Electric UFH What SLC to use over UFL

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Kevin09

Hi All,

I'm finishing an extension off next week by installing a UFL heating system,I've done a few before but not for a while.
I'm happy with everything,but I'd just like to ask peoples thoughts on what SLC to use.

Are some better than others ?

I've got about 34m2 to do if that helps
 

Sean Kelly

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You are going to get a load of different answers Kevin. I personally use BAL Level Max. It's quite a watery mix but you still need to use a float to level it out. You will probably need about 9 bags of it.......but buy 10 to be on the safe side.
 
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Rookery

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I like Mapei so I'd use their Renovation Screed but there are lots to choose from.
 
Q

Qwerty

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I do like Mapei Ultraplan Renovation screed too.

I think @ISOMAT UK make a suitable SLC too?
 
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Flintstone

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You are going to get a load of different answers Kevin. I personally use BAL Level Max. It's quite a watery mix but you still need to use a float to level it out. You will probably need about 9 bags of it.......but buy 10 to be on the safe side.

I’d be using about 18 bags!
No way 10 bags Sean.
 
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Spare Tool

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Just done 36sqm ufh, 6mm over wires this week, used 24 x 20kg bags of Rocatex
 
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Rookery

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About 14 bags.
Area x average depth x 1.7 / bag fill + a couple jic
Therefore:
34mtrs x 5mm x 1.7 / 25kgs + 2 = 14
 
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Spare Tool

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Never works out as it should using calculations though, i always get 1 1/2 sqm mtrs per 20kg bag at 6mm thick
 

LEE MAC

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On a flat floor a bag typically covers 5mts @ 3mm deep, include the cavities around the ufh and a good guide average would be about 2mts per bag.
 
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Spare Tool

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Maybe I'm doing 7-8mm deep then, spoze by the time I've stuck the 6mm insulation board strips as guides, the glue and sticking it on the ufh mesh could raise the strips a mill or two, since I've been doing it this way I consistently get 1.5m per bag..
 

LEE MAC

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Andy your not far out at all with that measurement, you’re better looking at materials than looking for them in my book.
 
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Spare Tool

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Andy your not far out at all with that measurement, you’re better looking at materials than looking for them in my book.
Nothing worse than being a bag or two short right when you need it
 
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Flintstone

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I always used to work to 2m per bag but these days I think 1.5 is probably more realistic, your better pouring more than trying to scrimp to the minimum.
 
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Flintstone

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Always have a bit more than you expect to use! Running out is such a pain, init!
 
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Dumbo

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I'm in the 1.7kg per mm per Sqm camp works for me .
 
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Flintstone

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People say 3mm over wires but it’s never really enough, 6 or 7 is about the min I find
 
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Dumbo

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People say 3mm over wires but it’s never really enough, 6 or 7 is about the min I find
I agree it doesn't run out if you do it to thin .
 

Sean Kelly

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Wow. I've only ever just gone over the 4mm wires. The tail end of the cable is buried in the substrate so is under 4mm. I've never gone above 5mm on the SLC. Don't forget BAL level max is a 25k bag. However, I will on future calculations use more. Most of my work is much smaller areas so I'm not buying in bulk. Nice idea about sticking down insulation board as a guide.
 
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Flintstone

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One I did on Friday, I needed to bring it up 10mm so I stuck 10mm squares of board in a few places and brought it up to that. The squares often look proud as they can get a raised bit of leveller sat on top of them

E810BE40-B9D1-467C-A523-C110BD4D2093.jpeg
 
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Dumbo

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One I did on Friday, I needed to bring it up 10mm so I stuck 10mm squares of board in a few places and brought it up to that. The squares often look proud as they can get a raised bit of leveller sat on top of them

View attachment 95161
Looks like somebody got a work bench in the bathroom
 
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Flintstone

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Ah that’s part of a couple of bits to be clad in delta board and mosaic.
 
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Dumbo

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One I did on Friday, I needed to bring it up 10mm so I stuck 10mm squares of board in a few places and brought it up to that. The squares often look proud as they can get a raised bit of leveller sat on top of them

View attachment 95161
I prefer to use screws to set heights as they can be set at different heights if substrate is uneven
 
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Flintstone

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On a wooden floor yes. Not so good on a solid floor!
 
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Flintstone

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If a floor is already flat and level and I’m fitting ufh I will just pour and not worry about setting height markers.
 
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Rookery

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I do it by eye and hope for the best. Usually works out though, I've been doing it like that for years.
 

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