Gap appearing between floor and wall tiles of new bathroom

[Timmy D]

I think the British standard for overboarding prior to tiling is 15mm wbp.

I’d always go with 18mm wbp ply and then staggered wedi board over the top. Screw the ply at 200mm centres.

Don’t use shuttering/spruce ply. Get quality hardwood wbp/marine.

If the floor boards are dodgy, or you want the depth, take them up and upsize the ply to inch/25mm. Leave a 3mm gap along edges and joints for expansion. Also seal all edges.

Use a thin bed of tile adhesive on the wedi board to fill any gaps and also screw it down.

Is it only that edge where the gap is? Looks like water has been getting out of the shower seal and on to the floor (as evident by scale, could also be from body when exiting shower). If the silicone went and then water got under the silicone, it could have them soaked in to the 6mm and cause it to deteriorate/rot, potentially causing the gap.

Looks like a redo. If it is tiles on to 6mm ply on floorboards, it’s bad workmanship. Even my dad wouldn’t do that.

 

[Ric2013]

Thanks. But then I’m assuming the floor wouldn’t be flexing quite so much if the correct amount of plywood or hardiebacker had been used, right?

We certainly won’t be putting tiles down again that’s for sure.

Would such movement not cause this type of gap if vinyl or LVT were used then?

What I see in your image is not flex. Flex (elastic deformation) would mean the floor drops when subjected to weight. Whereas the floor just seems to have dropped (plastic deformation). If the joists or wall have moved, the thickness of the ply is irrelevant (unless someone has done something stupid like put the last joist a foot from the wall and left the ply overhanging, in which case the ply itself could sag). Does that make sense?

If vinyl etc. were used you'd still get a gap. What you won't get is tiles cracking or coming loose if the ply is flexing a lot. My point is, going back to example of my own house, most of the rooms have floorboards and skirtings with no seal between the floor and skirting, just, at best, a close fit. In this house, I wouldn't try to seal the gap at all: the house has long trained me to adapt to its general sh-height-ness.

 

[J_3926]

I think the British standard for overboarding prior to tiling is 15mm wbp.

I’d always go with 18mm wbp ply and then staggered wedi board over the top. Screw the ply at 200mm centres.

Don’t use shuttering/spruce ply. Get quality hardwood wbp/marine.

If the floor boards are dodgy, or you want the depth, take them up and upsize the ply to inch/25mm. Leave a 3mm gap along edges and joints for expansion. Also seal all edges.

Use a thin bed of tile adhesive on the wedi board to fill any gaps and also screw it down.

Is it only that edge where the gap is? Looks like water has been getting out of the shower seal and on to the floor (as evident by scale, could also be from body when exiting shower). If the silicone went and then water got under the silicone, it could have them soaked in to the 6mm and cause it to deteriorate/rot, potentially causing the gap.

Looks like a redo. If it is tiles on to 6mm ply on floorboards, it’s bad workmanship. Even my dad wouldn’t do that.

Thank you for the detailed reply. Yes it’s only that edge where the gap is although there is one cracked tile and a grout join that is also starting to crack on the other side of the bathroom too.

I can’t find anything in the BS5385 standards that specifies the depth of substrate although it does say plywood although I’m sure you’re right and that this is poor workmanship.

There hasn’t been much water escaping onto the floor tiles, only recently, but for all I know there has been water leaking through the shower tray/wall tiles silicone join and onto the ply that way, which would be another similar explanation.

I also know they told me they would use a tanking kit and then didn’t!