tiling over Karndean floor?

Hi, if it's a conservatory then the Karndean will (should be anyway) stuck down with a flexy adhesive - mega strong and a nightmare to get up.
HSS in Preston hire a vibrating floor scraper which would shift them.

In theory you can tile onto Karndean.
Putting cables direct onto it though is asking for a world of pain.
I would either remove it, or quicker still, bond 6mm marmox boards to it, then ufh cables, screed and tile.

@gracesdad @GAZ_BAL_PST quality advice as always chaps.

Hardibacker will sap the heat and draw it down rather than reflect it up.
It's a cement/silica board, so it has poor insulation values.
Marmox / Warmup / Wedi will insulate it properly, and give you a nice surface to tile to.
(Wedi will be the best choice - CTD at Lytham if I were you!)

Heating direct onto the karndean will make the karndean soften and move.
That movement, although small, will pretty much certainly be enough to break the adhesive bond between the karndean and your tiles.

Tell your customer that the initial outlay for the insulation boards will soon pay back in terms of saving electricity.

Gaz made a good point too - strip the wax polish off the karndean before you stick anything to them. Most times they have some kind of polish on there. Either strip it with the proper strippers, or just sand it up rough.

Agreed and it'll go down a lot quicker!

Once polish, wax or grease are removed from the vinyl, you can fix boards using Rapid Set Flexible if that is your preference.
Gaz

tilerblackpool1 said:

Hi guys. Im anew on here and thought id get started with my first question to see what you guys think!

Basically, ive been tiling for 5 years and never come across this one.

I have a lady who has a conservatory which she wants undertile heating fitted and tiling. It has a solid concrete floor with Karndean Stuck to it (REALLY WELL!)

Question is.......can i tile and install undertile heating straight over the top of this karndean floor??

thanks in advance
Tilerblackpool

Well simple answer is no, you need to lift it as you don't know if the concrete is dry enough for the karndean Rh must be below 75% if it isn't the karndean WILL eventually blow and cause problems with the tile as the movement can be quite drastic, what adhesive was used as HT adhesive which is recommended for conservatories but wrong may react with the heating, if they've use pressure sensitive it will react with the heat.

GAZ_BAL_PST said:

Hi tarkett85,
How will the Karndean react to ufh heat when it has insulation board over it 1st ?
If damp was to effect the Karndean which has already been fixed down it would have after a very short period of time after initial install.

the moisture could have been absorbed into the concrete if the DPM has failed AFTER the karndean was fitted, according to the tech at karndean the insulation boards can let hot spots bleed through affecting the LVT in small areas which according to them is worse than the whole installation receiving equal heat. Just informing direct from karndeans mouth.

GAZ_BAL_PST said:

Thanks for the information, I never knew insulation boards bled heat through them with domestic cable systems. And of course, if a DPM fails then the damp will effect any type of flooring finish.
Gaz

i didn't know myself until i asked the question, learn something new everyday