Tiling concrete floor and UF heating

[The Tiler]

Steve, the reason I stopped using these boards is because the need to prime face and underside. Yes the boards are cheep, but the time and space needed to prime and then completely dry let them dry is uneconomical.
The unprimed boards have added to the failure and not fixing to a flat surface, SLC, was the first mistake.
How you proceed now is between you and your old / new tiler.
I would be very surprised if a new tiler is happy to continue the work knowing the problems.

 

[Flintstone]

Steve, the reason I stopped using these boards is because the need to prime face and underside. Yes the boards are cheep, but the time and space needed to prime and then completely dry let them dry is uneconomical.
The unprimed boards have added to the failure and not fixing to a flat surface, SLC, was the first mistake.
How you proceed now is between you and your old / new tiler.
I would be very surprised if a new tiler is happy to continue the work knowing the problems.

Hello Mr tiler, introduce your self !

I'm not sure which boards you are referring to but none of them need priming, coated or not. I personally prime the face to be tiled once the boards are down but it's not really required

 

[The Tiler]

hi Local
the XP pro type, insulation foam only, comes in blue or cheaper yellow from my supplier. Use only the backer board / fibre glass cover insulation now.
It no longer says to prime the underside on the fixing info but always did and logic says it needs doing. If top side needs priming before applying SLC or adhesive why would the underside not need it?

 

[Flintstone]

The blue or yellow uncoated boards shouldnt be primed. The coated boards I only prime the surface to stop it sucking the moisture from the slc quickly and to help it flow, there's no point priming the back at all

 

[The Tiler]

sorry Local, don't want to come on here and point out you maybe wrong
just checked again and here is a screen shot

item 3

 

[The Tiler]

don't know what happened there,
yesterdays walk on the beach pic

 

[Flintstone]

That is referring to boards to take pipes for water underfloor heating

 

[The Tiler]

it is, but is exactly the same material. Did have the same product info for the ungroved boards upto recently.
Why would you treat the same material any different? Both are stuck down to the sub floor with the same tile adhesive.
It makes no difference what the heating is on top, wire or water, or board thickness imho.
we are all here to learn, and I am happy to be shown I doing something wrong.
be interesting to here if any other Trusted Advisors have used these products and there fixing methods.
I use the water pipe ones a fair bit with a local plumper doing the wet bits ready for me to tile using Ditra or 10mm SLC ready for others to put on other floor covering

 

[Flintstone]

I agree it doesn't matter what's on top it is the same material If they are the foam type. There is a few types of carriers for pipes that's why I asked. I only ever use coated board as they are far superior

 

[The Tiler]

haven't found a coated board to carry wet ufh pipes yet, have you a link for one please.
as I said I change, as you, to coated one for electric ufh wires

 

[Waluigi]

Why is wet UFH being mentioned. This thread is about electric UFH. It says so in the first post

 

[Flintstone]

Foil coated, gypsum based boards are available for wet underfloor heating. You can argue with me until you are blue in the face, you do not need to prime the back of bare foam boards or the cement coated ones. Regardless of what ultra say on that bumf you have posted ! Priming the face of cement coated is best practice for SLC.

 

[hmtiling]

we're getting off topic here but the uncoated xps are terrible. just looked at ufhs installation guide and video and it doesn't metion priming the boards. I'm aware the wet ufh carrier boards should be primed though, so it won't hurt obviously.

 

[Steve01]

Steve, the reason I stopped using these boards is because the need to prime face and underside. Yes the boards are cheep, but the time and space needed to prime and then completely dry let them dry is uneconomical.
The unprimed boards have added to the failure and not fixing to a flat surface, SLC, was the first mistake.
How you proceed now is between you and your old / new tiler.
I would be very surprised if a new tiler is happy to continue the work knowing the problems.

Thanks @The Tiler

I did pull a bit of the floor up today where there is no underfloor heating to see what is happening - and as you say the underside of the XPS has not stuck to the adhesive but the adhesive is firmly stuck to the concrete floor

Priming the underside of the board would have solved it and not something anyone initially recommended including the board manufacturer so don’t feel so bad now and actually can’t really blame the tiler

1000s of these are sold and I wander how many people have had the same problem without knowing

The only reason I have noted it is that I asked the tiler to let it dry properly and also have been walking on the kitchen floor with socks over the last few days so I can feel everything with my feet

If it had dried the next day with warmer weather and tiler had tiled straight Over I probably wouldn’t have noted anything

I will consult with the new tiler but believe I have 3 options

The 35sqm floor is 90% sound with about 8 patches of about 15cm diameter where there is some slight movement

1. Rip up entire floor and start again - sounds drastic and probably not needed - regret cost probably £1000
2. Ask new tiler to remove in small sections the areas with the movement and then prime and apply flex adhesive when tiling - willneed to be done carefully to avoid damage to UFH
3. Do nothing and just tile - tiles are 60cm x 60cm so with the small 15cm radius patches with air it’s going to be almost impossible that any direct pressure will ever go on these patches as pressure will be spread across the tile and even when I press on them directly now with the heel of my foot movement is so small and it doesn’t seem to do any harm to the surface - I guess that’s the benefit of the flexible compounds

Anyway I know it’s hard for people on here to give opinions as some of the members are unforgiving but happy to hear

I think I may be overthinking this and being paranoid but one of the key lessons as the tiler says is to use tile backer board and not these cheap XPs boards

 

[Flintstone]

Double post

 

[Flintstone]

The key lesson here steve is to do the job properly from the ground up with a reputable tiler who knows what he's on about. The uncoated boards are not the cause of the problem neither is the fact they were not primed. Yes they are inferior but they are still suitable if used correctly

 

[Bathfix Bob]

If nothing else please say they are porcelain tiles?

