12mm slate tile patio possible problem

[mugginstoo]

I am having an 8-12 mm thick slate tile patio laid outside. The landscaper has used a sand and cement base then brushed a PVA solution on the back of the tiles and tapped down. It is 6 days since he laid the first tile and they have not adhered to the base.
He is telling me once he's grouted it'll all be bonded. He says I mustn't walk on the patio or touch the tiles or I'll ruin the bonding which will happen as it all dries. My research seems to say a product called Bond it PVA based can be used with cement but not in damp situations.
I've never laid a patio, but I did research the tiles I bought, ( the landscaper did not specify or advise, I did say if no good can send back) the chap laying also used a sand and cement base but he troweled a 1:1 sand cement very wet slurry on the back of the tiles before bedding/ tapping in. I do not know whether that was a successful bond as it was only a video.
I need advise, will it all be ok as my landscaper says or are my fears correct? I did raise my concerns at the beginning but they seem to have been ignored. Would I be best to have the row ASAP before he grouts?
What will happen if the tiles don't stick down? It is a large patio of 50m2?
Also sealing advise. My research suggests it is best to seal the tiles before grouting but again my landscaper has said no this is wrong it must be done when everything has dried and settled, best a month or so after laying. Is this really true?
It seems rude to say to the supposed professional, sign painted vehicle and references from 2 neighbours how to do his job so please let me know what I should do.

Thank you

 

[cannonfoder]

any chance of a pic please as if its natural slate you should sea the tops before laying. grouting in the slates wont fix your problem at all all it will do is is lock them together soo to speak but if there loose or rocking the grout will just crack an pop over time an winter will kill it.

you can lay them on a sharp sand an cement screed base lean mix but yiu have to bond the backs with something like a SBR and OPC slirry mix.

Or you can even lay them on top of a concrete base or old paved patio as a over lay with a tile stone adhesive


https://www.youtube.com/watch?v=EabZ5-XDjZ0

have a look at the link your like it

 

[r896neo]

Slate flags could be laid on a mortar base but anything less than 20mm is not a flag in my opinion.

Tiles should be laid with proper tile adhesive over a pre-prepared concrete base Which has been allowed to dry.

If these were flags i think his method is fine but not for tiles.

As cannon says ideally the flags would be laid with a bonding slurry painted on the back.

He is right about the sealer. Everything needs to be totally dry before sealing so unless they are presealed in a warehouse it needs to be done after.

Who supplied the tiles and what base do they recommend, furthermore has your landscaper ever laid these before on this type of base? and i don't mean slate flags which are 20mm plus thickness.

 

[r896neo]

Furthermore do you know exactly what PVA he used? there are different grades of pva and sbr looks very similar.

It does sound like he knows what he's on about but again personally i'd not lay such thin tiles on anything other than a concrete slab.

 

[mugginstoo]

Hello

Thank you guys for responding. Cannonfoder, you have said exactly what I thought from reading different internet sites. Yes the tiles are natural slate, so too late now to seal before laying. The tiles do not rock around as such as they have been tapped down into a wet sand and cement base of about 4", but he hasn't used one of the bonding agents you mentioned.
r896neo, thank you too. They are most definitely a tile not a flag. I think this is the first time he's laid this type of tile. I think the best method would have been a solid concrete base and tile adhesive as you two have both said much the same as I'd previously read. I did not ask the sales girls about laying because it didn't occur to me that the landscaper wouldn't know or check what was best for this product, especially as he didn't give me a specification. I did watch a video of a similar tile being laid and it was done with a deep mortar base, but they put a 1:1 sand cement slurry on the back of the tile and they were being placed within a boundary wall. Thank you for your comments on sealing that has put my mind at rest on that front. Well I'll have 50 teenagers partying on the patio this weekend before I've paid the final amounts as the whole job is not finished on time. If it survives that I suppose we found a new way to lay. I will also ask for a guarantee so should it all fall apart he has to return money or repair. I'm hoping the walls surrounding most of the patio will keep the tiles in place, nowhere to move to so to speak. The PVA says strong or high concentrate I think and has a large 1 from top to bottom of the carton.

 

[r896neo]

Well if it is definately PVA then its no use in this situation.

Sounds like poor management of the whole thing.

When he came to quote for the job what did you say you were sourcing? Slate flags or tiles?

If you want to save money by trying to source products yourself then you are responsible for those products being suitable and if needed checking on how the MFTR or supplier recommends laying them.

Of course he is laying them and so should tell you if his opinion is different to that of the supplier, but confusion and little difficulties are a common issue when people source their own flags etc

I don't think there is too much issue with the 100mm screed instead of concrete but really the screed should have gone in and let cure for a couple of weeks and then been tiled over with tile adhesive.

