"GB" wrote in message news
On 26/12/2016 14:04, Moron Watch wrote:

Any fool can tell if a floor is sloping by dropping a ball on it or spilling a
liquid, just as they could by using a spirit level.

The question being posed all those years ago is how much it
would have to slope for you to notice it without the aid of tools
or apparatus of any kind;either deliberately or by accident.

I genuinely think that 2cm in 4m would be noticeable. Maybe not just walking along it,
but when you put a run of kitchen units or a wardrobe on it.


But that assumes surely that the walls are still truly perpendicular ?
If a building with a rigid steel frame were struck by an earthquake
such that one end dropped by say 20cm then its quite possible
that all the interior angles of the frame, and thus the corners
of the rooms remained at 90%. So just as you have might have an
imperceptibly sloping floor, so you might also have imperceptibly
sloping walls which can accommodate kitchen units or wardrobes
without giving any visual clues at all.
Although obviously if you decided to store balls or loose
liquids on the shelves inside the units or wardrobe then that
should possibly give the game away.