Replacing rotten solid wood bathroom floor

[Jon c]

Hi

I’m replacing my floor in my downstairs toilet as the existing solid wood flooring was bowed and ruined due to a water leak some time ago. I’ve pulled up the existing solid wood boards and the chip board subfloor underneath is covered in mould, although it is dry now. My plan is to cut out the chipboard with a circular saw and replace it, and then I will lay these solid wood boards:
https://www.directwoodflooring.co.uk/elegant-natural-oak-brushed-oiled-solid-wood-flooring.html

I have a few questions about how to lay them though:
1) what sort of underlay should I use once I replace the rotten chipboard?
I was thinking plywood but not sure.

2) how should I attach the solid wood floor boards to the floor?
Existing ones were nailed straight to the chipboard, but I don’t have access to the machine required for this. I was thinking of using an adhesive, as I have heard solid wood flooring us to be attached to the floor and cannot be left as a floating floor.

How does my plan sound, and how would you do it?
Thanks in advance for any help

 

[Jon c]

These are pictures of the chipboard which is rotten and the existing floor.

 

[23vc]

You sure that’s chipboard underneath? Doesn’t look like it
Subfloor wise ply is better than chipboard, better to replace the whole lot I’d say (if it’s chipboard...)

 

[tomfe]

1: Chip board or ply
2: You can screw along the edges where the beading or skirting will be.

 

[Jon c]

Definitely chipboard, looks like planks of timber due to the solid wood floor that was laid on it.
The new solid wood flooring will run in the opposite direction to the existing one (along the length or the room instead of the width) , so screws at the edges won’t work unfortunately. So would adhesive be the best option?

 

[tomfe]

Since it's not a large area you could just manually pin the boards and use a nail punch to get it below the surface of the tongue.

 

[blup]

Remove and cut the base of the skirting board to accommodate the depth of the new boards.

Blup

 

[Jon c]

I’ve cut out the rotten chipboard, but it was just laid on insulation board, no joists or anything! Surely that can’t be right?

 

[JohnD]

is it laid on concrete?

 

[Jon c]

Yes concrete underneath then the insulation boards on top with a damp proof membrane I think and then the chipboard just floating on it

 

[JohnD]

That can be OK, it's called a "floating floor"

 

[endecotp]

Yes concrete underneath then the insulation boards on top with a damp proof membrane I think and then the chipboard just floating on it

Yes that’s fine, should reaaly have battens around the edges and at the door, but you can probably get away without.