ᐅ Slab foundation with concrete core activation. What are your thoughts?
Created on: 19 Dec 2017 12:37
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Peter LHello 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
The only real disadvantage I can think of is the possible lack of sound insulation.
I share your other views. Due to the thermal mass, comfort can also increase.
The pipes are pressure-tested before the concrete is poured, so errors are minimized.
If it costs only a little more, I would definitely do it.
I share your other views. Due to the thermal mass, comfort can also increase.
The pipes are pressure-tested before the concrete is poured, so errors are minimized.
If it costs only a little more, I would definitely do it.
T
toxicmolotof19 Dec 2017 15:55I haven’t dealt much with the Swedish slab since it wasn’t an option for us, but I want to share some questions and points you might want to consider:
Although it’s not common to remove a heated slab floor, it is possible with a traditional concrete slab if needed.
With your air-to-water heat pump, you don’t need a fast-responding underfloor heating system. Your heating system will be designed so that quick changes aren’t possible. It relies on being generally slow and continuous.
No one prevents you from properly insulating beneath a standard concrete slab either.
I can’t comment on the costs or potential savings.
Although it’s not common to remove a heated slab floor, it is possible with a traditional concrete slab if needed.
With your air-to-water heat pump, you don’t need a fast-responding underfloor heating system. Your heating system will be designed so that quick changes aren’t possible. It relies on being generally slow and continuous.
No one prevents you from properly insulating beneath a standard concrete slab either.
I can’t comment on the costs or potential savings.
Peter L. schrieb:
Okay, if a pipe breaks for some unexplained reason, the water would still flow and the concrete wouldn’t get damaged by it, right? I can’t fully understand that criticism. If the risk or costs from that were considered high, this topic would probably have been rejected already in commercial construction.
Joedreck schrieb:
The pipes are pressure tested before pouring the concrete. ... what exactly does that mean?
https://www.instagram.com/11antgmxde/
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B
Bieber081520 Dec 2017 08:22If the precast concrete slab is more expensive, then I would choose conventional construction.
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