IBA: Buildings and Structures: Meaning of structure
There is no definition of building in the IBA legislation. In this part of the manual building means building or structure.
You should treat something as a structure if it has been artificially erected or constructed and is distinct from the earth surrounding it.
Land that retains its character as land is not a structure, even if it has been cultivated or modified in some way. For example, grass tennis courts, grass football pitches, grass bowling greens and golf courses are not structures.
There are no tax cases about the meaning of structure but there are several rating cases. In one of them, I*nland Revenue Commissioners v Smyth 3KB406, *the point at issue waswhether a road was a structure. In that case Scrutton J said that:
In my view it is a question of fact in each case; a gravel path though from repeated gravellings it is harder than the surrounding soil would not in my opinion be a structure, while the roads one is familiar with in Switzerland, the Tyrol, and Italy, in parts built up on mountain sides, in parts cut out of solid rock, would I think clearly be structures, as would the elaborate compositions of concrete, wood blocks, and tarmac used for heavy motor traffic at the present day. Between the two there is every variety of degree of solidity and permanence. Again, the modern earth banks of a reservoir, recently erected and continually repaired, may well be a structure, while the huge earthworks, long ago constructed and repaired, but now become part of the original earth and left to weather with it such as Maiden’s Castle, Flower’s Barrow and Badbury Rings in the county of Dorset, or Grim’s Dyke, Offa’s Dyke and Dane’s Dyke, as they run through England, have, in my view, long ceased to be structures, and become natural features of the earth. I think a structure is something artificially erected, constructed, put together, of a certain degree of size and permanence, which is still maintained as an artificial erection, or which, though not so maintained, has not become indistinguishable in bounds from the natural earth surrounding. What degree of size and permanence will do is a question of fact in every case.