Hairline cracks in tiles - where plywood joins

[SkipFeeney]

Hi,

I had a tiled floor laid in my kitchen last year in April. Its started to crack in a line and I removed the kitchen plinth and realised its where the join is between 2 plywood sheets.

I used 18mm marine ply screwed into the joists and floorboards..but looking back at some photos I have realised that I laid it in the wrong direction I laid it parallel to the joists!

Is there anything I can do? Does the whole floor have to come up again? The plywood runs under the kitchen as well, it was fitted before the kitchen fitter came.

Thanks

 

[vinn]

The plywood sheet should have been screwed into the floor boards not the joists.
And, as you say, it should have been fixed across the boards. But if you have T&G floor boards then they should be pretty steady.
Does the join come over a joist or floating in the joist bay(s) between joists?
Were the joists firmly fixed with no flex or bounce in the floor before the ply was laid?

If you have joist flex or its the ply thats flexing then you have a tough call to make.
In the event of lifting the floor its possible to do it while leaving the base units in place.
Can you get to crawl below the suspended floor?

 

[foxhole]

Are the tiles cracking or just grout lines?
Did you use flexi adhesive and grout?