Is this a case of concrete still wet?

[Martino]

I recently went and quoted for a 20m2 kitchen floor..i will be fitting 600mm x 600mm porcelain. the customer took up the old tiles and he said they came up really really easy. it was tiled the same year the house was built. could they have came up so easy because the concrete was not fully dry or some other reason?....I have never had to prime concrete before applying the adhesive is this something i should consider? before i lay the new tiles..the house is around 10-15years old now.

 

[White Room]

I would prime before fixing but is it a standard sand/cement screed....

 

[Ajax123]

With concrete you are more likely to have issues with it being too dry. If yo don't prime it and its too dry it will suck the moisture out of the adhesive before it has time to set properly.

Couple of questions... Are you sure it is ordinary concrete. Secondly can you describe (or better still post pics) the adhesive under the failed tiles e.g. Wet, powdery, soft, hard and stuck to the tiles etc etc....

 

[bugs183]

Could be alsorts of reasons.
No one primed floors back then, so it could just have been dusty, or it could just be duff adhesive etc.
These days priming is advised and it really does help the performance of the adhesive, just follow the manufacturers instructions.
How flat is the floor, it may need a topping of levelling to get it good enough for 600x600's in which case certainly prime the floor before levelling, it makes a huge difference to how well it levels and bonds.

 

[Martino]

its basic sand and cement with pebbles but its pretty flat to be fair....could anyone reccomend a decent primer? could you just use pva for a floor. i no its not advised for a wall but a floor?

 

[Ajax123]

Not Pva. Use a standard acrylic primer there are dozens available e.g. Ardex p51 or bal APD etc etc. try to use adhesive from the same manufacturer of the primer as well.

 

[Martino]

Cheers for that ajax i have a feeling its probs going to be mapei as i think they tiles are from b n q but ill have to wait and see cheers pal

 

[bugs183]

Ooh be careful with B&Q tiles, i'd shop around a bit as you may be getting low quality tiles for your money.
As Ajax says (he's our screed guru!) never use PVA, if your using Mapei then their Primer G will do fine, i apply it with a pump plant sparayer, much easier way to prime larger areas.

 

[DHTiling]

If a screed is dusty , then yes sweeping and priming is the way but not all screeds need priming .. burning in the adhesive will create a good key..

 

[Ajax123]

Ooh be careful with B&Q tiles, i'd shop around a bit as you may be getting low quality tiles for your money.
As Ajax says (he's our screed guru!) never use PVA, if your using Mapei then their Primer G will do fine, i apply it with a pump plant sparayer, much easier way to prime larger areas.

Hmm that's interesting as I was always told primer should never be sprayed... Brush or roller as this works it into the screed surface.

Quick question off topic... Do many tilers spray the primer?? Reason I ask is that I come across loads of tile failures where the primer has failed to penetrate into the screed so it doesn't hang on very well?? Might answer a question


as for b and q .... They do a nice range of porcelaine that can double up as salad bowls....

 

[DHTiling]

I brush primer in .... maybe a new thread and a POLL would be better..

 

[White Room]

Brush or roller for me, never sprayed it on.....

 

[Ajax123]

I brush primer in .... maybe a new thread and a POLL would be better..

Agreed. No idea how to set u a poll but agreed....

 

[Rookery]

Roller for me. Its never occured to me to spray it on.

 

[bugs183]

It's a fair point about spraying and whether it is better than brushing or rollering, Mapei say you can:
http://www.lilleytileandstone.co.uk/sites/default/files/PrimerG_UK.pdf

I've never had any issues spraying, but as you say it would take no time to apply with a sprayer and then rollering over to be certain.