Why is Unibond adhesive still "damp"

[zanwan]

Hi

I've been tiling at the weekend, using thin 20x25 cm tiles, and Unibonb Mould resistant adhesive i brought from BnQ. I went back to the bathroom yesterday and tugged one of the tiles and it came of the wall, with very little effort. I tried the same to a few more and the same thing happened! The adhesive, after 2 days, still didnt seem fully dry, it seemed mildly damp.

Is this normal? Does it take a while for this adhesive to dry?

 

[tictic]

dont take this the wrong way mate...

uniBomb..is crap adhesive bud....how long it takes to dry.."how long is a peice off string"...

strip the tiles from the wall,scrape the crap off and the wall(shouldnt be to hard)..and get a decent adhesive.

 

[zanwan]

what adhesive would you recommend?

 

[Richard C]

Cos it’s total & utter crap. Always use a quality trade tiling materials not DIY rubbish; BAL, Mapei (but not the B&Q stuff) Webber + some others. You should also be using a cement powder adhesive on that size tile not tub mix, it’ll never dry as you’ve found out & I think you likely to end up stripping & starting again.

Where are you tiling & what are you tiling onto?

 

[zanwan]

Oh god dont say it wont ever dry! The effort i've put into tiling this! Lukily i've only tiled upto the border (halfway) so far. So from now on will tile all the way upto the top using quality adhesive.

Would you recommend bal ready mixed adshesives or should i stick to powderd stuf?

I'm tiling in the bathroom, onto solid wall, covered in plaster. Plaster is years old so no issues with that.

Surely if this unibond stuff is as bad as you say, people would be suing them left right and centre?

 

[Richard C]

Oh god dont say it wont ever dry! The effort i've put into tiling this! Lukily i've only tiled upto the border (halfway) so far. So from now on will tile all the way upto the top using quality adhesive.

We get this on here time after time; many try persevering with it, heaters & god knows what, we don’t hear from many of them again but a couple have come back to say in the end they had no alternative but to strip them off & start again; in one case the tiles actually started falling off the wall. Personally I’d strip them off while you’re still easily able to & start again using the correct materials & if it’s in a wet area even more so.

Would you recommend bal ready mixed adshesives or should i stick to powderd stuf?
I'm tiling in the bathroom, onto solid wall, covered in plaster. Plaster is years old so no issues with that.

BAL ready mix is very good stuff but, as I said before, you should really be using a cement powder adhesive on that size/weight of tile not tub mix. Tub mix relies on evaporation to set & the sheer size of the tiles prevents evaporation, hence tub addy can take an age to go off to the point where it can be grouted. Powder cement addy relies on chemical cure & does not need evaporation to set, it can be grouted the next day & in some cases after 4 hours.

If you do use powder addy, you must prime gypsum plaster & plasterboard to avoid the possibility of reaction between the cement & gypsum.

Surely if this unibond stuff is as bad as you say, people would be suing them left right and centre?

The tub mix is probably OK for cheap/light 4 x 4 tiles but that’s about all it’s good for. Do yourself a favour, before you go any further read the Tiling Sticky & Tiling Forum archive posts, it may prevent you from making more & potentially expensive mistakes. Come back if you have more questions. Are you also tiling the floor?

 

[zanwan]

thanks for the advice, will take on board your comments.

I've not yet grouted the walls, and as i'm only able to work on this project in evenings, the householder is happy to leave the tiles for a while and see if the adhesive dries, he doesnt want me to strip of again and its going to take ages to get the bathroom done.

I will be tiling the floor, but i'm using powdered cement for that.

Also just to add, the tiles are 20 x 25cm, 7mm thick, they feel very light.

 

[Richard C]

I will be tiling the floor, but i'm using powdered cement for that.

What are you tiling onto, concrete or suspended timber floor? if it's timber, what sort is it & what prep are you doing?

 

[zanwan]

its concrete floor. Its been covered in vinyl floor tiles, which i have removed most off. would i need to remove the black glue?

 

[Richard C]

Is the back glue bitumen based? how well is it stuck down? Is it level?

 

[zanwan]

it is level and does appear to be well stuck down.

Also when you mentioned i need to prime the walls before using cement based adhesive, would this be done using PVA? Or would PVA not be suitable where a shower is to be installed?

 

[Richard C]

it is level and does appear to be well stuck down. ?

If its bitumen based adhesive, tiling over it can be tricky & is not recommended or guaranteed by most of the adhesive manufacturers. The problem is that the stuff is almost impossible to remove by mechanical means (it just goes soft) & solvents are not practical for health reasons & will almost certainly risk a reaction or poor bond with the adhesive. Two possible solutions taken from another thread, one mine;

• Remove the thicker/uneven/loose bits, make sure it’s clean & no grease, prime with an decent SBR based bonding primer & tile using a flexible cement powder adhesive (Rapidset Flexible). Neither I nor the adhesive manufacturer will guarantee it but I’ve tiled onto a couple of old kitchen floors without any comebacks. Some recommend priming with Ardex P82 primer but I’ve never tried it; only bullet proof approach would be to put down a self leveling screed & then tile over that.

& one from another regular & respected contributor;
• scrape off as much as you can off, then put a slurry coat over it 2 parts Portland cement and 1 part SBR.

Also when you mentioned i need to prime the walls before using cement based adhesive, would this be done using PVA? Or would PVA not be suitable where a shower is to be installed?

Never use standard PVA a tiling primer, its water soluble, affects tile adhesion & if used in a shower (wet) area, your tiles may well end up on the floor. Use an SBR or an acrylic based primer.

 

[zanwan]

Hi Richard

Many thanks for your reply, its much appreciated and is proving very helpful.

I will try and remove as much of the bitumen based adhesive as i can, and then put some acrylic based primer.

Just another question. Its very cold in the midlands at the moment, reaching 0 at the moment at night. Is it best to wait for the temperature to rise a bit or is it safe to tile in these cold temps? The bathroom has a radiator but the room never really gets very warm.

regards

Naz

 

[Richard C]

I would stick some cement in it to make a slurry as suggested & prime with that.

Do not tile in temperatures below 5 degrees or if likely to drop below that within 24 hours. If the property is heated, even if the room itself isn't, I doubt if the ambient temperature would drop to anywhere near that. Do not tile in damp conditions. Critical you use only a quality powder adhesive (flexible in this case) & flexible grout, do not be tempted by cheap DIY shed stuff. I would use BAL Rapidset Flexible but there are others equally as good.

 

[tictic]

if you can get your hands on a heat gun or similar then get heat onto the "tar" then using a spade scrape as much you can..
then slurry coat and tile addy as soon AS YOU CAN...or just use a 2 part LATEX based compound over it...F Ball ones for me.