Tiling onto wooden floors (again)

[frexpt]

I have read the earlier posts on this and very helpful they were.  However, I have found a slightly different set of circumstances now and I wonder whether the advice will differ.........

The plan is to convert one of our upstairs bedrooms into a bathroom and replace the laminate floor with ceramic tiles.  Having taken up the laminate earlier in the week, we find that the floor underneath comprises sheets of something called Placosol, which appears to be a plasterboard product.

The sheets are all stamped "02/2 PLACOSOL 13HD", followed by what looks like a production time and date reference, then "CONFORME A LA NORME NFP 72302C"......the final numerical reference differs from sheet to sheet.

It all looks lovely and level and feels rigid underfoot, but I wonder whether this product needs any special consideration for tiling, or should just be treated as a wooden floor?

[frexpt]

Done a little research and it appears that this is plasterboard flooring product, designed primarily for dry areas........bit of a blow!

Rather than rip the whole lot up, I think it ought to be possible to apply a waterproof sealant to it to get around its porous nature.  Any tiling going on top would have flexible adhesive and grout anyway, so I don't see that much risk.

Question is, will I need anything else between the (sealed) boards and tiles?

[Théière]

If you must use it (risky med to long term) then put down the waterproof membrane used in wet rooms, usually applied in a couple of layers with a resin.

[WJT]

Could you not just put down some waterproof particle board or OSB on top? Schluter makes a good product as well that also helps the tiles from moving in addition to waterproofing, it is the Schluter DITRA.

http://www.schluter-systems.fr/etancheite.aspx

[Nearly Retired (I am now)]

You need a pretty rigid surface to lay ceramic tiles with no chance of cracking. I suspect a layer of plasterboard type stuff will not be enough and I endorse the view of an extra layer (at least) of board.

As for what I do - I've seen too many cracked bathroom floor tiles in too many houses - I always use a top quality vinyl tile like Amtico or Karndean. I'd only fix a rigid ceramic tile to a rigid solid floor.

[PaulT]

Stayed in  hotel last weekend that had wooden floors and the bathroom had very nice ceramic tiles. It was only later that I realised, mainly due to bare feet on them, that it was vinyl sheeting. Perhaps another easier and cheaper way to go.

Paul

[stella]

If  the  floor  moves/bounces  at all,  then  so  will  the  tile, then  crack. Large  tiles  will  crack faster than  smaller  tiles...but  to  do it  right  pull  up  the wood floor and  pour  cement  or use a  cement  type  of  floor  board.  Or  build  up the floor  to make a step into the  bathroom ??

[frexpt]

[quote user="stella"]If  the  floor  moves/bounces  at all,  then  so  will  the  tile, then  crack.  Large  tiles  will  crack faster than  smaller  tiles...but  to  do it  right  pull  up  the wood floor and  pour  cement  or use a  cement  type  of  floor  board.  Or  build  up the floor  to make a step into the  bathroom ??
[/quote]

We have already bought the ceramic tiles for this upstairs room, so would like to find a way of using them, although we are happy to look at whatever adaptations might need to be made.  There is no question of cutting corners with this property just to save a few Euros.  We also enjoy the luxury of not having to live in the property whilst work is being done, so if it takes a little longer, that is not a problem.

The house is divided vertically into the original part, dating from 1900, with a newer two storey extension at the rear.  From the outside it is difficult to distinguish between the two phases of building, as they are well matched.  The internal floors of the older part are old oak boards and we were not expecting to find something as new as Placosol when we took up the laminate in the "newer phase".  I'm guessing that the age of the extension (or at least the fitting out of it) must be much more recent than we anticpated, probably 2000 - 2002.  A trip to the Mairie next week might clarify matters.

Anyway, it occurs to me that Placosol must be rigid, as by its nature, one would expect a plaster based product to break up internally if there was any give in the boards, given the amount of foot traffic it would have endured over 8 - 10 years.  There is no evidence of that, the boards look and feel perfect.

Given that the entire first floor area of the extension was fitted out with the same laminate, it is reasonable to expect to find Placosol throughout.  As all the laminate will be taken up eventually, I think the way forward will be to raise the entire floor level with plywood (maybe of varying thicknesses), then put down whatever floor covering we decide on, but maintaining a consistent level.  So far as the present bathroom is concerned, I like the look of the Schluter product to add a further layer of waterproofing.

Many thanks for all of the replies.........[B]

[Théière]

Frexpt, working from a google translation only placasol is a high density plasterboard without a vapour barrier and only 13mm thick, so in my world if would have to go. There was a Belgian or was it a Dutch lady on the forum a while back who was looking for a specific product which was a corrugated steel that had a cement leveling type compound applied prior to tiling, that was quite thin in section.

[frexpt]

Just come back to look at this job again after feeling grotty with a virus for a few weeks.  I've cut through the Placoboard with a hole saw in a corner of the room and discovered that it is actrually two layers, so is 26mm thick and laid onto the joists.  I'm satisfied with the rigidity of the floor, but will add a moisture barrier of some sort.  I did find the post by the Belgian lady and the link to the system she was championing, which looks to be just the job.........

[WJT]

Hi, we have just had to have a newly tiled floor taken up because of movement. I am certainly no expert but because of having to go through this I have sadly learned a lot as well as having to take advice. I would say that if the floor is plasterboard you would have a problem.

Unfortunately the plumber cut channels through our floorboards to run pipes so had to take the floor boards up. Upon having to rip the first attempt out that was done by a tiler it was advised to use two levels of tongue and groove OSB boards minimum 22 mm each layer running in different directions. However our floor is 3 meter wide by 3.5 meters long on beams that have movement. So perhaps depending on the size of your floor space the 22 mm thickness (x2) may not be necessary.

But in any case after my experience I would highly advice you not to use plasterboard as a substrate. The Ditra mating in addition to waterproofing also acts as a decoupler for the tiles. So they will be less likely to crack if they are laid on top of the mat versus directly on the wood.

Ours was just finished this week, so fingers crossed it will work!

What are the dimensions of your floor?

[Théière]

WJT, did they use flexible adhesive and grout on the original tiling?

[WJT]

Hi Theiere, yes it was flexible glue and grout. It is difficult to describe what he did but he put boards between the beams and filled up with cement mixed with polystyrene balls called chape leger. So the structure was part of the floor versus being on top of the beams. The floor dropped by about an inch and there was a diagonal crack running through the tiles. Funnily enough the flexible grout was fine, the crack ran right through the 40 x 40 cm 12 mm thick tiles.

[frexpt]

[quote user="WJT"]

What are the dimensions of your floor?

[/quote]

The room is roughly 4 x 3, but after installation of shower cubicle, bath, WHB and WC, there will really only be a central "corridor" that will take the traffic and that is obviously a concern.

The builder we have used on and off for the past 8 years has had a look and he doesn't see a problem with tiling onto the plasterboard, provided flexible grout is used.  However, we are unlikely to do much more with this before the New Year, so maybe in that time we'll decide to go belt & braces and lay an additonal layer of plywood.

[NuBeginnings]

Schluter Ditra is great stuff, have used it a couple of times when installing a wet room my tiler swears by it.