Incorrect Adhesive Used - TilersForums.com

[Kemp8094]

Hello,

I have mistakenly used non-flexible Unibond rapid set floor and wall tile adhesive on my underfloor heating project downstairs in my living room.

I put down tile backer/insulation boards on a concrete base then I laid about 5mm of wickes self levelling compound that is suitable for underfloor heating. On top of this I then used the unibond stuff, which was wrong.

I am a little worried that it's going to go wrong and was wondering what the chances are of it mucking up?

I don't fancy doing it all again to be honest and the tiles seem to be stable so far although they have only been fitted for 4-5 days.

I have seen after googling that it can be real nightmare.

Thanks for any input

 

[Dan]

It wont expands so will presumably crumble a bit or crack and break at least.

What's done is done.

If you didn't use the heating it might be alright. It's just an average floor then. But it's when the heating heats up and cools down you'll get problems. It might not be the first time you use it but it will do something eventually.

 

[Kemp8094]

Oh right,

Well I will just use the heating an see how it goes. I only put underfloor heating in the parts you walk on so if it comes to it I will just have to fit them ones again.

a lesson learned for next time I guess.

 

[Old Mod]

Have u switched it on yet?
The longer u can leave it before u do, the better chance u'll have. U never know u might be lucky.
Are you aware of how to use the heating for the first time?

 

[Dan]

That might make it less of an issue but it might also make it worse because that area will expand and the other areas either side wont. So the weak point could be the connected area between the two.

Keep us in the loop.

 

[Kemp8094]

I have only turned it on to see if it heats up a bit, after about 2 - 3 days after checking the resistances and then it was only about 2-3 degrees above ambient temperature.

Going to Greece for a week on Saturday so it will be off the whole of the next 12 days.

 

[Old Mod]

This was after it was tiled, yes?

 

[Kemp8094]

This was after it was tiled, yes?

Yes, but I haven't grouted it yet as I realised I had used the wrong stuff.

 

[Old Mod]

The fact that it's not grouted is a plus, good call! I realise it's not ideal, but if I was gonna chance it like you've suggested, then I'd wait til you return then turn the heating on to its minimum then increase the temp by 2degrees a day to the maximum. Leave it full blast for 24 hrs and then reduce it in the same manner until it's off. Let it cool completely then turn it back on again. Then see what state the floors in.

 

[Old Mod]

......and then grout it!

 

[Kemp8094]

The fact that it's not grouted is a plus, good call! I realise it's not ideal, but if I was gonna chance it like you've suggested, then I'd wait til you return then turn the heating on to its minimum then increase the temp by 2degrees a day to the maximum. Leave it full blast for 24 hrs and then reduce it in the same manner until it's off. Let it cool completely then turn it back on again. Then see what state the floors in.

What is the maximum? The thermostat seems to go up really high? It's 150w kit and just wires, not matting. I haven't had it up really high just noticed that you seem to be able to keep upping the heat.

The grout I got is flexible it's from BAL.

 

[Dan]

.... with flexible grout!

 

[Dan]

What is the maximum? The thermostat seems to go up really high? It's 150w kit and just wires, not matting. I haven't had it up really high just noticed that you seem to be able to keep upping the heat.

It wont go past a certain point. Defined by your own floor there's no rule for it per se.

But just when it doesn't seem to go any warmer when you're doing the 2 degrees a day thing, stop and keep it at that temperature for 24 - 48 hours. Then slowly down a degree or two a day until it's always off.

Then use it as you wish.

I'd perhaps always tease it on and off so it's not a big shock going from cold to hot which is when it'll crack or whatever might happen.

 

[Old Mod]

Every ufh system is different, @Dan may be able to give u specifics on that.
Flexible grout is good. The Bal goes off quickly, do small areas at a time.
Dan is correct u probably will get issues but if you're gonna try leaving it then u need to give urself every chance.
You will soon tell if it's failing, the grout will crack first.

 

[Dan]

I'd suspect if they used AD1 in standard grout, it'd be super flexible and not crack, but the adhesive still might.

Best to always increase it only be a degree or so a day to running temperature in the colder months.

Never just whack it on full and go for a shower etc.