Tiling concrete floor and UF heating - Tile Advice

[Dumbo]

Harry said prime

 

[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