UFH/Screed for sloping floor

[markashley]

Hi,

I am going to be screeding my kitchen floor and plan (budget allowing) to have UFH installed.

The floor extends 5.5m out from the house but has a 2" gradient on it.

My thought was to just let the flow screed sort out the difference but will this cause problems with the heat from the UFH (if I go ahead with it)

Or I could increase the depth of the insulation (currently planned to be 150mm PIR), but it would be nearly impossible to match such a small gradient (10mm in every m).

The width of the kitchen is 12.5m so wouldn't really want to use any self-levelling compound prior to laying the insulation.

And advice or thoughts would be welcome. Thanks in advance.

Mark.

 

[Mr Chibs]

I think I'd just make it up on the screed. Yes, the pipework may have a thicker amount of screed to pass heat through, but when it's working this won't really be noticable.

What depth screed will you be having?

Alternatively, you could correct the slope before you screed lay the insulation, but you wouldn't want to SLC 12.5m!

 

[markashley]

I think I'd just make it up on the screed. Yes, the pipework may have a thicker amount of screed to pass heat through, but when it's working this won't really be noticable.

What depth screed will you be having?

Alternatively, you could correct the slope before you screed lay the insulation, but you wouldn't want to SLC 12.5m!

Thanks for the thoughts.

The screed was designed to be 75mm poured on top of 150mm PIR.

If we made it up with screed, likewise if we tried to put down some SLC before the insulation, then a quick bit of math would indicate that we need 1.7m3 to cover the area.

The other option could be to use something like MOT with some sand on top just to take some of the height out of the bottom but I don't know if this would be good practice.

Mark.

 

[Mr Chibs]

That's a bit of screed.

So are you saying MOT on top of the slab to level, then a sand blinding?

Could you not go back to your idea and increase the insulation another 40/50mm at the deepest end, then a step down to 25mm etc, then you won't be needing loads of screed. You could tape up the stepped edges of the PIR.

I have liquid screed, around 65mm thick, all as been good since it went down.

 

[markashley]

That's a bit of screed.

So are you saying MOT on top of the slab to level, then a sand blinding?

Could you not go back to your idea and increase the insulation another 40/50mm at the deepest end, then a step down to 25mm etc, then you won't be needing loads of screed. You could tape up the stepped edges of the PIR.

I have liquid screed, around 65mm thick, all as been good since it went down.

To be honest, I think that is my preference too. Just worried about the screed flowing into the gaps of the insulation where I step it up as it will have a membrane barrier and I might not be able to get the membrane right up into the corner. I suppose I could try my best to smooth out these steps by cutting the insulation a little.

Mark.

 

[Mr Chibs]

You need a perimeter PIR up stand and foam compression layer, around the walls, so it will be easy to make it screed proof.

Get a foam gun and some aluminium duct tape and seal every joint, all will be good.

Going to be a great kitchen at that size.

 

[markashley]

Hi mate. Yeah good thinking. I think I’ve got a plan.

Thanks for the support. It should be great when done. We started pre covid and got to the point of no return, now all the price rises have meant we can’t afford to finish the original plans so had to cut back in areas.

It’s little problems like these that now send me over the edge lol.