ᐅ Slab foundation with concrete core activation. What are your thoughts?
Created on: 19 Dec 2017 12:37
P
Peter L
Hello everyone,
If everything goes well, we plan to start building our own home next year, in 2018. We want to contract the trades independently and also carry out some parts ourselves. Here are some key details:
Approximately 200m² (2,150 sq ft) of living space without a basement. Underfloor heating with hardwood floors and an air-source heat pump. Ideally, a photovoltaic system will be installed on the roof and an energy storage unit in the utility room (KFW40+ standard). We are planning to use calcium silicate bricks with an external insulation system made of Multipor (cost considerations). This is just for your information and not meant to be part of the discussion.
I have spent quite some time researching ground slabs and have read a lot. It puzzles me that there are so few experience reports on Swedish slabs or similar systems. There are only one or two threads on this topic in this forum. It might be due to the tendency to report online mainly when one is dissatisfied, or perhaps people don’t realize when they are building a prefabricated house. Either way, most of the posts I found are five years or older. Often, people are unfamiliar with the Swedish slab, and what is not well known or regarded as proven tends to be viewed negatively. I was able to clarify many criticisms with some research and therefore we are still leaning towards the Swedish slab, although we are not completely certain, as I have never read a clear recommendation.
1. Costs
A frequently mentioned concern is the cost, so I will keep it brief. If you include the underfloor heating and screed in a conventional slab, the cost difference becomes less significant. The Swedish slab, however, offers significantly better insulation and thus saves money over time.
2. Speed
There was a criticism in this forum that the Futura ground slab reacts very slowly. In a building with Futura on the ground floor and a conventional underfloor heating with screed on the upper floor, the upper floor warms up within about 30 minutes, while it takes around 6 hours on the ground floor. Well, concrete is much more inert and it naturally takes longer for the heat to be noticeable. The advantage, however, is that concrete retains heat longer. Each person must decide how important it is to be able to adjust the temperature quickly. I wouldn’t necessarily consider this a disadvantage.
3. Impact noise
I read briefly that impact sound insulation might be worse. How significant is this on the ground floor? Is this really the case and are there current solutions to reduce it?
4. Maintenance
I keep reading that if something breaks, it’s hopeless. I can imagine it’s easier to break open screed than concrete, but to be honest – why would you want to do that? Isn’t it more of a theoretical problem? Suppose a pipe breaks for some unknown reason, water will continue to flow and the concrete won’t dissolve or degrade because of that, right? I don’t fully understand this criticism.
5. Time savings
No criticism here, but a Swedish slab doesn’t require drying time, which speeds up the construction process and eliminates moisture in the house.
So far, I don’t see any significant negatives, though I am not an expert and can only judge based on the information I have. I would therefore appreciate an expert opinion. Are there any mistakes one can make when pouring a Swedish slab, and are there other disadvantages I might not have considered?
What would be the advantages of a conventional slab? I imagine it can also be insulated to achieve similar benefits in that respect. Then the main difference would be the drying time for the screed. Perhaps there are other considerations when building with calcium silicate bricks plus external insulation.
I look forward to your opinions.
Peter L
If everything goes well, we plan to start building our own home next year, in 2018. We want to contract the trades independently and also carry out some parts ourselves. Here are some key details:
Approximately 200m² (2,150 sq ft) of living space without a basement. Underfloor heating with hardwood floors and an air-source heat pump. Ideally, a photovoltaic system will be installed on the roof and an energy storage unit in the utility room (KFW40+ standard). We are planning to use calcium silicate bricks with an external insulation system made of Multipor (cost considerations). This is just for your information and not meant to be part of the discussion.
I have spent quite some time researching ground slabs and have read a lot. It puzzles me that there are so few experience reports on Swedish slabs or similar systems. There are only one or two threads on this topic in this forum. It might be due to the tendency to report online mainly when one is dissatisfied, or perhaps people don’t realize when they are building a prefabricated house. Either way, most of the posts I found are five years or older. Often, people are unfamiliar with the Swedish slab, and what is not well known or regarded as proven tends to be viewed negatively. I was able to clarify many criticisms with some research and therefore we are still leaning towards the Swedish slab, although we are not completely certain, as I have never read a clear recommendation.
1. Costs
A frequently mentioned concern is the cost, so I will keep it brief. If you include the underfloor heating and screed in a conventional slab, the cost difference becomes less significant. The Swedish slab, however, offers significantly better insulation and thus saves money over time.