 

[The Tiler]

thanks Steve
the floor prep wasn't right, needed SLC
imho the second error was not priming the boards underside.

a new tiler should not continue with this install as what he is tiling onto is not sound.
the areas of failure are small, may get bigger, time will tell.
I would be surprised if tiling over these areas doesn't give you an a floor you are happy with but that something between you and your fixer to talk about.

 

[The Tiler]

Foil coated, gypsum based boards are available for wet underfloor heating. You can argue with me until you are blue in the face, you do not need to prime the back of bare foam boards or the cement coated ones. Regardless of what ultra say on that bumf you have posted ! Priming the face of cement coated is best practice for SLC.

I'm not here to go blue in the face! I'm asking questions and passing on my knowledge which I believe to be correct unless I'm shown to be wrong, may will happen
as for foil covered gypsum boards I wouldn't touch for any reason. Is there a thread you can point me to on how to fix to these please.

 

[Spare Tool]

Ive fixed those un-coated boards a few times and never primed either side of em yet..just stick them with a wetter mix of adhesive making sure not to trap any air pockets under them. The problems here have come from trying to stick them to a floor that wasn't leveled over in the first place..

 

[The Tiler]

hi Andy
not looking for argument on the subject and maybe getting of topic as harry said, but why prime top and not bottom? Both are stuck with adhesive

 

[hmtiling]

hi Andy
not looking for argument on the subject and maybe getting of topic as harry said, but why prime top and not bottom? Both are stuck with adhesive

I wouldn't use them again but priming the top would help the ufh adhere properly and prevent any curling and also aid flow of levelling compound

 

[Dumbo]

I haven't found a background yet that priming is detrimental . No need to prime and do not under any circumstances prime are two different things. But i havent used those cheap uncoated boards

 

[The Tiler]

looks like I'm out number but will still prime both sides as I believe it should be, have seen how bad a S1 adhesive sticks to an unprimed surface and sadly not found another product I'm happy using for wet heat. As for electric I'd use a covered backer board.
looking forward to reading other posts and giving input if I think it will be of assistance, please be gentle with the newbe

 

[Andy Allen]

I haven't found a background yet that priming is detrimental . No need to prime and do not under any circumstances prime are two different things. But i havent used those cheap uncoated boards

Depends on the adhesive being used.
Some state do NOT prime cement boards or light weight backer boards...

 

[Dumbo]

Depends on the adhesive being used.
Some state do NOT prime cement boards or light weight backer boards...

I've had that before . One which springs to mind was bal saying that about ply ( not that I was tiling to ply ) but it was in a similar conversation to this . So rang them up and challenged them over it ( I particularly like challenging bal self proclaimed messiah's of tiling ) and their response was you can prime it if you want to without affecting performance .

 

[Steve01]

If nothing else please say they are porcelain tiles?

Yes polished porcelain - what difference does that make ?

 

[Andy Allen]

I've had that before . One which springs to mind was bal saying that about ply ( not that I was tiling to ply ) but it was in a similar conversation to this . So rang them up and challenged them over it ( I particularly like challenging bal self proclaimed messiah's of tiling ) and their response was you can prime it if you want to without affecting performance .

This is taken from there pdf, the adhesive is bal single part fast flex, an adhesive I use all the time on wooden substrates with cement boards...

 

[Dumbo]

Right if you look at next paragraph down that is what I challenged them on. Saying do not prime surfaces to be tiled on . I challenged them and they ok not a problem . So I wouldn't rely on that . I've not finished bal tech will get a call from Mr pain in the arse from salisbury

 

[Andy Allen]

Right if you look at next paragraph down that is what I challenged them on. Saying do not prime surfaces to be tiled on . I challenged them and they ok not a problem . So I wouldn't rely on that . I've not finished bal tech will get a call from Mr pain in the arse from salisbury

I know first hand priming certain surfaces using that adhesive reduces the bond strength considerably.

 

[Dumbo]

This is taken from there pdf, the adhesive is bal single part fast flex, an adhesive I use all the time on wooden substrates with cement boards...

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So just had a chat with bal tech and they say no need to from their point of view but you could to slow the porosity of the board but you should check with the manufacturer . The guy was very non committal and ambiguous but at no point did he say do not do it . I also asked if it would be detrimental to the bond strength and he said no . I dont know if bal board is a lightweight board , i know it not cementitous but they recomend priming with apd