Gap appearing between floor and wall tiles of new bathroom

[J_3926]

Hello,

Our bathroom was installed 9 months ago by what we know were tradespeople who did not have the skill or experience to do so. Several revisits to fix leaks, poor siliconing and retile whole wall and reinstall shower tray were needed and in the end we just accepted it, even though it’s clearly a bad job (and still wasn’t completely leak free).

9 months on and a gap is appearing between the floor and wall tiles. It’s only on one side of the bathroom, which is the external wall of the house. It an old Victorian terrace. They laid plywood on top of original floorboards then tiled on top of this. We also heard a loud bang in shower one day that suggests something has come loose below the shower tray.

Has anyone seen this before, know what is causing it or what they have (I assume) done incorrectly in laying the floor/tiles?

Thank you in advance for any advice.

 

[Timmy D]

Pics? Perhaps the old bathroom had a lon slow leak and has rotted the joist.

 

[J_3926]

Hi, thanks for the reply. We had the ceiling below re plastered and joists visible and the very experienced builders who did that said the joists were fine. Clearly there must be movement and it’s a old property but shouldn’t a professional bathroom fitter prepare the floor accordingly?

 

[Chuck]

A photo showing the gap would be helpful. How wide is the gap and is it changing?

A relatively common problem with Victorian terraces is owners modernise on the cheap by knocking out ground floor chimney breast without replacing the support they provided. Has anything like this been done?

 

[J_3926]

A photo showing the gap would be helpful. How wide is the gap and is it changing?

A relatively common problem with Victorian terraces is owners modernise on the cheap by knocking out ground floor chimney breast without replacing the support they provided. Has anything like this been done?

Not on this side of the house. One of the three chimney breasts has been removed downstairs but on the other side of the house.

Some photos attached.

Gap is around 5mm and growing. First noticed the silicone tearing around Oct/Nov but thought it was just poor silicone. Gap is growing by the week it seems.

I know we’re likely facing ripping the floor up and a probably a total refit. Main things I’m trying to establish are

A) were the tradesmen at fault (their materials and workmanship failed a number of times and I know they only put down 6mm plywood, no other substrate)

B) how can I make sure this doesn’t happen next time around.

If it is the joist then the builders who replastered kitchen and specifically checked the joists while it was open have also failed imo

 

[SimonG]

6mm ply is no good for tiling onto. I would fit 6mm ply if I was putting down lvt or customer wanted cushion floor.

Depending on floor then it would be 6mm hardiebacker or no more ply, glued and screwed. I also like to look under the floor to see if it needs any extra cross bracing.

Needs to come up and be re done correctly.
Preferably by somebody who comes recommended or you've seen previous works.

 

[J_3926]

6mm ply is no good for tiling onto. I would fit 6mm ply if I was putting down lvt or customer wanted cushion floor.

Depending on floor then it would be 6mm hardiebacker or no more ply, glued and screwed. I also like to look under the floor to see if it needs any extra cross bracing.

Needs to come up and be re done correctly.
Preferably by somebody who comes recommended or you've seen previous works.

6mm ply is no good for tiling onto. I would fit 6mm ply if I was putting down lvt or customer wanted cushion floor.

Depending on floor then it would be 6mm hardiebacker or no more ply, glued and screwed. I also like to look under the floor to see if it needs any extra cross bracing.

Needs to come up and be re done correctly.
Preferably by somebody who comes recommended or you've seen previous works.

thanks for the reply. Figured as much but good to have it confirmed.

Fitter that came round yesterday he would also use hardiebacker. Didn’t seem shocked by the 6mm ply so not sure if it’s actually negligence on the original fitters part.

Someone else has also suggested an uncoupling membrane such as Ditra Matt.

 

[SimonG]

Don't need the ditra mat.

 

[Ric2013]

Two layers of ply at right angles was the standard for years. First layer 18mm, 2nd layer used to be 6mm. That said, even if this has been skimped on, it should not result in the floor dropping. More likely is flexing and resultant failure of silicone, not permanent deformation.

Could be seasonal movement of the walls, or due to seaonal humidity: timber reacts to all this. Hopefully not the result of another leak.

A Victorian house: sometimes the build quality is good; in other houses, it is all a bit flimsy and bouncy; in my own Victorian house, I would hesitate to fit a tiled floor at all, as it's a very poor man's cottage and has been chopped about badly an awful lot, and now everything moves all the time. I have come to accept that skirting boards, while somewhat old-fashioned, work well with such a structure; although I am sure more 'technical' solutions are possible; necessary even, if you want a waterproof edge.

 

[J_3926]

Two layers of ply at right angles was the standard for years. First layer 18mm, 2nd layer used to be 6mm. That said, even if this has been skimped on, it should not result in the floor dropping. More likely is flexing and resultant failure of silicone, not permanent deformation.

Could be seasonal movement of the walls, or due to seaonal humidity: timber reacts to all this. Hopefully not the result of another leak.

A Victorian house: sometimes the build quality is good; in other houses, it is all a bit flimsy and bouncy; in my own Victorian house, I would hesitate to fit a tiled floor at all, as it's a very poor man's cottage and has been chopped about badly an awful lot, and now everything moves all the time. I have come to accept that skirting boards, while somewhat old-fashioned, work well with such a structure; although I am sure more 'technical' solutions are possible; necessary even, if you want a waterproof edge.

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?

 

[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!