Working in a Victorian house today, lady wanted me to look at her bathroom floor which she said was 'bouncy'. Not been right since some alterations to the central heating a few months ago.
The floor (4' x 6') was indeed bouncy. Removed the vinyl expecting to find soggy chipboard, but no. Suspected over notched joists.
Turned out to be floored in 12mm chipboard!
The mind boggles................