Extending up and out - question

[Nigello]

I know you can extend 3m from the end of one's property, but does this apply to a second storey too? For example, could an extended kitchen currently under a flat-roofed bathroom, be extended on both floors.

The reason I ask is that my proposed loft extension may be a non-starter because it seems particularly low to start off with and I am thinking of other ways of making space (before the basement option is mooted!)