Mapei ultracolour plus is it supposed to be flexible? Disaster strikes :(

[Notts]

Firstly hello all, just joined the forum as I've had a disaster and am hoping someone can help.

I've tried googling this and searching the forum but I can't find much (maybe I'm doing it wrong?) so here goes.

About 6 months ago I tiled my sisters bathroom using large real stone (I think) tiles. The bathroom is upstairs and on a wooden floor, so she got a reputable guy to do sort the floor with plywood before I layed the tiles.

I went to the local tile wholesaler showed them an example of the tiles to be layed and explained the situation (upstairs, ply floor etc etc). For which they gave me adhesive and Mapei ultracolour plus grout.

Anyway everything was fine until after about 2 months of the tiles being layed when the grout started breaking up I was away and by the time I returned 6 months had passed and the grout in all the areas that are walked on the most is breaking up really badly.

The floor does have a very slight spring to it if you bounce your weight up and down but this is only visible to someone standing a few feet away and watching you bounce up and down (to the person bouncing it feels very solid).

Also I've removed a few chunks of the grout and it is hard and brittle and does not appear flexible at all? Nor does it say anywhere on the bag "flexible" just ultracolour plus/bioblock/drop effect etc etc.

Can anyone advise what the problem is likely to be? Is it the grout or something completely different?

Regards

David

 

[grumpygrouter]

The issue is the bounce in the floor. This should have been rectified before installing the tiles. Your grout is a highly modified flexible grout but it will not flex sufficiently to allow that sort of movement. Also the stone tiles will be very heavy adding extra loading to the floor. No easy fix I am afraid, sorry.

 

[Gazzer]

The substrate is the problem. If you have deflection then you need to sort that out 1st. You say the floor was plyed before you tiled but with what thickness and method.

 

[Notts]

Hi, huge thanks for the quick replies.

With regards to the floor question:

First he laid stips of wood on top of the old floor at 14" centres then put 12mm ply on top and then put in what seemed like about a million screws. I'd not thought to question it at all as he came recommended because he's done the same for several of my sisters friends over the years, as well as a lot of other joinery work.

 

[Gazzer]

But deflection is deflection and the most of the time the 1st thing to give will be the grout.

 

[Gazzer]

What stone have you used ? What adhesives did you use and what other preparations did you make ?
How large an area of room are we talking about ?
Its very unlike Mapei grout to exhibit the symptoms that you describe.
Was an expansion joint left around the perimeter of the room ?

So many questions due to being so many possibilities , we need to know the full story.

12mm ply is not BS should have been min 15mm to be technically correct.

 

[Notts]

What stone have you used ?

My mistake, Slate effect porcelin around 13" square and about 10mm thick.

Getting old, memory ain't what it used to be, what day is it again etc etc

What adhesives did you use and what other preparations did you make ??

PCI Timberflex 2 part.

Floor clean, free of dust.

How large an area of room are we talking about ?

Approximately 3m square

Was an expansion joint left around the perimeter of the room?

Yes.

12mm ply is not BS should have been min 15mm to be technically correct.

Is that likely to cause problems? Will have a look in her shed as there are quite a few scrap bits that I can measure to make sure.

Hope that helps, and thanks again for the help.

 

[Notts]

Got her to measure the scrap bits and yes it's 12mm.

 

[Gazzer]

The deflection will be the cause. As you said Stone I was wondering why the stone hadn't cracked 1st. Now yo say porcelain it all makes sense. Deffo deflection issues IMO.

 

[White Room]

You say that wood strips were put down then the ply laid on top, was there a gap between the ply and the floorboards due to the strips being laid..