I subcontract, and went to a job the other day. The ladies bathroom floor had 15mm ply laid on it, but the plumber cut a large square out (maybe 1m x 1m) and refixed it with a few screws. The second I walked in the room, I could hear movement. I told the lady about it, and she was very worried. Was talking about putting lino down instead or something like that.
I was happy with that as we were not being paid for any preparation work, and I was instructed to not do any as it should have been done prior to us arriving. This tells me the guy running the job is doing it as cheap as possible.
So anyway, I start tiling the walls, and the lady comes upstairs with the contractor, and he says to me "Im on holiday on sunday for 3 weeks, if the floor isnt tiled, they wont have a toilet for 3 weeks." so I told him what needed doing to stiffen the floor substrate, and he cut me short like I was boring him, and told me "am I not using the special orange matting?" to which I replied that I would be, but its not magic and this floor in its current state would reject its tiles in under a few days. He then came at me like he was spelling things out really simple and basically told me to "get it done", to which I asked him to sign this cover note with the home owner detailing my concerns and leaving me not liable to any comebacks. Neither would sign, I walked.
Nobody ever signs.