tiles not sticking

[threaders]

Help desperately needed...

I am tiling a shower room and having a spot of bother. I am using 300 x 400 ceramic tiles laid in a brickwork pattern, and am using unibond pre-mixed "tile on walls" adhesive / grout. It seems to have held the first couple of rows ok, but on an adjacent painted wall the tile were still loose after 24 hours. It looks like there is a problem with the adhesive not going off - it has a powdery type consistency.

Any ideas? I am not 100% confident that when I install the shower that the tile will stay on the wall. What is the best (strongest) type of adhesive to use? I followed the guidance and used pva to seal the walls first - however having read the forum notes I am beginning to think that was not wise.

You help is massively needed please.

Cheers.

[royaloakcarpentry]

The tiles are too big for tubbed adhesive, they need to be fixed with a bagged adhesive which you mix yourself. The tubbed adhesive dries on air contact and therefore with the size of those tiles there is not enough air getting to the adhesive to set it.

Also if you apply too big an area of the adhesive then it starts to go off before you apply tiles.

The painted wall you need to do a paint test to see if it is suitable to prime and tile straight onto. To test, apply a few strips of gaffer tape, leave it for an hour or so and then pull off. If the paint comes away with it then you need to strip paint from wall. If paint remains on wall when pulling tape off, then prime and tile.

PVA is not an ideal primer for tiling onto. Although if Unibond said to use it, then who am I to dispute them. PVA can lead to failure of adhesive to bond to the wall.

I would take off the tiles. Buy a bagged adhesive such as Bal, Nicobond, mapei and use the primer from the manufacturer of the tile adhesive. bagged adhesives are nothing to be frightened of using. they have a long working time once mixed, spread easier than tubbed.

use a minimum 2.5mm tile spacer with those tiles.

[threaders]

Thanks for that.

I have used 2mm spacers and generally put 2 or 3 tiles on at a time, but will take your advice and check the first courses. I have never mixed powdered adhesive - what sort of quantity and what sort of consistency do you generally work with?

By the way when the tiles came away from the painted wall, the paint became very easy to peel off - in fact it came off in plastic type sheets, so I am assuming that its not best ever as a tiling surface.

[Simon Site Manager]

Hi Threaders,

I normally 'knock up' in a 2.5 litre plastic paint kettle, filling about 1 third with powder, that's 'cos I'm slow and it's my house so can take my time. Wants to be the consistency of how you would make polyfilla or cake mixture, smooth and creamy so that it will stick to your trowel and not slide off!

S

[royaloakcarpentry]

I normally use my builders buckets but that is because it isn't going anywhere near my plastering ones lol.

It will give you the ratios on the bag, I dare say it varies on what make it is.

You need to take the paint off. In reality it is the paint that is holding the tiles and not the wall, that is why a paint test is done. The paint test just confirms whether or not it is itself adhered to the wall and capable of transfering the tiles weight onto the wall. Yours clearly is not. Extra work for you.

better change your username to 'completelythreaders'

[barney_123]

Well I think I'm the UltimateMuppetMan as after reading advice here I also think I'm doing everything wrong.
My first mistake - I asked the guy in the tile shop how to prime / seal the walls before tiling. He recommended PVA. So I cover the walls in PVA and later read that some adhesive is incompatible to PVA - so I buy the ready made adhesive (Unibond) that also recommends PVA prime.
Wanting to know how long it takes to set properly I've been reading your thread. My tiles are porcelain 60x30cm and have been on for 48h. I've been getting really worried that I'll have to do it all over again including stud walls. I've been trying to "test" the firmness of tiles I fitted 48h ago and I cannot budge them despite pulling really hard. As I have this positive to draw on I am inclined to keep the room warm for a week or two and put a dehumidifier in there before grouting.
Am I living in denial? Do I really have to rip everything off and start again...

[royaloakcarpentry]

If they have stuck then leave them as they are.

Primer as previously pointed out should be as per adhesive manufacturer instructions, so PVA is fine for unibond. Infact I would imagine most DIY adhesives will use a PVA for priming.

Don't use dehumidifier. Just follow instructions on grouting. It may well be 5 days from tiling until you can grout.

[barney_123]

thanks - much appreciated. At the rate I work 5 days will be a cinch. Maybe start on the kitchen...

[threaders]

Cheers for the advice on here. I ended up taking the tiles off altogether and I put some bal primer (strange blue colour) on the walls. Went out and bought some powdered granfix adhesive, mixed it with a drill thing and put the first 2 rows of tiles up. Great result - would take a herculean effort to get the things off the wall. The only down-side is that the stuff went off in the bucket after only 20 minutes.... Got a bucket shaped lump of adhesive in the garden now... At this rate I will have a new rockery in the garden unless I can sort the consistency out. I think I need to work with a thinner consistency tomorrow. Any tips from the top?

[marc1106]

Cheers for the advice on here. I ended up taking the tiles off altogether and I put some bal primer (strange blue colour) on the walls. Went out and bought some powdered granfix adhesive, mixed it with a drill thing and put the first 2 rows of tiles up. Great result - would take a herculean effort to get the things off the wall. The only down-side is that the stuff went off in the bucket after only 20 minutes.... Got a bucket shaped lump of adhesive in the garden now... At this rate I will have a new rockery in the garden unless I can sort the consistency out. I think I need to work with a thinner consistency tomorrow. Any tips from the top?

sounds like you got a rapidset addy nothing to do with consistency! see if granfix do a standard(slow) setting addy!

oh and make sure you dont whisk it to fast, better to keep the drill under 600rpms

[threaders]

I will check the bag - I have a feeling it may be the rapid set stuff. Is there any mileage in mixing it a bit thinner to get more than 20 minutes out of a mix?

[Jaeger_S2k]

No, It'll just be sloppy. Mix smaller amounts if your not in a hurry and rapid doesn't like being beaten. Then again you shouldn't beat any of them too fast, as marc says.

I would agree that you may find it easier and less stressful to get a normal set.

[barney_123]

I've been thinking some more about my apparent good fortune in that the tiles have stuck despite them being too large for the adhesive. I've come to the conclusion that it might be my stud wall that has come to my rescue. My reasoning is that the tile adhesive is actually drying from the other side and so the extra ventilation behind is doing the job.
That has given me reasurance to some extent. Also - thinking about when it's fully dry and ready to grout - well the Unibond adhesive has a distinctive smell so I figure, when I can't smell it anymore then it is fully dry.