What is Planning?

Planning is distinct from Design and it should come first. Here is a parallel with buying clothes that helps explain the differences between Planning and Design. 

The clothes-buying process begins with the recognition that you need clothes. Planning steps would be A) determining what kind of clothes you need (coat, dress, slacks, shirt, shoes); B) the context in which you need the clothes (beach vacation, formal dinner, work); C) the constraints on the clothes you might select (conservative/flashy, the season, your size); D) the money you have for clothes or how much you can afford to spend; and E) when you need the clothes (special event, or some other basis).

The Design steps would consist of shopping (visiting stores, selecting and trying on clothes), and then buying the clothes and wearing them.

If you start with shopping, which is like starting with Design instead of Planning, it is easy to see that you may overlook something fundamental when you find clothes that you really like the looks of. With a building project it is inevitable that you will overlook something because it is so much more complicated. The result is wasted time, effort and money.