Tilling on a floor with Karndean already on floor & underfloor heating

[Ajax123]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

Ajax - are you also going to take up the ''weak'' screed and the electric underfloor heating?

who is going to pay for all this???

I am not going to be taking any of it up at all.

If I were i would know that it would not be necessary to take up the weak screed or the heating cables. If necessary this can be repaired using a stabilising epoxy. However you should also ask yourself who is going to pay for it if it fails.

It is worth thinking about the fact that karndean is relatively flexible and elastic so will cope better with the rigours of a mobile screed. If it is weak then it will be more mobile than a correctly made and laid screed. A rigid tile face may not cope as well.

I just think this has problem stamped in big bold letters on it based on the info so far.

 

[Ajax123]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

Hi everyone again thanks for taking the time to answer my post.
The underfloor heating never goes above 25c so that shouldn't impact the glue line (glue is Karndean's own for underfloor heating, so I will check their temperature threshold), also the tiles should disperse any temperature build up, I would have thought.
The customer of course is hoping for the Karndean to be taken up, and all the problems and costs this would entail.
I take pride in my work and rely on repeat business, so in a fix about this job.
Thx

Does the room ever get warm?? The 25degrees will presumably be the surface temperature based on the room temperature of about 20degrees. As it is electric it will presumably have a floor stat which measures the surface temperature. If you overlay all this with a tile you WILL increase the core temperature of the screed. If you are certain of your facts about the temperature then fine but I would need a little more info personally.

If you take pride then don't take risks. Do it properly.

 

[ythan]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

I am not going to be taking any of it up at all.

If I were i would know that it would not be necessary to take up the weak screed or the heating cables. If necessary this can be repaired using a stabilising epoxy. However you should also ask yourself who is going to pay for it if it fails.

It is worth thinking about the fact that karndean is relatively flexible and elastic so will cope better with the rigours of a mobile screed. If it is weak then it will be more mobile than a correctly made and laid screed. A rigid tile face may not cope as well.

I just think this has problem stamped in big bold letters on it based on the info so far.

Yes, OK, Ajax there's risk/cost all around - hence the need to discuss it professionally with the customer and agree what's to be done.

sounds like you would be willing to take all the risk yourself of not damaging the screed and the under-floor heating when removing all the karndean etc.

what % of cost do you think removal of the karndean would be?

 

[Ajax123]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

It depends really on how difficult it is to remove. A hot air blower would make it significantly easier. You can hire a striping machine but I don't have any experience of ths personally.

Just a question... How do you know it to be a weak screed??

 

[raylincs]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

Hi Ajax123
The customer has told me that the new extension which is two thirds of the tiling job, was a nearly dry sharp sand and cerment weak mix, laid on the electric cable underfloor heating, to a depth of 70mm. The a self leveling screed laid on top of that.
1/2 of this job is a kitchen with an island units, display units. A utility room and a sun room.
I think taking up the Karndean will take days even with a heat gun as the adhesive is heat resistance for underfloor heating.
Thx

 

[Andy Allen]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

sounds like a nightmare to me ,and one i would proberly pass on....

 

[ythan]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

so the heating cables are buried 70mm? - blimey, must take a long time for the floor to heat up, must be on all the time in winter.



still that means that the heat should be well distributed within the floor and there should be no local hot spots. also means should be little risk of damage to the cables should you decide to remove the karndean.




but I'd keep the job simple i.e. thoroughly clean the karndean, then use BAL single part fastflex. key thing is to follow the mixing instructions, and get a good even bed of adhesive.




I'm sure the job will be a good'un.




I'm assuming the other 1/3rd of the room is similar substrate to the newer 2/3rds part.

 

[Ajax123]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

Hi Ajax123
The customer has told me that the new extension which is two thirds of the tiling job, was a nearly dry sharp sand and cerment weak mix, laid on the electric cable underfloor heating, to a depth of 70mm. The a self leveling screed laid on top of that.
1/2 of this job is a kitchen with an island units, display units. A utility room and a sun room.
I think taking up the Karndean will take days even with a heat gun as the adhesive is heat resistance for underfloor heating.
Thx

forgive me if I'm reading this wrong but you seem to be seeking blessing to tile in a way that it should not be done on a substrate that is potentially poor. I have said the reasons why i Believe the risks to be present. I think you should take up the karndean, repair the screed as appropriate and then tile. Karndean is not considered a suitable substrate for tiling by an national or international standards that. Am aware of. Cold as it may seem I am completely un sympathetic to the thoughts or wants of the client or the time it will take to do the job. The cost is irrelevant. In order to do it correctly it costs what it costs and takes as long as it takes. If the client cannot afford to do it properly you have to decide if the risk outweighs the benefit. In my opinion based purely on what you have said it does. Regardless of any conversations or "agreements" you reach if it fails the client is likely to come after you as the tiler. You as thetiler having failed to meet the minimum requirements of the appropriate standards would be considered in law to be liable.

The fact it is electric cable underfloor heating is not relevent. It will be either a 6mm or 10mm Devi type system which is perfectly suitable subject to the temperature being controlled by floor stats rather than room stats.

It really is up to you though.

 

[DHTiling]

Alan , give up it is a lost cause. Some seem to know better.

We shall await the failure.


Sent from my iPhone using Tapatalk

 

[ythan]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

please all the tilers who are totally convinced that tiling over karndean is a total no go - can any of you describe, in a bit of detail, the failure modes that you're predicting?



a forum should be a place for discussion. don't just go off in a huff.

 

[peteablard]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

No one is going off in a huff, someone has asked for opinions and they have been Given. Nearly everyone has said it should come up, which to do the job correctly it should. There is only so long people will bang their head against a brick wall before they give up.......

 

[Gazzer]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

I really think you need to contact adhesive manufacturers , If one say that you can do it then "knock your self out."

 

[Rookery]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

I really think you need to contact adhesive manufacturers , If one say that you can do it then "knock your self out."

Thats what I did when faced with this situation a year or two ago. I spoke to BAL TAS and they said that providing the karndean was well fixed and I cleaned it well, it was ok to tile onto with BAL PTB Flex. So I did.

 

[ythan]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

[h=2]single part fastflex[/h]

[h=3]Single part fastflex[/h] USE FOR:-
Most types of FLOOR tiles including:

• Ceramics
• Porcelain and fully vitrified tiles
• Mosaics
• Natural Stone including marble
• Slate

Most substrates including:

• Asphalt (suitable grade e.g. flooring)
• Concrete, cement:sand screeds and rendering
• Existing vinyl tiles, unglazed ceramic tiles, quarry tiles, terrazzo and natural stone
• Fibre reinforced cement boards and lightweight tile backer boards
• Tongued and grooved floorboards
• Underfloor heating

 

[DHTiling]

Re: Tilling on a floor with Karndean already on floor & underfloor hea

Bal say it is good to go then go for it.... BUT when it fails , then see what response you get from Bal..

I shall not input anymore as cannot really add to the majority and cannot be assed to argue why with those that say it should be done... so as said above .. knock yourself out and don't complain when it does go **** up.