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

[raylincs]

Hi Everyone
Looking for some advise.
I have just been to look at a job that has, Karndean flooring on a concrete floor substrate, and has electric underfloor heating.
1. Would you take up the Karndean floor (in V good nick)
2. If not taking up the Karndean, what adhesive would you use?

Many thanks
Raylincs

 

[cam_low]

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

Karndean up, remove as much glue as physically possible, prime with SBR, self level, or not, then tile.

 

[raylincs]

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

Karndean up, remove as much glue as physically possible, prime with SBR, self level, or not, then tile.

Hi Cam_low
Thanks for replying, the area is 40sqm and the Karndean has been put down with special adhesive for underfloor heating. I was wondering if i could rough-up the surface of the Karndean, then prime with SBR and tile with flexible adhesive.
Thx

 

[Rookery]

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

I've tiled straight onto Karndean with 600 x 600 porcelain using BAL tile and stone PTB. As long as the Karndean really is well fixed, give it a good clean, rinse, dry and tile away.

 

[nybor62]

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

take up karndean imo, what tiles are u fixing

 

[ythan]

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

are you sure it's electric underfloor heating within the concrete floor substrate? sounds unusual but maybe there's insulation under the concrete to prevent large heat loss.

if it is electric then maybe a few problems:

- the electric matt/cable will have been laid in a relatively thin screed on top of the concrete slab- removal of the karndean may result in damage to screed and the electric matt/cable. the karndean can be pretty difficult to remove.

- is it possible the karndean will overheat when covered by tiling - probably not.

don't think there's any problem with tile tiles sticking to the karndean - to be safe use Bal single part Fastflex, which is lower cost and much easier to use than the 2 part fastflex.

suggest you could do a trial fixing of say a square meter of tiling to check for any problems - it is a large floor area.

 

[peteablard]

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

Take it up, why risk it? If a jobs worth doing.........

 

[raylincs]

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

Thanks to everyone who has replied. Just to clarify I have found out; the electric underfloor heating is a thick cable laid into a weak sharp-sand and cement substrate (insulation under this) with a thin self-levelling compound on top. The Karndean has been put on with Karndean's own underfloor heating adhesive.
The area to tile is 40sqm with Porcelain 390 x 590 x 10mm tiles.
It sounds as though the replies are split between taking the Karndean up and leaving it down.......
I appreciate the replies

 

[ythan]

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

Risk = (probability of something happening) times (the consequence of it happening).


Why it worrh taking a risk? - to win benefit for the risk taker.



Solution:
Share understanding of the risk with the customer, get the job, and share the benefit with the customer.

How much would it cost to take all the Karndean up, level etc? And what's the risk of damage to the electric underfloor heating?

I'd go with tiling over the karndean with Bal single part fastflex.

Talk to your customer.

 

[Ajax123]

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

Thanks to everyone who has replied. Just to clarify I have found out; the electric underfloor heating is a thick cable laid into a weak sharp-sand and cement substrate (insulation under this) with a thin self-levelling compound on top. The Karndean has been put on with Karndean's own underfloor heating adhesive.
The area to tile is 40sqm with Porcelain 390 x 590 x 10mm tiles.
It sounds as though the replies are split between taking the Karndean up and leaving it down.......
I appreciate the replies

That has failure written all over it.

Also the adhesive will have a temperature condition on it. From memory i thinkthe karndean adhesive is such It should not exceed 35degrees c (or might be a lower spec a 29degree adhesive). This is important because as you are tiling you will significantly increase the temperature at the gue line as your tile will move the temperature thresholds within the floor strata upwards. This could easily increase the temperature at the karndean glue line above its safe threshold causing it to soften and delaminate.

i am firmly with the "take the karndean up and remove as much glue as possible then self level and tile" crowd

 

[ythan]

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???

 

[raylincs]

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

 

[peteablard]

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

If the customer wants it taken up then why are you asking about leaving it down?

 

[raylincs]

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

Sorry missed the word Not, out..
The customer of course is hoping for the Karndean NOT to be taken up, and all the problems and costs this would entail

 

[ythan]

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

if cost to the customer is no problem, then it's all down your own professional responsibility.

and if your customer is pleased & can put your way other customers, that also do not consider cost, then you've have even more professional responsibility and plenty of work.

beware damaging the electric underfloor heating.....

talk to your customer and get him/her to agree to what you recommend doing.

 

[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.

 

[peteablard]

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

single part fastflex

Single part fastflex

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

some manufacturers also tell you to use PVA, I personally don't trust everything they say. If I'm guaranteeing it then it's done my way......