assuming a spherical rebate in a vacuum

Whilst Amos started creating furnishings for each of the rooms based on the less-than-accurate floor plan which came with the particulars, I went round making a note of all the number of irritating little nook and cranny bits, then went round and measured some of them, then reinstalled Blender on the laptemp, found the file with the external perimeter plan in it then added a bunch of vertices for the interior, to be dragged to orthogonality later.