Tiling concrete floor and UF heating

[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.