Bathroom floors have rotted......how to replace

[badhairday]

So, it appears there has been a leak from my shower tray into the floor of my bathroom and now I have peeled the lino back to discover that the floor is soaked through and through.
Once I have got a plumber to find the source of the leak, I will have to replace the floor.

The bathroom is on the ground floor and the current floor is concrete with wooden joists holding up a chipboard floor, which iin turn is covered in lino. My question is, how do I attach joists to the concrete floor? Is there a way around using joists eg can I just put down insulation or something. I have to raise the floor of the bathroom so that it is level with the rest of the house. so just carpeting the concrete floor is out of the question.

Also, only a square foot of the floor is damaged. Should I remove the whole floor or can I remove just a part of it?

Complete novice here.

 

[Symptoms]

bhd - classic problem with chipboard flooring in bathrooms. How do you know the timber joists have been affected by the leaking shower? If you're lucky, and my guess is that you will be, only the chipboard will have to be replaced; joists really have to have been wet for some time to have rotted all the way through or for their structural integrity to be compromised.

Don't bother replacing the whole floor (unless you really want to - use 18mm exterior grade ply) - just cut out the affected bit of chipboard (the stuff like tobacco) back to solid and mid-point over joists. Screw replacement patch of chipboard in (where you might have butted edges support below with glued & screwed batten).

How to cut out the patch? Couple of methods:
circular saw, set to depth of chipboard (as a novice you might not have the confidence to do this, but what better way to learn)
or
jig saw
or
flooring saw (manual method - curved section for cutting - get a cheap version of this saw in a DIY shed)

Before cutting through any floor check-out pipe/cable runs.

 

[badhairday]

Just wanted to say 'thanks' for the response. You were right, the joists are fine. Will replace affected area with chipboard.

 

[JohnD]

the floor will need to be ventilated with a couple of airbricks (on different walls) for the joists to dry out.

I slosh any timber that has been/might get damp with Cuprinol Green as a defence against later rot.