What is the steepest possible gradient of land on which houses can be built?

Basically I am trying to do some research for which I need to know the % of land on which buidings cannot be built in a state. I need an approximate idea of the slope that would be too steep for building structures on. So when I look at a digital map I can calculate the area of the land that is so steeply sloped that houses cannot be constructed on it. Are there any building technology or construction experts out there who can help? ThanksWhat is the steepest possible gradient of land on which houses can be built?
That depends on how much you're willing to spend to build the house. If you drive steel supports deeply in to a rock cliff face you could build on the side of a completely vertical or even overhanging cliff!





I think that for your purposes, however, you could arbitrarily pick about 45 degrees and do well-enough. However, the structure of the soil has more to do with the problem than the slope of the land.What is the steepest possible gradient of land on which houses can be built?
45 degrees below zero
The anasazi indians built housing right into the side of 90 degree straight up rock faces. So I'd say any grade is possible.
Here in the West Virginia Alleghenies, there are houses next to the hill on one side, while the other side is propped up with poles. My house is on a local maximum though, on a ridge surrounded by a dip with even higher elevations further on. My house is nearly level. But the distance from the ground to the roof is greater on one side than on the other.