Do I need to tear it up and start again?

[Halitosis]

I tiled the bathroom floor 5 years ago (upstairs, onto 6mm ply screwed onto the chipboard flooring) but have since had an extension which required an RSJ being fitted just below the bathroom, in which the floor dropped a couple of mm (see dodgy sealant along wall joint). I'm guessing this is the reason the grout started cracking around the first row of tiles, which have developed a little movement.
I was hoping I could get away with re-grouting but the first tile literally just lifted out...

So can I ask you experts what I should do?

1. Carefully lift and replace the first row (grout elsewhere is fine and tiles appear solid)
2. Try to remove all tiles & adhesive and lay new tiles on existing ply
3. Take out the ply too and use thicker ply or something like NoMorePly?

Thanks so much for any advice

 

[JohnD]

do you know if it was a waterproof adhesive?

if not, and you put the tiles in a bucket of water overnight, it will probably soften enough to scrape off.

take up all the ones that are loose enough to remove easily.

It looks to me like you were overly frugal with the adhesive, too.

you will I think need to prime the ply and use a semi-flexible adhesive, but that's beyond my experience.

 

[Halitosis]

Thanks JohnD - so if I'm understanding you correctly, if the adhesive softens in the bucket of water then I don't have waterproof adhesive (honestly cant recall what I used) and have a bigger problem so need to rip the rest up anyway? Or just prime the ply where I've lifted the row and then stick them back down with more adhesive this time.
Cheers for that

 

[JohnD]

waterproof adhesive is needed in wetrooms, and is a good idea round showers, but is often not used everywhere in a bathroom. The grout will slow down water penetration from the odd splash or wet footprint.

I am not an expert tiler so you will probably get more help when someone else looks in.

 

[foxhole]

6mm ply far too thin, replace with hardibacker or similar.

 

[Halitosis]

6mm ply far too thin, replace with hardibacker or similar.

I appreciate and (now) agree with your point, but what do you suggest as my course of action - tear it all up, or try to re-lay the 15% that are loose and/or have crumbling grout?

 

[Halitosis]

do you know if it was a waterproof adhesive?
... put the tiles in a bucket of water overnight, it will probably soften enough to scrape off.

Still hard as nails after an overnight soak, so my tile supplier is seeking more of the same. Thanks anyway for the suggestion