We have a piece of land with about a 9ft difference in height between the proposed left and right corners of our future house. What are your suggestions on the best way to minimize cost on building a (slab) foundation?
Obviously, you can’t build a slab on a slope, and that is quite a slope. If you have enough land area you can have your excavator scrape a level spot for your house, but that will create a “low” point in the land and a horrendous potential for water problems. Water is a builder’s worst enemy. What you should do is plan on either a raised slab, or a walkout basement.
In your case, a raised slab will be 9 feet higher on one side and building that will be rather expensive as it will require a foundation wall to hold the "compacted" fill dirt/sand. You could make it a little lower by "leveling" the land a bit, but each foot you level, increases water problems.
A walkout basement may be an alternative. By building a walkout basement you will be digging into the "hill", pouring a slab, and building a foundation wall on the sides that remain below grade while wood framing the rest of the walls. A picture of a typical walkout can be found on byoh.com at: http://byoh.com/basementwalkout.htm. Water is easily control ed on this type of foundation. It will cost you more than you were planning, but you are potentially increasing the living area of your house. You don’t have to finish that area off, but it’s there for the future.
Get together with a good foundation contractor and a professional land surveyor on your job site and discuss your options.