Can Celotex flooring go mouldy?

[Clareelaine]

We've just had an extension done and the new bathroom floor is tiles with travertine tiles and has Celotex underneath. There has been a leak under the bath and the builder says he doesn't need to replace the Celotex floor and that it will eventually dry out and the water will seep away into the concrete slab. Is this correct or is he trying to pull a fast one? Thanks so much in advance.

 

[foxhole]

No need to replace.

 

[Dextraneous]

Plastic doesn't rot