water damage - what to do?

[versioncity]

Found a smallish patch of water damage in kitchen flat area. Looks like there has been some leak/flooding at some point and not dealt with. The flooring was bending/bowing under-foot so I've taken that up and found it still wet and crumbling underneath. See pics.
Firstly just trying to dry it out by keeping it exposed (and putting cat litter on)

But how to repair? Wait till dry, then some thin ply type wood and then new floor covering back on?

 

[freddiemercurystwin]

Have you stopped the leak?

 

[versioncity]

there is no leak. I think it's been something from the washing machine at some point, which has flooded, gone under the flooring and been left. (it's not my property)

 

[aveatry]

Not going to help now but I never stop flooring like that to just under the units because any leak from a washing machine / appliance can be going on for months and you wouldn't see it but if you go all the way to the wall and seal the perimeter then any leakages will be seen as it make its way out from under the units.
But that is so long as you do not need expansion gaps around in which case any floor that needs expansion doesn't really belong in a kitchen anyway IMO.
As for fixing it quickly and cheaply I would take the whole lot up and think about some LVT flooring https://www.floordepot.co.uk/vinyl-...MIvvLb2oz6iQMVSJZQBh3KqCDKEAAYAyAAEgKFnfD_BwE
And at least have the washing machine out so you can do the floor underneath - furthermore put a beed of silicone left sticking up around the perimeter of that section so that any leeks are contained and will not run off the edge unseen