Flagstones over UFH - TilersForums.com

[Ciriboyc]

Hi all,

not sure if this is really the right place for this, but here goes...

I'm renovating a small (75m²) cottage. I installed underfloor heating and the concrete slab wa poured over a year ago, so I'm guessing it's good and dry at this stage

I'd like to finish it with a flagstone floor, but my plumber is a little worried about the heat penetrating through the thickness of the flags...while he's installed plenty of ufh systems, he has no experience in dealing with flagstones so I think he's being overly cautious...but I'd really like some more opinions on this.

The first flagstones I'm looking at are Indian limestone calibrated to 20mm.

I also however have the option of locally sourced slate flags, but these vary in thickness from about 20mm to 40mm. These would be irregular shaped, but I could work them a little and the cottage is extremely 'rustic' anyway so I would be happy to use these.


The second option would be my preferred choice...I would love to get them locally, plus I like the random look of them...and also the price is definitely right! (tight budget!) but there are 2 issues I'm worried about with these flags:

1. If the plumber is worried about the 20mm...I'm afraid he'd freak completely if I mentioned the 40mm

2. If the flags are of varying thickness, I'm assuming I would have to garde them to keep things level-ish? would this affect the heating?


So, I guess my question are:

Is there any limit on the thickness/depth of Flags that can be used? (I realise responsiveness becomes an issue the thicker you go)

and

Is there any problem with flags of varying thickness?

Thanks

 

[Dave]

I’m assuming it’s a wet system and its been commissioned. It’s perfectly acceptable to use those materials 👍

 

[Ciriboyc]

Thanks David, much appreciated...you don't thing the thickness (40mm) would be an issue?

 

[Dave]

Thanks David, much appreciated...you don't thing the thickness (40mm) would be an issue?

Obviously it’ll take time to heat but once temp is in the stone then can’t see it being an issue.

 

[Ciriboyc]

Thanks, that's what I thought myself.

 

[Rae]

Youve goneout the way to fit water ufh ,choose a thinner slab,you will have ro leave the heating on all the time ,as the time it would take to get warm on 20 or 40 mm plus adhesive ,

 

[Bopster]

How thick is the screed over the ufh. Generally 50-70mm.
Another 40mm will warm but as mentioned take time, however it'll keep warm for even longer for to thermal mass so once up to temp wouldnt be any more to run than normal

 

[Lou]

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