Replacing ceramic floor tiles

[colorado]

Hi

I’m removing ceramic floor tiles from my bathroom and looking for advice on preparing the surface.

I didn’t know what was under the old tiles till I started but seems like it’s 12mm OSB on top of original floorboards. The tiles coming off have left a mess of tile cement and some of the wood scratched off. I’ve still got a few tiles to remove and they are proving the most stubborn so I expect the messy board surface to get worse.

My question is what to do now. Should I scrape the cement off to leave a flat surface and if so, how good does it need to be? Or should I just lift the OSB and lay a fresh piece, and is OSB best or plywood or anything else?

 

[Bonni]

I would remove the OSB and lay 12mm plywood, screwed down at 100mm centres.

 

[colorado]

Thanks Bonni, I’ve got the old board up this afternoon. It was nailed rather than screwed so it was a lot of work with a pry bar, but all fine now. Will get on with the new board during the week.

 

[johnny2007]

I would remove the OSB and lay 12mm plywood, screwed down at 100mm centres.

Exactly this + marine plywood.
Treat plywood with Bal prime apd before tiling.

 

[bobasd]

OP,
why not post a photo showing the floorboards and the fixtures eg. WC, ped basin etc that are sitting on the floor boards?
best practice is for all fixtures to be sitting on the tiles but its not essential.
why was the OSB a little water damaged?

your best bet for a new underlayment surface might be 6mm or 12mm backer board instead of ply?

 

[foxhole]

12mm backer board , more stable than ply .