I am currently planning to pull up my stone flag floor in a 1890s build house and to keep the floor breathable I am planning on putting down Geocel with a Limecrete screed on top.

because we are then going to use a Junkers reclaimed gym flooring, I am going to put battens ontop of the screed and then the wood flooring; as this should help vent the screed and keep "breathabiliity".

There is a joining extension with a suspended timber floor that has now had the wall between the 2 rooms removed and I plan on putting spreader plates in there for the UFH with supasoft insulation beneath.

My question is, I have 2 options for the limecrete side and am wondering which would be the better option?:

Option1,
UFH in the limcrete screed,
Pros: 1. potentially significantly more effecient?
Cons: 1. any problems the screed has to be dug up, 2. needs to be run at a different temp to the suspended floor side.

Option2,
UFH on spreader plates on the battens ubove the screed
Pros: 1. Accesible if any issues, 2. Can be run at the same temp as the suspended timber floor side
Cons: 1. potentially less effecient?


Thanks for any advice on this.
Jon

Is there anything wrong with the (I assume original) flagstones? The most obviously compatible covering with both the limecrete and underfloor heating.

Wood over any kind of underfloor heating has always seemed counter productive to me, as has an air gap.

How thick is this reclaimed floor and how well insulated the house? We have 21mm engineered oak over our UFH and it has to be run quite hot to push enough heat through the oak.

I have UFH covered with18mm engineered bamboo floor on g/f anhydride screen and on the ali covered poly spreaders on the first floor. The flow temp is generally around 38C.

The floor never feels significantly 'warm' but it is generally around 21C. However, if one walks over a section where there is no UFH piping, the floor is noticeably cooler.

Generally, the g/f (screed) retains the heat much, much better and even when the heating is off, it still feels warm.

On the f/f, the engineered boards are laid directly onto the spreader plates. The rooms are never 'cold' but the floor never feels as warm as the g/f (screed.) There are some other issues that annoy me when the heating comes on.

Obviously, the UFH pipe transfers its heat to the ali; the ali expands a micron, and as it all comes up to temp, there is clicking and popping all over the f/f for 10-15 minutes. I was told it was the bamboo expanding, but I have my doubts so have to live with it.

In the f/f bathroom, I have vinyl on the floor, so covered the spreader plates with 18mm CaberBoard onto which, is the vinyl. The CaberBoard is of course, a different dimension than the bamboo floor, but one can still hear clicking and popping. However, even with 18mm CaberBaord, the floor is noticeably warmer than the bamboo.

Bottom line is, I would not recommend the poly / ali sheets. Another time, I would use Fermacell flooring sheets or any other similar pre-grooved product. Alternatively, use the poly / ali combo and put Fermacell flooring on top to get thermal mass and a solid floor.

Awesome thanks very much for this Rex.

This is super useful.
Cheers,

I was looking at fermacell boards that come with channels cut in them for ufh pipe, then sealed in with levelling compound, timber floor on top, like

http://www.ufhsupplies.co.uk/product-category/wet-underfloor-systems/overlay-systems/cosyboard/

Other similar products available

Not sure how breathable

Hi Will,

After looking into the fermacel option it looks like it needs to go ontop of an existing timber floor. If I was to do this it would raise the floor hieght too much unfortunately as it would end up being a make up of:

timber (20mm)
femacel/ufh (18mm)
timber (20mm)
Joist

Total being 58mm above the joist

I need to somehow do the following as I have also already got the ali spreaders:

timber(20mm)
Raising panel of some sort (maybe fermacel) (18mm)
Ali spreader / ufh
Joist

Total being 38mm above the joist


I've also spoken to a fermacel provider to see if this was possible with their panel system and their response was the board my sag/ break under the foot trafic as it wouldn't be on a solid floor and the panels arn't structural.


If anyone has any other Ideas let me know? :D

Cheers all.

Thanks will,

That's actually a great solution! I don't know how I missed them. Hopefully should all work well :)

Thanks again.
Jon