Is this prep ok...

[Spare Tool]

Hi all

Theres a lot of conflicting advice all over the web on this one so can anybody agree this will be ok?
Job is an 8sqm kitchen floor, 300x300 granite tile with ufh also tiles cut to form 150mm skirting tiles.
Substrate is asphalt on concrete.
My proposed prep...
Slurry coat on asphalt then 10mm webber fibreflex leveller
Insulation boards secured with flexi addy
UFH layed then covered with fibre leveller.
Then tile with flexy addy.
Does that sound ok?
Extra Questions
Is the slurry coat necessary on the asphalt or will just a good lick of SBR surfice?
Does it need or would benefit from uncoupling before tiling?
Any preference to thickness or type of insulation boards?
Is there a maximum wattage of UFH that should be used?
Will it need any expansion joints apart from siliconing around room where floor meets skirting tiles?

Advice appreciated

Andy

 

[Spare Tool]

No takers, how would you guys prep this, if I'm way off the mark please tell me, always willing to learn and take constructive advice....

 

[Rookery]

My method would be:
Fix 6mm insulation boards with Keraquick. Lay ufh cable and cover with Renovation Screed. Fix tiles with Keraquick. I wouldn't slurry coat or sbr, just make sure the asphalt is clean, dust free and dry. I wouldn't uncouple. 10mm insulation obviously better than 6mm but depends on height issues. I'd go for 150 watt psm. I would have a perimeter movement joint only with that size floor.

 

[Qwerty]

Slurry coat on asphalt then 10mm webber fibreflex leveller

Insulation boards secured with flexi addy

UFH layed then covered with fibre leveller.

Then tile with flexy addy.

Does that sound ok?


I assume you are referring to old black bitumen type adhesive? If this is the case, then yes to all the above steps but you may well not require the SLC in the first step. How uneven is the floor? If it is more then say 5mm then yes, but if not then I would just stick with the SLC at the UFH stage. See my note below re decoupling.




Extra Questions

Is the slurry coat necessary on the asphalt or will just a good lick of SBR surfice?

Yes, do slurry coat as the SBR won't provide any key at all


Does it need or would benefit from uncoupling before tiling?
Yes I would decouple above the SLC & UFH


Any preference to thickness or type of insulation boards?
10mm Marmox is my personal choice


Is there a maximum wattage of UFH that should be used?
In your circumstances 150w

Will it need any expansion joints apart from siliconing around room where floor meets skirting tiles?
No

 

[Spare Tool]

Yes its the old bitumen I guess around 20-30mm thick...its not a great deal off level and flat was thinking more on the lines of keeping any heat well away from the bitumen as could end up a disaster but I guess the 10mm marmox boards should do this, and uncoupling should belt n braces the job..
Will advise customer that's supplying no more than 150w ufh.
Great advice, that's what the sites for...
many thanks Andy

 

[Just Rizzle]

by using the insulationboards this is a form of decoupling as the boards are made of foam why do it twice

 

[Spare Tool]

by using the insulationboards this is a form of decoupling as the boards are made of foam why do it twice

If the job hadn't been on asphalt and just concrete I wouldn't even have posted this, just trying to make sure its done correctly...I can see your point Ray but insulation boards are insulation boards meant for retaining and forcing the heat upwards, and an uncoupling membraine is just that, like I said its belt and bracing the job but for an extra £100 to ensure a long lasting no fail job cost wise I think its worth it, if I were the customer and someone gave me the "well it might be ok or it will definitely last a lifetime for £100 bats" I know which one I'd choose

 

[Qwerty]

by using the insulationboards this is a form of decoupling as the boards are made of foam why do it twice

Insulation boards are not a suitable substitute for a decoupling membrane, therefor it would not be doing it twice

 

[Dave]

Ray is correct , although not a 2 part separation like Ditra , extruded foam boards do in theory uncouple the tiling field from the substrate when not screwed in-situ.

I personally wouldn't use both boards and matting.

 

[Qwerty]

Ray is correct , although not a 2 part separation like Ditra , extruded foam boards do in theory uncouple the tiling field from the substrate when not screwed in-situ.

I personally wouldn't use both boards and matting.

I agree Dave, "in theory" they do, but they are not guaranteed to decouple and I would be very interested to know of a company who do as I could start saving myself (customers!) a fortune!

 

[Dave]

Certain scenarios like this floor Geoff , then I would just go the boards ... BUT I deffo agree that when a floor to be uncoupled , then the membrane is the way and I know ray would also use matting , just this particular job I wouldnt .. Hence imo ray wasn't incorrect , thats all I meant

 

[Spare Tool]

Jeez at the beginning of my post I did say there's a lot of conflicting advice on the web on this one and so it continues...but I guess we all do things slightly differently, long as the job's done properly and made to last that's the main thing...
Made my mind up and will go with the 10mm insulation boards and uncouple over last layer of slc just before tiling.
I did ask if it would 'need' or 'benefit' from uncoupling and I'm guessing the answer to that is 'benefit'. All good advice as ever.
Thankyou for all your input guys