Crumbling Grout

[alexh75]

Hi All
We had a new bathroom fitted in December last year. Very pleased with it in general, but having huge problems with the floor grouting. It's only a small floor area (4ftx5ft), and we noticed the grout crumbling (but only in certain areas, generally those with the most traffic), around about January. We've just had the tilers back to re-grout the affected areas, but 3 days later it's all starting to crumble again. The floor seems to be rigid enough, and I can't detect any tile movement. When you tap the tiles you don't get a hollow sound, everything sounds quite firm.

Total floor area tiled is 4ftx5ft, affected area is generally in the middle of the floor, around 2ftx2ft.
Original floor is timber floorboards. These were very sound and had no discernible flex.
We used No More Ply backer board as per manufacturers spec, screwed down correctly and staggered. There is underfloor heating, this is laid and secured on top of the No More Ply. A self levelling screed was also used.
Flexible tile adhesive and Unibond flexible grout .

What to do?

Many thanks
Alex

 

[Richard C]

Unibond flexible grout .

There’s your problem; I don’t know any trade tiler that would be caught dead using that stuff.

What to do?

Difficult to put right now it’s all laid but you may get away with raking & re-grouting using a decent trade product.

 

[jctilingservices]

Richards answer was spot on for you mate, both parts

or

it is possible that there is slight movement in the floor around your traffic area, just enough to force the grout away from the edges of the tiles BUT i would be more inclined to go with Richards answer

 

[lancenotalot]

Try a flexible additive in your grout as this tends to give more flexion than actual powdered flexi grout.

 

[tictic]

just out of interest...how big is your grout spacing?

 

[alexh75]

thanks for all your replies folks

i have been looking at the bal range of grouts which appear to be quite highly thought of.
looking at the microcolour range with admix GT1 additive or is it worth using something like easypoxy?
it is quite possible that there is a wee bit of flex in the central area of the floor that is pushing the grout out slightly, but I would have thought that a decent flexible grout replacement would be designed for situations like this.
grout lines look around 4mm and the flexible grout replacement would need to be in grey. Any further suggestions welcome.

Cheers
Alex

 

[alexh75]

Hi guys
Any recommendations on a good flexible floor grout available in grey? Is Bal OK? Traditional grout or epoxy?
Many thanks
Alex

 

[Richard C]

I use this extensively but on well supported floors;
http://www.bal-adhesives.co.uk/products/microflex-wide-joint
take note of JCT’s post & your admission of “slight flex”; if there is more than discernable flex, it could still give problems, even with the adhesive eventually.

Easypoxy is primarily designed for use in hygiene situations, kitchens/hospitals etc. where an impervious waterproof finish is required, I’m unsure if I will tollerate any additional flex; Superflex might serve you better.
http://www.bal-adhesives.co.uk/products/superflex-wide-joint

 

[alexh75]

Thanks Richard
I think I will give the Bal Superflex Wide Joint a go as this seems to be the best match for what I need. If the problems re-occur then we'll have to look at re-laying, but we'll cross that bridge if we come to it.
Cheers
Alex