Overboarding Landing Under Carpet, Ply or Alternatives?

[allerton]

I have screwed down the floorboards for a 1 square meter landing that opens to two bedrooms, the bathroom, and the staircase. This has eliminated the creaks, but there are gaps. My plan is to overboard with 6mm plywood, but from reading online I have seen NoMorePly concrete fabric sheets and want to know if this would be a suitable alternative.

I know it’s usually for tile backing and we plan to carpet.

Pros are that it looks easier to install and it’s waterproof. My family have a terrible habit of stepping out of the bathroom soaking wet, so I thought waterproofing this section would be an advantage. I am concerned about water going through the carpet and ruining the plywood.

Cons are that I’m not sure if that strength of the material’s surface is sufficient. Does it only work with tile over it to absorb impacts (e.g., would a high heel leave a permanent dip in the surface)?

I have contacted the manufacturer but wanted to check here too.

 

[allerton]

Wanted to add a photo and ask if overboarding is recommended in the first place? I replaced a few boards. There are gaps to the right of the new boards (especially if you ignore the tongue), and a knot hole in the bottom left.

 

[crazydaze]

Ply or hardboard will be fine under carpet.