Base plate with concrete core activation. What is your opinion?

Hello everyone,

if everything goes well, we want to start building our own home next year in 2018. We want to award the trades independently and also do some parts ourselves. Here are some key data:
Approx. 200m² living space without a basement. Underfloor heating with parquet flooring and an air heat pump. Ideally, a photovoltaic system will be installed on the roof and an energy storage in the utility room (KFW40+). We plan to use sand-lime brick with an external thermal insulation composite system made of Multipor (cost issue). This is just for your information and should not be part of the discussion.

I have been researching floor slabs for a while and also read a lot, and I find it a bit surprising that there are so few experience reports about the Swedish slab or similar. In this forum, there are only 1-2 threads on this topic. It could be because people often only report online when they are dissatisfied, or they are not even aware when they build a prefabricated house. Either way, almost all the posts I found are 5 years old or older. Often, people don’t know the Swedish slab, and what you don’t know or what isn’t tried-and-true is automatically seen as bad. I was able to clarify many points of criticism with some research and therefore we still tend toward the Swedish slab, but we are not quite sure yet, since I have never read a recommendation for it.

1. Costs
A frequently mentioned point is the cost issue, and I will keep it short. If you add underfloor heating and screed to a conventional floor slab, the difference is not that big anymore. But the Swedish slab has significantly better insulation and thus saves additional money in the long run.

2. Speed
Here in the forum, it was once criticized that the Futura floor slab would respond very slowly. A Futura floor slab was installed on the ground floor and a normal underfloor heating with screed on the upper floor. On the upper floor, the floor should be warmer already after 30 minutes, whereas on the ground floor it takes about 6 hours. Well, concrete is much more inert and of course it takes longer until the heat is noticeable. However, the advantage is that concrete stores the heat longer. Certainly, everyone must decide for themselves how important it is to vary the temperature at short notice. I would not necessarily see this as a disadvantage.

3. Impact sound
I briefly read that the impact sound might be worse. To what extent is this relevant on the ground floor? Above all, is this really so, and are there currently possibilities to minimize it?

4. Maintenance
I also keep reading that if something breaks, you might as well give up. I can imagine it is easier to tear up the screed than the concrete, but let’s be honest – why should you do that? Isn’t this rather a theoretical problem? Well, if a pipe breaks for some incomprehensible reason, water would still flow, and the concrete would not get softened, right? I cannot quite understand this criticism.

5. Time savings
No criticism, but a Swedish slab has no drying time, which shortens construction and you have no moisture in the house.

So far I see no negative points, but I am not an expert and can therefore only judge based on the information I have. I would therefore be very happy about a professional opinion. Are you doing something wrong if you pour a Swedish slab, and what disadvantages have I not considered yet?

What would speak for a conventional slab? I can imagine that you can also insulate it and thus have similar advantages in this respect. Then the only difference would be that the screed has to dry. Perhaps there are also certain things to consider if I want to build with KS+ETICS.

I am very curious about your opinion

PL

I can only imagine the possible lack of sound insulation as a real disadvantage. I share your views on the rest. Due to inertia, comfort can also increase. The pipes are pressed before casting. So error minimization. If it only costs a little more, I would definitely do it.

I have only dealt a little with the Swedish slab because it was not an option for us, but I would like to give you the following questions and notes that you can gladly consider:

Although I and underfloor heating wouldn't be discarded so quickly, it can be done with a classic slab if necessary.

With your air-water heat pump, you don't need a fast-responding underfloor heating. Your heating system will be designed so that quick response is not possible at all. Your heating lives from being generally sluggish and continuous.

No one prevents you from properly insulating even under a normal slab.

I cannot say anything about the costs or savings.

Okay, if a pipe breaks for some inexplicable reason, the water will still continue to flow and the concrete will not become saturated as a result, right? I can't quite understand this criticism.

If the risk or the costs were assessed as high, the topic would probably have already been rejected in commercial construction.

The pipes are pressure-tested before pouring.

... what does that mean exactly?

Leak test.

If the Schwedenplatte is more expensive, then I would build conventionally.