I have a house in Japan that has a plywood (?) board floor in the kitchen. The floor is a bit "spongy" in that in places it dips between the joists. This started about 6 months ago and seems to have stabilised. Underneath the floor is a gap about 40cm or so and then the concrete base. It's supported on joists. Guess what – no insulation.
My first thought was damp of some kind. I've checked and I can't see any leaks. There's excellent airflow through the air bricks.
The sponginess appears to be tied to an area about 1.5 metres on a side by the changing room door and the underfloor storage compartment.
The house was built circa 1994 and reformed 6 years ago – although I have no idea what was done.
My plan is at some point to remodel the kitchen, including replacing the floor (probably with proper floorboards rather than sheets of wood). Coming from the UK all of my previous houses had floorboards so this is a new experience!
Any thoughts on what might be causing this and how to stop it affecting a future floor?
by ross-hori