Underfloor heating between joists

[Simon Dale]

Hi all
Just looked at a job where builder wants to put down 22m chipboard over joists then Ditra. I said nooooo. The heating system is wet on a polystyrene board with aluminium trays screwed to joists. I have mentioned giffa flooring. The joists are 400 centres so could probably use the 18mm. Any advice on this would be helpful as the builder will do whats best for a change. 🙄🙄

 

[Waluigi]

Sounds like a job for Hardibacker, No more ply, Pro Ply or that Dukkaboard XL

I know for a fact that Pro ply is designed to go above UFH systems as I’ve read the technical data sheet. Not entirely sure on the others although it’s widely known that HB is OK above UFH.

Would have to be a thicker board though which limits some choices

 

[Simon Dale]

Sounds like a job for Hardibacker, No more ply, Pro Ply or that Dukkaboard XL

I know for a fact that Pro ply is designed to go above UFH systems as I’ve read the technical data sheet. Not entirely sure on the others although it’s widely known that HB is OK above UFH.

Would have to be a thicker board though which limits some choices

Im not in Hardie good books at the moment 😀😀😀

 

[Tile Shop]

Im not in Hardie good books at the moment 😀😀😀

Intrigued ..... what did you do?

 

[Waluigi]

Probably said it’s carcinogenic in front of 100 people all wearing those damn Hardibacker hoodies.

 

[Blunt Tool]

Im not in Hardie good books at the moment 😀😀😀

What did you do Laurel?

 

[Tile Shop]

Probably said it’s carcinogenic in front of 100 people all wearing those damn Hardibacker hoodies.

Ahhh.... that would explain it. Comments like that usually go down like a fart in a lift.

 

[Simon Dale]

Intrigued ..... what did you do?

Posted someone else floor . It was 18mm ply ditra and 1800x900 6mm tile. Its been down for 2 years with wet underfloor between joists not a crack in sight solid as a rock. I said basically who needs Hardie 😀😀

 

[Simon Dale]

Posted on TT its kicking off again 😀 Seems everything I post on there gets people angry 😵

 

[Waluigi]

Not that angry if you’re still on there 😉

 

[Simon Dale]

Not that angry if you’re still on there 😉

I just rant occasionally. Spoke with Bal technical not much joy even with Giffa floor

 

[Waluigi]

I’d look into NMP

 

[Simon Dale]

I’d look into NMP

I would like to use minimum 18mm ?

 

[Simon Dale]

Just looked they do 22mm 🙂

 

[Waluigi]

Yes, 3_fall swears by it.

You might swear when you see the price.

 

[Simon Dale]

Yes, 3_fall swears by it.

You might swear when you see the price.

Just looked 33 😱😱

 

[Simon Dale]

And its 65mts 😀
😀

 

[Waluigi]

Might be worth checking to see if it’s definitely suitable for UFH.......beneath.

 

[Simon Dale]

Might be worth checking to see if it’s definitely suitable for UFH.......beneath.

Will do but I think the Giffa is the way forward. Im not paying so cost is no prob 😵😵

 

[Waluigi]

Knauf Brio is another one to look at. Again, that is definitely suitable above UFH systems

 

[Simon Dale]

Knauf Brio is another one to look at. Again, that is defiejoy suitable above UFH systems

Seen it 🙂 Just wish there were no underfloor heating systems that are considered not safe practice for us tilers 🙁🙁

 

[Chalker]

I always bleat on about this, but just use Femacell flooring. Gives great conductivity for the underfloor and can be tiled straight onto.
I’ve done this numerous times, with no failures.
Ditch the ply

 

[Simon Dale]

Just an update. Builder spoke with Knauf today. He can use 18mm Giffa, not screwed into joists as it is floating. All I have to do is prime with their product no anti fracture and tile ???? I will do it 😱😱

 

[Blunt Tool]

what’s your friends on TT saying about that then?

 

[Blunt Tool]

Is it thin porcelain, normal porcelain or stone? Use Tilemaster anti fracture mat no matter what, it’s thin and for hundreds could save thousands.
Not too sure about no fixings into joists tho

 

[Dumbo]

Just an update. Builder spoke with Knauf today. He can use 18mm Giffa, not screwed into joists as it is floating. All I have to do is prime with their product no anti fracture and tile ???? I will do it 😱😱

Fix it to the joists . Stuff floating as it will and it will rock

 

[Simon Dale]

what’s your friends on TT saying about that then?

Not putting it on there 😱😱😱

 

[Simon Dale]

Is it thin porcelain, normal porcelain or stone? Use Tilemaster anti fracture mat no matter what, it’s thin and for hundreds could save thousands.
Not too sure about no fixings into joists tho

Its planks, Ive emailed Knauf see what comes back

 

[Simon Dale]

Heres the reply ?
Good Morning Simon,


Thank you for sending us the photo- so for the GIFA floor system it is a floating system and doesn’t need to be screwed into the joists. Knauf flooring edge strips are to be used on the perimeter of the system to absorb any movement and stop the transfer of sound through walls if the floor does move/buckle. A anti fracture mat would substantially help, other than that this is all we advise for the GIFA floor.


Thank you for your enquiry,


Please do not hesitate to contact us should you need any further information.

Kind Regards

Sam Bunting

Technical Support Trainee

Tel. (+44) 08000 304 135

www.knauf.co.uk

Follow us on twitter @KnaufTechnical

 

[Dumbo]

Anti fracture to help with a buckling floor . It just shows these guys dont know what they are on about and just make it up as the go along

 

[Dumbo]

I just noticed its from a trainee