 

[mugginstoo]

Thank you.
I think I told the guy I was buying slate and did not specify flags or tiles. When I was originally looking I was searching for 20mm min. The original supplier ran out of stock and I could only find the rustic slate Brazilian rather than Chinese from this supplier. When the guy saw them he said they were thin, when he started laying he didn't follow my instructions which were from you tube to be fair to the landscaper. The supplier told me to follow the advice of my landscaper. After he had laid 4 tiles I said we can always stop, return and buy something you are more familiar with, to which he replied I'll work with these they'll just take longer to lay because I have to tap down very gently.

I'm just hoping the weather point holds it all together.

Thank you so much for your comments.

 

[r896neo]

Your supplier doesn't sound great if they won't even offer advice on how to lay them. They are the ones who guarantee the product and so their guarantee only applies if they are laid to a certain specification.

I would say the bedding technique is ok its just the possible adhesion problem. This isn't alway an issue but you'll soon know after a few hard frosts.

If the worst came to the worst at least the sub-base and the bedding could be re used and the whole lot re-layed over the top with tile cement.

Good luck with it and next time use a more reputable supplier or let the contractor supply the product.

 

[mugginstoo]

Thank you for your advice. The supplier of the tiles does offer advice and supply the necessary products to lay properly.
I should have been firmer at the beginning. When the landscape guy commented on how slim they were he only said tapping down would be slow because they wouldn't withstand a bashing. I never expected him to use pva as an aid to adhesion. He laid 4 tiles which were left as instructed untouched for 3 days. When I stepped on one I heard movement and could just pick up with my finger. I mentioned this and was told they would bed down once completely dry. I didn't want to insult the guy and felt he was the expert and would surely check his work before he went to far. It was at this point I offered to send these tiles back and get something he was familiar with laying.
Well at least 10 have lifted and that's without any frost.
I reckon give it a month or so of good use and they will all have come apart from the base. Looks like I'll be doing it myself. I'm not confident to lift without damaging the tiles so I think I'll wait, then I suppose its a tidy up of the base clearing any residual grout then a big fat deep bed of tile adhesive, or that thin set mortar I've read about and off we go again. Spirit level at hand.
Would I need to seal the sand and cement base before applying the adhesive?

 

[WabbitPoo]

For goodness sake - its clear now that they have not, and will not, stick down.....pointing is NOT a way of bonding the flags/tiles together.

They need to be taken up and remedial work undertaken. The contractor has failed so don't pay him.

 

[r896neo]

I agree with wabbit, this should be done by the guy you paid to do the job. If he is a reputable tradesman he will correct his work.

If you did re-lay over the screed with tile cement then follow the tile adhesive instructions for priming. A screed may not need primed depending on what mftr you use.

BAL make good tile adhesives.

 

[mugginstoo]

Thank you guys. The contractor hasn't turned up this week because he is waiting for the chap who is going to brake up the concrete road that runs down the side of my house before he can finish laying the patio and the new path that will replace the concrete road.

I am hoping he will see all the lifted tiles and realise himself and approach me, so I don't have to confront him. If not I will definitely not let him finish laying with his method.

Thank you for your comments on good adhesives I will check very carefully what is chosen for the relay.

I must sound like a fool but I did get recommendations from neighbours and 3 quotations. The job is over £5500.

 

[mugginstoo]

Hi again. The landscapers are back and have agreed to lift the tiles and relay using a modified thin set mortar, which they have now been told is the best product for external use. While looking for help I have read that this is a good adhesive and works well with natural slate tiles.
My question is where can I get it from? Looked at websites for major chain builders merchants and I've not found it. Plenty of suppliers in US Spain Italy but so far not found any suppliers near home.
r896neo, your advise to try BAL adhesives, do you know if this is similar? Sorry to keep asking for help, it's so reassuring when talking to these guys. There are lots of companies selling their own brand exterior tile adhesive but I've heard some are better than others. So advise from anyone with experience of laying 12mm natural slate externally would be very helpful.

 

[r896neo]

As long as you use a decent tile cement suitable for exterior use from one of the major players it will be fine.

BAL or Ardex

Something like BAL supercover rapid set should do the trick Or ctf4 if you dont want it rapid setting.

Make sure its a dry powder product mixed on site because the premixed stuff whilst fine for bathrooms etc Outdoors is a more critical environment so just take the tiny risk of getting old stock thats been sitting too long out of the equation.

Don't be confused by jargon, modified thinset mortar is basically just tile cement.

If your at all unsure ring BAL they have a good and helpful technical advise line and get it straight from te horses mouth.

 

[mugginstoo]

thank you. I got the BAL adhesive today. Was told £45 per bag retail? Did manage to get it down to £207 for 9 bags. Have I still paid too much?