Tiling on suspended floor

[UncleEbenezer]

I understand it's inadvisable to put flagstone tiles on a suspended floor, no matter how good they look and feel, as they'll be brittle and crack over time with the tiniest movement.

To what extent does that extend also to artificial stone-substitute tiles, such as these porcelain ones?

[servodude]

I understand it's inadvisable to put flagstone tiles on a suspended floor, no matter how good they look and feel, as they'll be brittle and crack over time with the tiniest movement.

To what extent does that extend also to artificial stone-substitute tiles, such as these porcelain ones?

I think you might be able to ameliorate some of the risk with epoxy grout/adhesive; it should be a bit more flexible (and work a bit like an expansion joint)
- but it really depends on how much movement is expected

I believe that porcelain can be made flexible - but it won't be cheap https://www.kale.com.tr/en/kalebodur/kalesinterflex
- how about lino?

-sd

[sg31]

It used to be thought possible to put 1" ply down and tile on top of that. I was asked to do it by a customer many years ago. I refused. It would reduce the flex of floorboards but shrinking of the ply as it dried out or expanded in damp air suggested it might cause issues.

I remember, not long after that, some company brought out a system that was designed for tiling over suspended floors. It's a long time ago but from memory it was a corrugated sheet which was put down then filled with some filler which would set like concrete. It was supposed to stay rigid and the floor could move below it. I never had call to use it and I've not seen it mentioned anywhere so it probably didn't work.

The previous owners of my last house tiled the upstairs bathroom floor in fake marble tiles. They went straight onto the floorboards. It didn't last long. Idiots.

[redsturgeon]

You need this stuff

https://www.schluter.co.uk/ditra-25.aspx

Great stuff

John

[Dod101]

I have what I guess is meant by suspended floors throughout my house. (Boards of some sort on joists with air circulation below) I have three bathrooms all with tiled floors, two with porcelain tiles and the third with some sort of composite material. Two have been down for at least 14 years (just after we moved in here) and I have had no problems. Flagstones of course are going to be much heavier and may not work.

Dod

[UncleEbenezer]

The previous owners of my last house tiled the upstairs bathroom floor in fake marble tiles. They went straight onto the floorboards. It didn't last long. Idiots.

My previous (rented) house - a 1930s 3-bed semi - had the (upstairs) bathroom tiled with real flagstones. Very nice, but I didn't know (and noone told me) they should have been re-sealed every couple of years to keep them in good nick, so I saw the effect of treating them as just a nicer porcelain. No hint of trouble with movement, perhaps because the bathroom - though a decent size - was still quite a small area, and never got put under stress.

The same house had a similar colour/pattern in the kitchen, but that was vinyl or similar and not nearly as nice. Probably more practical in a room with washing machine vibrating vigorously, and of course no maintenance more elaborate than the mop required.

My present house has the shower room porcelain-tiled: looks and feels cheap&basic. Slight hint of unevenness, but seems OK. The room is tiny.

What I'm now contemplating is a much bigger area. It vibrates significantly when the washing machine spins.

Thanks everyone for the thoughts and suggestions. Inconclusive as ever. I wonder if the same issues apply to quarry tiles - not that I was thinking of them for this job?

[Lootman]

It used to be thought possible to put 1" ply down and tile on top of that. I was asked to do it by a customer many years ago. I refused. It would reduce the flex of floorboards but shrinking of the ply as it dried out or expanded in damp air suggested it might cause issues.

Funnily enough I once had a professional contractor around for a job like that, and he told me exactly what you said there. He refused the job for that reason in fact, claiming that he "could smell the damp".

I found another guy, who was more of a handyman than a contractor, who was happy to do the job. And 20 years later it is still in good shape. so what you describe is a risk, but not a certainty. I do use a dehumidifier in there, however, which keeps the humidity constant.

I have what I guess is meant by suspended floors throughout my house. (Boards of some sort on joists with air circulation below) I have three bathrooms all with tiled floors, two with porcelain tiles and the third with some sort of composite material. Two have been down for at least 14 years (just after we moved in here) and I have had no problems. Flagstones of course are going to be much heavier and may not work.

Agreed. I have flagstones on the ground floor, but tiles on the 1st and 2nd floors. There is no way I want all that weight on the upper floors. Plus I can barely lift a flagstone at this point and so they are going nowhere.

[quelquod]

I have what I guess is meant by suspended floors throughout my house. (Boards of some sort on joists with air circulation below) I have three bathrooms all with tiled floors, two with porcelain tiles and the third with some sort of composite material. Two have been down for at least 14 years (just after we moved in here) and I have had no problems. Flagstones of course are going to be much heavier and may not work.

Similar here. My bungalow has chipboard on joists flooring and both bathrooms and the kitchen have been (ceramic/porcelain) tiled for at least 14 years with the chipboard strengthened with sheets of 3/8th plywood screwed at 6” centres. No problems to date. Can’t remember now what glue was used but it was specified as flexible.

My previous house was 3 storey with a bathroom on each floor tiled similarly and no problems. The upper floors had balconies forming the roof/ceiling of parts of the floors below and were flagged on a bitumen underlay on wood. When the house was surveyed there was a comment about the flags and an acknowledgement that the structure was designed to support the loading but there were no issues with the flags cracking or loosening.

[Mike4]

I've tiled many bathroom suspended floors using that really expensive flexible floor tile adhesive made from ground up car tyres, with 9mm marine plywood screwed down all over onto (well fixed) existing floorboards. Only one failure, where I used the recommended primer to go with the adhesive. Others in the trade said they'd had the same, and leaving out the (pretty blue-coloured) primer was essential as it caused the failures. After the failure I tiled dozens of floors with adhesive straight onto the raw plywood with no further problems. This was 20 years ago and some are still customers, tiles still stuck down.

"Balflex", I think the adhesive was called.

[jaizan]

I tiled my bathroom floor about 16 years ago and have had no problems at all. The floor was 18mm chip board. I covered it in PVA and glued & screwed a 6mm layer of plywood on top to stiffen it slightly. I then put some ceramic floor tiles on with flexible adhesive.

I did the en-suite 15 years ago. The chip board here felt more solid, so I didn't bother doing any stiffening work. I used the same flexible adhesive, but belatedly realized it wasn't recommended for use with the granite tiles and was setting very slowly. I put a fan heater in there for a couple of days which solved that problem. I've also had no problems at all with this since completion.

Despite that working just fine, if doing it today, I'd probably rip up the chip board and put plywood in first, as I have gradually got more fussy over the years.