Flooring Problem

[ginlane]

Hi there,
I am in Japan for a few weeks helping my friend in her house.
One of her problems is her hallway floor. It is a kind of fake parquet flooring approximately 1.5 to 2.5cm thick (0.59" to 0.98")
(see attached Photos)
As you can see from the photos there is a hole in the floor 30cm by 25cm or 11.8" by 9.8"
Many Japanese houses are built of wood as is this one, and the house is built on concrete pillars and there is a 55cm or 21.6" hole under the floor down to the ground.
So we either need to fix that hole or re floor the whole hall. (Probably the best option is to re floor the whole hall for as you can see on 1 of the photos, the flooring is in poor condition and looks terrible!)
Also the floor is held up with joists Approximately 40mm by 40mm (1.5") in size and running 25cm (9.8") apart.
Please could you give me any advice on how I might go about doing this. I'm completely new to this sort of thing! Also please could you give different-flooring options / materials. Wood of course, but also other possibilities, I'm struggling to figure out how to fix the hole when there is no floor underneath! (For information: There is no access underneath the house so all the work will have to be done above the hole not below!)
PS. my skill level is beginner but there is no chance of me being able to duck out of this task and getting a flooring specialist in a my friend is broke.
Please use easy to understand terms when replying
Thank you for any help or input you can give me
kind regards Gin

 

[DarisMulkin]

That is OSB. It don't take kindly to moisture. If the rest of it looks like that I'd say replace it all. But find out where the moisture is coming from, top or bottom. Is it 21.6" from the ground to the floor. It could be wicking it up from there.

Daris

 

[ginlane]

Hi Daris,
No that is the only hole but parts of the top layers of the OSB are not looking great in several areas.

 

[Ernesto]

OSB does not look black unless there has been a serious moisture issue - water and or high relative humidity trapped between it and the flooring causing it to degrade and get moldy. Does it smell moldy?

I take it there is a crawl space under the OSB? If so that area needs alot of ventilation and or sealed up with it being connected to the HVAC system to avoid moisture build up in the space.

 

[rugaddict]

doesnt really look like fake parquet----just a lower grade of real parquet---not much more than popsicle sticks held together with wire and glue---around these parts its generally glued down ---thick brown glue with a very large notch---i dont see any glue at all---this floor was popular about 30 to 40 years ago----if its floating it will be a breeze to remove