Correct Tile Adhesive

[Alan McNally]

Good morning,

I am looking to tile my kitchen floor. The floor is 22mm tounge and groove overboarded with 12mm external ply screwed at 100mm intervals.

I have been doing some research into the best adhesive for the job and the Mapei brand seems to get good reviews (I am also considering BAL). I just wondered if anybody could advise me on which Mapei product to use (the tiles are granite). I have tried asking their customer support but have had no reply.

Also do I need to install a decoupling mat? I understand it is meant to help with lateral movement but can't see why the floor would move.

Any advice would be appreciated,

Thanks for your help,

Alan.

 

[Flintstone]

Hello, I would go for there s2 rated adhesive. I beleive it's called s2 ultra flex. Decoupler would add some extra security for you as wood can expand and contract and with granite being Leeds stable than porcelain.

 

[Flintstone]

Tilemaster ultimate would be my adhesive preference, if there is a stockist near by.

 

[Alan McNally]

Hi, thanks for the reply. I'll look into the tile master adhesive you have suggested.

Any particular reason why you would choose it over the mapei or is it just personal prefrence?

With regards to the decoupling mat, would you stick with the same brand as the adhesive or is it ok to mix and match?

Kind Regards,

Alan.

 

[Andy Allen]

I would put hardie down first....hate tiling on ply with a passion...

 

[Alan McNally]

Hi Andy,

I wish I had used a backer board now but I've already laid the ply, didn't realize the product existed till it was too late. Would you lift all the ply and replace it?

Looking at the price of that anti fracture matting I'd probably still be cheaper doing that instead of buying the matting to put over the ply!

Thanks.

 

[andy8758]

I don't believe decoupling membrane is necessary, but the S2 grade flexible adhesive is advisable as a "belt and braces" (avoid de bonding or cracking tiles) option. The ply should have a coat of SBR bonding primer applied to rear face and edges of ply (helps prevent drying too rapidly, and thereby the tile adhesive bonds better to the wood). However the S2 adhesives can be expensive (retail prices from £40 to £90/ 20kg bag - you will probably need between 6 and 8 bags). If you are in a building trade you may benefit from opening a general traders account to get additional discount on prices.

I agree with Andy Allen, ply is not the best surface to tile into, but if you follow the adhesive manufacturers advice, you should not get any problems.

 

[Alan McNally]

Thanks for the input Andy. I've checked out the adhesive options mentioned by localtiler and the Tilemaster S2 adhesive is coming in a good bit cheaper than the mapei so will go for it.

Unfortunately I didn't prime the back of the ply before fixing it down. Would you recommend I lift it to do this (or do I risk delaminating the board?). I understand what you are saying that the adhesive might dry out too quickly so if it needs to be done I'll do it, at the end of the day I don't want to regret it later down the line.

Thanks again.

 

[Flintstone]

I would not lift the ply to prime the back of it, it's good quality ply you have put down by the sounds of it so I don't think you should have any bother. One thing I forgot to ask, is the tongue and groove fixed down? It's not a floating floor is it, over a solid floor?

 

[Alan McNally]

Ok thats good to know. I bought the ply from the local builders merchants so can only hope it is of a reasonable quality, it is definitely external grade. The tongue and groove is fixed to the floor joists,I made sure to put extra fixings into any suspect boards before overbearing with ply then when screwing the ply down I used long screws where it crosses the joists so hopefully it is as solid as it can be.

So just to summarise from all the advice so far...

I'll go with the tilemaster ultimate s2 adhesive and apply directly onto the bare ply with no decoupler. I intend to go with a 10mm notched trowel and back butter the tiles. I have also bought the raimondi tile levelling system to give it a try.

Cheers to all who have helped,

Alan.

 

[Alan McNally]

Something else I forgot to ask...

The tiles are 600x300 what would be the standard spacing between tiles? I have read that 3mm is the minimum?

Also any recommendations for a decent quality grout?

Thanks again.

 

[Rookery]

Priming the back and edges of the ply is to prevent moisture ingress, not to prevent the adhesive drying too quickly. In any event, BS calls for a ply overlay to be minimum 15mm thick and of WBP or Marine grade, so your overlay is already under spec and possibly not the best quality. I would take it up, overboard with Hardie glued and screwed and fix tiles with Mapei Keraquick using 3mm spacers, grouting with Mapei UCP. Alternatively I would fix with BAL Rapidset Flex. I've never used Tilemaster but it gets good reviews. I might use an uncoupler too depending on the size of the floor and how stable I felt it to be.

 

[Alan McNally]

Hi,

Thanks for your advice. I have been thinking about what you say regarding water ingress to the ply, surely if there was moisture present enough to cause an issue with the ply then even if it was primed on the back egde I would still have a problem, after all if the ply is securely fixed to the tounge and groove so if moisture was present would the tounge and groove not react to it and take the ply with it causing shrinkage/expansion anyway?

I have read through the prep guide for the tile master s2 adhesive and they say 12mm ply is fine for overboarding the existing floor?

Like I said previously if I need to replace the ply then I will do it. Appreciate all the advice but there seems to be quite a difference of opinion with how best to proceed.

Thanks,

Alan.

 

[Andy Allen]

Main issue you get when tiling a wooden floor is deflection.......it has to be as solid as you can get it with no bounce.
I've seen many failed floors that have been tiled on ply or chipboard mainly a combination of to much bounce and the adhesive not sticking to the wood for one reason or another.
You could just overboard the ply with 4 or 6mm cement boards if extra hight isn't an issue.....this would be belt and braces approach...
If I had to tile on ply I would use bal single part fast flex and bal wide joint grout with GT1 admix.
And use the adhesive as per instructions and back skim the tile .

 

[Alan McNally]

Hi Andy,

Thanks for the reply...

I have checked out the BAL adhesive you mentioned, I wasn't ready for the £45 per 12.5kg price tag haha! I know you get what you pay for but

I can get the tile master ultimate s2 for a good price, have you had any experience with it? If I really need to go with the cement backer boards I think I'll just lift the ply and replace it to keep the height difference between rooms to a minimum.

One thing I didn't mention before was the when I gutted the room for renovation I removed tiles from the same floor. The ply that was down was only thin (3mm I'd say) and just nailed to the tounge and groove, tiles appeared to be porcelain but I don't recall seeing any cracked tiles or grout so hopefully that puts me in a good position.

Cheers,

Alan.

 

[Alan McNally]

Ok, I've decided to lift the ply and replace with a backer board. Just a quick question, I was looking at the 6mm marmox board. There are a lot of posts advising the boards to be fixed to the sub floor using both adhesive and screws but the marmox instructions say adhesive OR screws so I was just going to screw it down. Is this ok?

Thanks.

 

[Andy Allen]

The adhesive will fill any voids and make a much better job..

 

[Alan McNally]

Ok Andy thanks. Can you please recommend the correct adhesive for bonding the backer boards to the tounge and groove and also would I still use an S2 type adhesive for bonding the tiles or would this be overkill?

Thanks again.

 

[Andy Allen]

Any cement based adhesive to stick down the boards it doesn't have to be expensive as it's just to fill in the voids just make sure you screw them down as well.
And yes I would still use an S2 type of adhesive to tile.

 

[Alan McNally]

Ok Andy, thanks again.