Derek Sivers on building his house gradually, rather than by planning ahead of time what a house needs:
How do you build a home without predicting? By living in an unfurnished, unfinished place, adding only what you’ve proven you need or want. […] I slept outside, so I know I need a roof, walls, and great insulation. […] I slept on the floor, so I know I need a mattress and blankets.
See also, The Timeless Way of Building.