2. Speed
There was a criticism in this forum that the Futura ground slab reacts very slowly. In a building with Futura on the ground floor and a conventional underfloor heating with screed on the upper floor, the upper floor warms up within about 30 minutes, while it takes around 6 hours on the ground floor. Well, concrete is much more inert and it naturally takes longer for the heat to be noticeable. The advantage, however, is that concrete retains heat longer. Each person must decide how important it is to be able to adjust the temperature quickly. I wouldn’t necessarily consider this a disadvantage.
3. Impact noise
I read briefly that impact sound insulation might be worse. How significant is this on the ground floor? Is this really the case and are there current solutions to reduce it?
4. Maintenance
I keep reading that if something breaks, it’s hopeless. I can imagine it’s easier to break open screed than concrete, but to be honest – why would you want to do that? Isn’t it more of a theoretical problem? Suppose a pipe breaks for some unknown reason, water will continue to flow and the concrete won’t dissolve or degrade because of that, right? I don’t fully understand this criticism.
5. Time savings
No criticism here, but a Swedish slab doesn’t require drying time, which speeds up the construction process and eliminates moisture in the house.
So far, I don’t see any significant negatives, though I am not an expert and can only judge based on the information I have. I would therefore appreciate an expert opinion. Are there any mistakes one can make when pouring a Swedish slab, and are there other disadvantages I might not have considered?
What would be the advantages of a conventional slab? I imagine it can also be insulated to achieve similar benefits in that respect. Then the main difference would be the drying time for the screed. Perhaps there are other considerations when building with calcium silicate bricks plus external insulation.
I look forward to your opinions.
Peter L
You are of course right about the costs. I was still thinking of bricks, and there the price difference per brick was about double, which meant the overall difference for the house was significantly higher than here with the foundation slab. I’m not looking to waste money, so it should be affordable but not cheap.
Is this achieved specifically through the concrete core activation, or can I also achieve this with a standard construction like screed, (EPS), concrete, XPS, and similar insulation? I looked into Jackodur [1] and the system also seems interesting. This shell is reinforced and then poured with concrete. Possibly EPS and screed would be added on top. Could I also use low supply temperatures in this case?
The real question now is how smooth the surface of the Swedish slab is. If I have to do touch-ups with the screed anyway, then that wouldn’t make a difference.
Joedreck schrieb:
Especially the concrete core activation contributes to low supply temperatures, which saves real money with heat pumps
Is this achieved specifically through the concrete core activation, or can I also achieve this with a standard construction like screed, (EPS), concrete, XPS, and similar insulation? I looked into Jackodur [1] and the system also seems interesting. This shell is reinforced and then poured with concrete. Possibly EPS and screed would be added on top. Could I also use low supply temperatures in this case?
The real question now is how smooth the surface of the Swedish slab is. If I have to do touch-ups with the screed anyway, then that wouldn’t make a difference.
Lumpi_LE schrieb:
@Alex85
Very funny statement, but even a structural engineer is bound by the laws of physics...
Unlike you, he will refute a manufacturer’s claim through calculation instead of just saying “it won’t work” like a crystal ball prediction.
K
Knallkörper20 Dec 2017 11:50Joedreck schrieb:
The screed installer can't achieve 2mm over 1 meter, right?Yes, definitely.
OK, before this gets out of hand
Thanks for the note. I have made a note of it and will take it into account or discuss it with the structural engineer at the appropriate time. It is still unclear whether we will choose the precast concrete slab (Sweden slab).
What interests me much more right now is the issue of the supply temperatures and whether these are so low because of the concrete core activation or due to the insulation itself. Because if it is the concrete core activation, that would be a clear advantage. Whether it is done via the precast concrete slab or separately is irrelevant in this case.
Furthermore, I am now reflecting on the smooth surface and how problematic this actually is. Is it more of a note to be aware that some sanding might be necessary occasionally, or is it a truly bigger issue if it occurs?
Thanks for the note. I have made a note of it and will take it into account or discuss it with the structural engineer at the appropriate time. It is still unclear whether we will choose the precast concrete slab (Sweden slab).
What interests me much more right now is the issue of the supply temperatures and whether these are so low because of the concrete core activation or due to the insulation itself. Because if it is the concrete core activation, that would be a clear advantage. Whether it is done via the precast concrete slab or separately is irrelevant in this case.
Furthermore, I am now reflecting on the smooth surface and how problematic this actually is. Is it more of a note to be aware that some sanding might be necessary occasionally, or is it a truly bigger issue if it occurs?
Similar topics