Joist direction and T&G chipboard removal advice

[john2k]

I’m stripping out my bathroom currently. I believe that it currently has a form of tongue and groove chipboard with some sort of grey top layer so not sure what sort of floorboards it is. I’ve attached a closeup photo of the surface.

Three questions:

1. All the floor boards have uniform join lines with screws. Are the joists likely to be going in the same direction as the joints or the opposite? So if joints a vertical in the floor boards, are the joists likely to be horizontal?

2. Since this is tongue and groove, what’s the best way to remove? I’m assuming I need to find the end and start from one end?

3. What is the grey top layer on the board? Has it been tanked maybe?

 

[23vc]

that looks like cement/backer boards, which would normally be tile adhesive’d and screwed down onto ply/timber/chipboard. If so, the screws don’t indicate joist positions as they only go into the subfloor not the joists.

 

[simplesteve]

Yip, these are tile backer boards, and as 23vc says, will be stuck down with tile adhesive and screwed. They don't come tongue and grooved - will be straight edged. The substrate under that is ' likely' to be: for older houses tongue and grooved floorboards which will be at 90 deg to the joists, and for modern houses will be sheets of t & g chipboard.
Unfortunately, if you really have to take them up, it's gonna be slow and tough.