Modular building kit, modular building and method

A kit for constructing a modular building is disclosed. The kit comprises a plurality of wall elements 5 and a plurality of elongate fixing elements 4 for fixing the wall elements 5 to each other or to a fixed structure. The planes of the external faces of the wall elements 5 intersect with a perimeter defined by a regular polygonal portion 2 superimposed on a rectangular portion 1 such that two vertices of the polygonal portion 2 lie on a respective side of a rectangular portion 1. A grid of mutually perpendicular lines 3 is defined such that the lines 3 extend perpendicularly to the sides of the rectangular portion 1 and pass through the vertices of the polygonal portion 2, and adjacent grid lines 3 pass through adjacent vertices of the polygonal portion 2, wherein each wall element 5 lies between two adjacent points of intersection of grid lines 3.