.
The membrane which goes under the slab MUST return up the retaining wall to ground level (and higher preferably) then this should have an additional, more robust, seal or membrane added to it prior to the backfilling of the cut. Again, as OP said, it must have large ag. drain pipe at the bottom, geofabric over this, sand above that and then aggregate over that to help drain any water which filters down to the wall.
Other issues to be aware of is that it is difficult to comply with light and ventilation statutory requirements for any rooms located against the back wall/retaining wall.
You may need to think about roof skylights, which tend to let in heat as well as light, and rather detract from the whole "earthship" idea. Small "light wells" can work, but again, drainage can be an issue. The home in Earth Garden (which I think was in western Vic or S-E S.A.) had a light well.
This is a hollow space, like a miniature courtyard, up against the back wall, so that rooms adjacent to the light well can have windows opening onto it. Can be a design feature as well, utilising plants to shade the 'courtyard' but the trick is to keep it small so that too much heat cannot enter. Also helps with ventilation providing a 'vent' at the back of the house, if wind direction is from the front.
Then the main front wall can be, say, rendered strawbale separated by large double-glazed windows.
You could even go the whole hog and build additional strength into the roof and then cover the roof with a membrane, geofabric and topsoil and plant a roof garden. There was one of these recently in Earth Garden that had a corrugated zincalume base, and was curved for strength.
But the key for you will be the designer. You must find one who has previously built the type of house you want, so they A) know what the design and regulatory problems will be (and can argue with Council inspectors and planning department) and B) has some affinity with what you are trying to achieve.
Designers always ask "what's your budget". If you have a finite budget, tell them it is actually 25% less than it is to allow for unforeseen contingencies. Most "bespoke" builds go over budget by not less than 10%, but can go as high as 50%.
Be sure to include all the enviro systems you want as part of the "total build" price, then subtracting those costs (eg: solar PV, solar HW, underground tanks) will give you an ACTUAL budget for the house construction. Deduct 25% from THIS figure, and that's waht you tell the designer is "the budget". Trust me, it will go over budget and you do NOT want to be compromising passive solar or active solar features because you've run out of money paying for the excavation or the specialist waterproofing supplier.
Strawbale is something you can do yourself, so you get a bit of actual involvement in the building process, too. Sanding and painting is another area that you can save a few grand by doing it yourself. Sure, it takes longer, but if it means you stay under budget and can afford everything you want, then why not?
Project management, as many of the couples in the Grand Designs series did, is another great way to build something a bit more complex (and thus more costly) and save money doing it. Many of them, women included, had NO previous experience building or project managing, but still managed to make it work for them.
It is unfortunate, I believe, in our times, that people have so little actual involvement in the building of their home. The "industry" has thoroughly stitched us up so that we can only buy "packages" - a home as a "product" - just like buying a TV or new fridge.
"Display home villages" are just the "supermarkets" of the building industry, and as others have said, they only want to sell you what they have "on the shelf".
If you want a "biscuit" that looks and tastes exactly like all other "biscuits", buy from a supermarket. But if you want a proper home-made cookie, then find a recipe and a chef who knows their stuff, and get baking!!
Good luck!
