A site becomes buildable through a small number of mechanisms, and most arguments about development are really arguments about one of them. I write about five here, separately, because they fail in different ways and because a reader usually arrives with one specific problem rather than a general interest.

What I am after here is the portable part. Specific buildings are not portable. The reasoning behind them sometimes is, and separating the two is most of what makes a technical subject worth writing down at all.

The five are structural engineering at extreme proportion, building on and around designated structures, underwriting something with no comparable, the sequence by which a project becomes lawful, and the movement of development rights between parcels. They are not equally hard and they are not equally interesting, and I have tried to say which is which.

Each page sets out a mechanism, what it costs, and a point where a competent peer could take the other side. None of it substitutes for a professional on your own project, and each page names the discipline that should actually be holding the question.