Slate tiles not sticking down

[Chris Blackwell]

Thanks everyone for your input, its appreciated

@Knackered Knees - The advice i was given by the tile supplier was to use an SBR slurry on the backs of the tiles. My understanding was that the SBR wouldn't adhere well to a wet tile (SBR being a rubber compound). Also i see your point about wiping the dust off, however the liberal coating of SBR was more than enough to take care of the dust on the tiles as they weren't massively dusty.

I guess the "why" is sort of academic, lesson learned; ask for advice before not help afterwards! 😉

It may be the case as Jay said that the best option would be to lift and relay them, but would anyone care to offer an alternative, or pass comment on re-bedding them on a slurry? To be clear this is my patio, and i'm not a tiler, just a diy-er, so if i can avoid relaying them that is completely preferable!

thanks again

 

[White Room]

Do you have solid coverage under the slate with the sand/cement.

 

[Chris Blackwell]

Do you have solid coverage under the slate with the sand/cement.

Yes, i'd say 90% or better coverage on all the tiles

 

[DHTiling]

The slurry coat method is more for work on dry pack laying.. imo as it gets a better hold, i think the wet bed has hindered the bond with the slurry coat.

If the bed is solid and well adhered as you say, then stick the tiles back down with Adhesive..

 

[Chris Blackwell]

If the bed is solid and well adhered as you say, then stick the tiles back down with Adhesive..

That does seem like the best solution. I couldn't use adhesive originally as there was too much variation in the levels on the concrete, but if i lift the tiles and treat the mortar like a screed, then i should be able to relay onto that without too much difficulty.

So before i do that what should i do to prep the mortar and tiles, and what adhesive should i use?

I'm guessing i should wait until the mortar is a week or two old so that its nice and solid and then it'll need sealing, but what with?

 

[paul damian]

Chris next time youre mixing sand and cement and using it to bed tiles do not use plasticizer, mix it a bit wetter to get it workable. The slurry mix has gone off but the mortar bed hasnt because off the added plasticizer .

 

[Spud]

I have fitted loads of stone and tiles with this method, you didnt even really need the sbr bond in the slurry in this circumstance the supplier gave this advice as overkill ,the slurry needs to be creamy inconsistency if its too wet it doesnt give a good bond to the sand and cement also the sand and cement bed must bed semi dry like floor screed if its too wet or too dry you can get problems, the only other issue is the compaction of the bed under the stone, sometimes when fitting, you can hit one side down too far then tap the opposite side to bring the tile level causing the tile to see saw on the bed this will cause the tile to come loose as only a small part of the underside of the tile is in contact with the bed and a void is formed, when fitting work this method we tap the work with a hard wood stick to see if they were fully bonded any voids were flood grouted the following day which makes the floor completely solid, this method is by far the best method for this job, as Dave says now every thing is dry just take the loose ones out and restick with adhesive grout them with flexible grout and the job will by fine

 

[steve187]

In the old days ( yes i know) before adhesives, if laying quarry tiles on a thickish bed we would use a semi dry mix that just forms the shape of your hand when squeezed of sharp sand and cement, we would then put a thin slurry of neat cement, on the surface of the screed and lay the quarries onto the screed, once a metre wide strip was laid we would then beat the surface of the quarries with a 6-8 inch length of 4x2 timber until they were all level.
if a thin bed of screed was required we would mix wet and the as knackered knees said sprinkle a neat layer of dry cement to the screed , then lay the quarries and use the 4x2 again.

In answer to you dilemma i would suggest taking up the slate and using a suitable outside adhesive to relay on the remaining bed of sand and cement as long as it is sound, as suggested by others

 

[White Room]

Surley adding less plasticizer would do the trick.

 

[BethanyHope]

Did you find a solution to the slate not bonding to the bed? I'm having the same issue...added PVA to this mix, 3rd time around! Only did one part of the repeating pattern to test it out but I'm fed up with the waste of materials now!