Electric UFH, Insulation and Ditra

[eddiem]

Hope someone can help. I'm having my kitchen refurbished and want to install UFH. The current floor looks as though it is tile on tile as, at the hall door threshold, it sits the thickness of a tile plus adhesive proud of the hall flooring. I also suspect that the concrete floor substrate is not insulated as its a 1930's semi. I have therefore asked the builder to dig up the current floor slab and install a new, insulated one. His initial proposal was to dig out, install 100mm kingspan insulation, 100mm single pour concrete slab over that, electric UFH with a flex SLC and then tile on top. I've told him that the concrete slab should really have 3 months or so to dry before its tiled over and that on top of that, I also don't want to have to heat up the slab before I get any heat benefit on the surfce of the flooring. He has therefore suggested that we put some Marmox board over the concrete slab before we lay the UFH as that will act as a waterproof layer and also insulation. I think I'm reasonably happy with that but wondered whether a Ditra style mat layer may also be necessary and if so, where in the build up?

 

[Concrete guy]

The marmox is a sensible suggestion.

I personally see no advantage or requirement for an uncoupling membrane (Ditra) in this specification as long as the newly poured slab is completely dry.

 

[eddiem]

Sorry, should have been clearer. I don't think we will have time to let it dry completely. I suspect it will get 2 weeks max before he's ready to tile. Basically, would love t leave it for a few months but can't live without the kitchen for that period of time.

 

[Concrete guy]

Well in that case, Ditra was designed for use in fast track building to allow green screeds to be tiled so in those circumstance there is an upside for decoupling.

You may have a long delay before you could consider using the UFH though as you still want the slab to dry naturally.

 

[eddiem]

Thanks, I'd have to accept that I guess. So what would the build up be?

concrete slab
Marmox
UFH
SLC
Ditra
Tiles

 

[Ajax123]

If you are installing a complete new floor wold you ot be better going for an in screed system. This would be more efficient and could be either electric or warm water.

 

[Concrete guy]

Thanks, I'd have to accept that I guess. So what would the build up be?

concrete slab
Marmox
UFH
SLC
Ditra
Tiles

Just look at that list of layers. That's why I don't like Ditra with UFH - just too much going on.

I'm with Ajax, with the extent of works you're undertaking a wet system is more logical and far more cost effective long term.

 

[Ajax123]

To be fair I could save you a wad of cash on the builders spec as well. If you want to look at that le me know.

 

[Uheat - Keith]

Yes, the Elektra VCD17 in-screed system is a way to go, 50mm minimum screed on top. Remember this system is a storage type system, for use with the power going into the cables overnight, slowly releasing the heat over the course of the day..

Under Tile Systems are a 'direct acting' system where the heat comes through in a shorter space of time.

We also supply water systems from here, 65mm screed needed on top of pipes, nationwide delivery.

Warm regards, Keith.

 

[Ajax123]

What cable size is your Electra vcd17 system Keith?

 

[Uheat - Keith]

As per Alan, bit more info on our Elektra VCD17 cables.
The Elektra VCD17 cable is 5mm x 7mm. It has an output of 17 watts per metre. 22 sizes made and stocked here by us.
Different size for different size areas depending upon spacing of the cables.

Two or more of these Cables in a large area can be joined together in parallel in a low level service box.
Hope that is of some help.

Warm regards, Keith.

 

[eddiem]

Thanks everyone for the advice, its given me lots to think about.