Hi,

I had a professional tiler tile walls an floor in my bathroom. However, the floor tiles have started to make sqeaking noises and the grout has cracked and popped out from between the tiles. This happened literally after 48 hours.

Looking at it i can actually see the floor moving when i tread on it.

My view on this is that i hired a professional tiler because i don't (until now) know anything about substrate preperation, floor flexing etc etc. The tiler used flexible floor tile adhesive and cement based grout with a flexible additive.

Long story short - i have taken all the floor tiles up again (which was surprisingly easy as they came up whole). This is the point at which i need advice!!

Looking at the floor it appears to be chipboard. It was laid in 1991 and must have gotten wet during the preceeding 20 years as it smells damp in areas and crumbles to if you touch it. It's basically useless. Where i dug a hole through it there is plastic underneath which i am assuming is somekind of drylining/damp course.

I can't seem to find "joists" as it were. The thing seems to be floating on timber batons and is quite odd i would say!!

Having had quite enough of all this i have hired a carpenter and asked him to look at it. My question is therefore what should i be getting put down so i have a rock solid platform for floor tiles??

Currently i have asked for 25mm WBP plywood as effectively floor boards? Is this right?? Is this going to be good enough for tiles?

Any assistance appreciated as my wallet is struggling to cope with this "quick" refurb!!

Either way i'd get the chipboard up to confirm what type of floor it is. it could be a floating or a suspended floor, if the later get your chippy to add extra noggins and then lay the 25mm ply. I can't comment if floating floor as not enough experience in subject, but i'm sure there are others who will have on this forum. Try to put some photo's on so that we can see your problem.

you have a floating floor

it might be constructed with a concrete base, then insulation, then vapor barrier, then chipboard

I'm assuming that you didn't have tiles down before but maybe a lino?

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This is what was happening with the tiles.

The picture with the bare floor is me having just taken it all up again.

There were tiles down before, but some of them were cracked, the grout was filthy and the whole thing needed a re-do. They were laid on the same chipboard before, but with 6mm ply. The floor is definitely of the floating variety. I don't know if it has concrete underneath as i didn't want to break the insulation...calling an expert before i get out of my depth too far.

I just want to be sure that 25mm WBP ply is gonna cut the mustard and that i am not going to end up with more problems down the line. I need to weigh up whether to just get some Amtico flooring of something laminate and forget the tiles all together!!

if you take the ply up you can see how strong the joists are and strenghthen if required and add extra noggins. the 25mm ply will be solid enough if the joists are soild but i'd put 6mm backerboards down too as they're a better substrate to tile onto.

overbaord with hardi for extra strength as mike suggests, but make sure that there is sufficient stability and no movement with the ply.

It does seem like a floating floor..

You need to remove all the damaged boards .. you should find insulation underneath and this will be laid on DPM membrane..

You have the option to batton the floor and affix the 22mm ply to this or you can use fast settng screed and screed the floor back up to height.. either way it is not a suitable floor to tile to as it is..

And to a reply above.. Hardibacker is not to add strength to a floor.. the floor should be solid to start with.. hardi just gives a better moisture stable floor..

Is the backer board a must??

The chipboard i presume is 18mm which is being replaced with 25mm ply. If i add hardibacker at 6mm (or more) plus the adhesive and tiles it's gonna be a bigger step than i would like!!

The carpenter was talking about adding metal straps across the boards too?? Something to do with holding it all together more firmly. Is this normal??

hmmm not sure, depends on what he intends to do with the straps, holding it together isn't the problem it's the deflection (bounce) that needs sorting out