Renovation of concrete floor without basement

Hello everyone!

I have an area of about 8m2 in the entrance area of my house with a kind of anteroom.
Here is a small coat rack and the doors to the ground floor rooms (workshop and heating cellar).

I had the door replaced and now that this leak has been fixed, I want to address the floor. The substructure consists of about 50cm thick concrete from the year 1899, underneath is a damp ground – there is no basement below. No moisture is visible on the concrete and the old parquet in the workshop is not warping, so I assume the floor is quite dry.

I now want to insulate this anteroom because it is always very cold here – currently there are only 2mm thick PVC boards glued to the concrete. There are only 45mm available in total.
Can someone recommend a suitable insulation? Since it is the entrance area, it must be able to handle moisture as well... would underfloor heating be advisable? The heat could then rise and also heat the entire staircase... currently there is no radiator here.

Thank you very much, Nick

Hello Nick. You have actually already communicated the most important parameter: there is no rising damp. I would do it like this: grind (or have it ground) the concrete surface, prime with dispersion primer, and then cover with ceramic porcelain stoneware tiles. A so-called foil heating is embedded in the mortar bed. This is an approx. 2mm thick electric heating mat. Depending on what you prefer, this foil heating can be used only as floor heating or, with a thermostat, as a regulated room heating. The advantage of this heating system, which has proven itself in practice, lies on the one hand in the low construction height, but especially in the very fast response time. Turn it on, and the floor is warm after just a few minutes. Personally, I think this construction option should at least be considered once to see if it could be a solution approach for your home as well. Simply research >Fußbodenheizung - Heizfolie< on the internet! Everything else would either be technically complex to implement or would not achieve the expected success. Because only with insulation, a floor cannot and will not warm up. --------------------- Greetings: KlaRa

Hello Klaus Thank you very much for your detailed response! I already have a (connected to the oil heating) underfloor heating in the bathroom. Would it also be possible to use an underfloor heating with water hoses? Because the heating room is directly adjacent to the anteroom, this would be easy to accomplish... Or is the existing space under the door not sufficient? I once read that these electric underfloor heating systems are quite power guzzlers...? Many thanks, Nick

Hello Nick.
On the one hand, a foil heating system is a special design because it is not listed normatively in the screed standard DIN 18560 Part 2. But it has proven itself in practice and is thus "state of the art."
The electrical consumption of such foil heating systems is regularly overestimated.
If this foil heating system is to function as room heating, then consumption and the associated costs are inevitable regardless of the type of heating.
However, if there is already a warm water underfloor heating system and a connection option for it, then one can indeed choose this way if the installation height is available. And 45 mm is definitely not enough for that.
What would then be necessary according to professional rules is a screed on an insulation layer, into whose cross-section the heating elements are installed.
That means: approx. 40 mm insulation and 55 mm screed (as calcium sulfate flowing screed) + top covering.
Again, as a special design, a composite screed could also be chosen in which the heating elements are embedded. This form also works but, as mentioned, is a special design and associated with disadvantages, not least because the insulation underneath is missing.
I had already considered all this in my deliberations.
I do not know the situation on site either.
If the execution, as described by you, would involve "slotting" the floor slab to be able to lead the heating elements under the door, then this idea should be discarded. Because it is not for nothing that it is said (with focus on concrete ceilings): "Hands off static components."
Which is why I suggested the foil heating under porcelain stoneware tiles.
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Have a nice Sunday: Klaus

Great, thank you very much Klaus!!