Floor tiles adhered using dot and dab technique???

[Mutley56]

Hi all,

I have just had the bathroom floor tile grout replaced today as the original was cracking up after only 4 months. The plumber who put the floor down 4 months ago didn't do a very good job and so I askded him to regrout it. He did, but did not remove all of the original grout and so the new grout has cracked up already - no surprises there!

I've got a professional tiler to remove all the grout today and regrout the entire floor. He suspects that the plumber has dot and dabbed adhesive in certain places under some tiles and spread adhesive under others.

Can anyone of you helpful people let me know whether it is good practice to put large porcelain floor tiles down by using dots and dabs of adhesive? The tiles are overlying plyboard screwed down every 6 inches into suspended timber floor boards.

Thank you for taking the time to reply.

Mutley56

 

[Richard C]

Floor tiles must be laid on a continuous bed of adhesive but this in itself may not be the reason for the grout cracking. It seems you have a degree of movement in the floor which the grout cannot cope with, are the cracks appearing all over or just in a certain place?

It’s also very important to use high quality trade, flexible adhesive & grout on these floors, cheap DIY products usually give disappointing results. It’s also vital that the floor is as ridged as possible; how big is the floor area, how thick is the ply over boarding, what type is it & exactly how was it fixed down, i.e. through the boards into the joists below or just screwed into the boards? Any joins in the boards & where are they located

 

[Mutley56]

Thank you for your prompt reply Richard C,

You've given me a lot to think about in your reply. As far as I'm aware, 12mm plyboard was used. I assume the screws use were of adequate size and driven into the timber joists.

I know the adhesive was a good quality flexiable powdered variety as I purchased it along with the BAL flexible wide joint grout powder and tiles from a tiling warehouse.

The cracks were in one area of the floor and I suspect that there was a problem with spreading the adhesive evenly (although I can't imaine why) and / or the underlying floor is not as rigid as it could be. The tiler suggested that more jobs are carried out these days using hardebacker board (that's what I think he called it) rather then plyboard.

Anyway, the floor looks great today, grout sealant being applied tommorrow and I'll have to adopt watchful waiting to see if the problem recurs. If it does, then I'll have to take up the floorng and restart the whole job with new tiles etc and a professional tiler.

Thanks again for showing interest in my problem.

Mutley56

 

[Richard C]

I know the adhesive was a good quality flexiable powdered variety as I purchased it along with the BAL flexible wide joint grout powder and tiles from a tiling warehouse.

Nothing wrong with BAL, it’s all I ever use.

The tiler suggested that more jobs are carried out these days using hardebacker board (that's what I think he called it) rather then plyboard.

I’m not sure I would agree with that; tile backer boards have their uses, particularly for over boarding & I always use them on stud walls in wet areas but they are rather expensive. My personal preference is always to replace floors rather than overboard if I can, in which case I always use a minimum 18mm WBP plywood but in some cases it needs to be 25mm thick.

Anyway, the floor looks great today, grout sealant being applied tommorrow and I'll have to adopt watchful waiting to see if the problem recurs. If it does, then I'll have to take up the floorng and restart the whole job with new tiles etc and a professional tiler.

As you say best thing to do is suck it & see, you’ve nothing to loose. As with any trade there are good & not so good, you cant afford to skimp on preparing wooden floors for tiling & it’s false economy to use nothing but the best materials.

 

[Mutley56]

Thanks again Richard C,

I read with great interest your opinon about the use of 18mm or even 25mm plyboard over the suspended timber floor boards. I've only got 12mm plyboard in place at the moment.

If a tile did became loose because of the suspected dot & dat approach to adhesive adopted by the plumber in the first place, how feasible would it be to remove the one affected tile, put down a spare one on a even bed of flexible adhesive and then grout the joints around the replacement tile?

I wonder what the outcome of that project might be? Clearly the grouting would not be continuous with the exiting grout around the other tiles, and I wonder how this would affect the overall look / function of the floor?

I suspect that there are a host of other problems that have not occured to me and I would be grateful if anyone could let me know of the frequently occuring problems that may result from this course of action?

Thanks once again for your time taken to read and reply.

Mutley56

 

[Richard C]

I read with great interest your opinon about the use of 18mm or even 25mm plyboard over the suspended timber floor boards. I've only got 12mm plyboard in place at the moment.

I didn’t say I used 18/25mm over for over boarding, this thickness I use when replacing the original floor. If I have to over board, I use 12mm; this is really the minimum you should use but even that will give a raised threshold that many folks won’t accept.

If a tile did became loose because of the suspected dot & dat approach to adhesive adopted by the plumber in the first place, how feasible would it be to remove the one affected tile, put down a spare one on a even bed of flexible adhesive and then grout the joints around the replacement tile?

If you can get the tile up without damaging it’s neighbours it should be possible but unless the tile has physically become loose, I don’t think that’s your problem; as I said previously, I believe you have movement.

I wonder what the outcome of that project might be? Clearly the grouting would not be continuous with the exiting grout around the other tiles, and I wonder how this would affect the overall look / function of the floor?

If you use grout from the original bag, it should be a perfect match & almost invisible but what it will look like will depend on how good a job is made of it. Someone who is looking for it with a trained eye will usually spot it but unless you know it’s there, most probably wouldn’t notice it.

I suspect that there are a host of other problems that have not occured to me and I would be grateful if anyone could let me know of the frequently occuring problems that may result from this course of action?

If the problem is being caused by excessive flex in the floor, most likely it will always crack again.

 

[jefoss]

you say you bought flexi adh, just a thought, did you see what you bought being used?

 

[Mutley56]

Thanks again for your thoughts Richard C and jeffos,

Richard, I now understand about plyboard thickness. I will see what happens with the floor, and if movement disturbs a tile or two then I will see about replacing them. If the problem was to re-occur after that then I'll bite the bullet and have the entire floor replaced by a professional tiler.

jefoss, I didn't see if the plumber had used the flexible adhesive that I supplied for his use, but I hope that he didn't take that away and use an inferior product on my floor! I guess that I'll never know for sure.

Thanks again to both of you for your interest and valuable advice.

Mutley56