Slab Foundation in Cold Climate // Problems

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Slab foundations are cost-effective. However, they have some issues. The houses built on a cheap slab foundation are neither energy-efficient nor durable. Slab foundations in a cold climate are complicated. In this video, you learn the basics about slab foundations and see a proper slab foundation, which I recommend.

00:00 Slab foundation origin
00:36 Cheap slab foundation
00:55 Slab foundation thickness
01:09 Floor heating system
01:46 Wasted energy
02:18 Insulation problems
02:52 Durability problems
04:03 Sometimes lose and always win
04:12 A proper slab foundation
05:40 Beam foundation
05:52 Thank you
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1:27 that is a fundamental misunderstanding. Increased heating of the house doesn't start when the house get colder. Any decent temp regulator for a house relies on outdoor temperature, with more or less influence from inside temp. As it relies on the outside temperature it starts earlier, and doesn't increase more because the floor is slow.

Also, you personal skepticism is no reason for down playing a solution that have served over the years without the movement related issues you mention.

To add to this 'moisture' problem, most are built on 2-4 mm grovel that definitely breaks water movement. Also, many put in vapor barriers between the layers to stop ground gases to get into the house.

eleson
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I believe the basic premise of this video is incorrect. A insulated raft/slab foundation installed as per a structural engineer’s specification will not suffer from any of these issues highlighted in this video. In the UK a structural engineer’s PI insurance would be on the line if the structure of the foundation started to degrade within 10 years. Not sure why Marek describes the insulated raft/slab as being cheap, it is no cheaper than a block and beam foundation to construct a foundation this way.

NickLaslett
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Thanks for sharing your knowledge about foundations. I have a lot to learn ....but am impressed with the research you have done. Best Regards from the state of Washington, USA.

dogonit
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No, your "better slab" is not better. You have thermal bridge between foundation and the wall (and heated floor). Just use XPS of appropriate thickness and density in the first design and you will have no problems whatsoever. Of course, you need to rebar it appropriately - ask engineer to do calculations. For heating you just need smart controller which will know the time needed to heat the mass correctly to not overheat. Can use outside temp to do preemptive heating and even weather forecast. Then you can use cheaper off-peak electricity to run your heat pump at night.

dmitryplatonov
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What about 1x3 foot footing, 1x2 foot pony wall, gravel & weeping tile on outside of footing, backfill inside of footing, vapour barrier & foam on inside sand, heat pex, rebar, 6” pad. Foam outside wall & slope 4’ foam away from wall around exterior.

DinorwicSongwriter
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There is ASCE 32-01 regulating construction of First Protected Shallow Foundation. This document highlight s all these issues.

Darrida
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Marek, another informative video. You make some interesting points and I am sure some folks will have many comments in response.
It is interesting that many builders still put rebar or steel into concrete. Why?
Long term, the steel will eventually oxidize and deteriorate the surrounding concrete.
If the design, the materials and the installation are correct, there should be no need to install steel reinforcement, especially for light construction which residential buildings are.

dc-wpoc
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You're definitely wrong about most of this. The control loop for in-floor heating doesn't just measure the air temperature of one room at one point, it measures the temperature into the loop and out of the loop in order to tune the PID. I've never seen a construction crew fail to correctly compact the ground, so that's not a real issue. The bearing capacity of EPS foam is higher than any soil, so it's actually stronger to use foam than to put a slab directly on the ground. Also, in a cold climate you absolutely must have a complete thermal break from both the ground and the air, on the outside of the structure. In your diagram you show a slab directly against the ground (which would be 1-2C) with concrete block bearing directly on it with no thermal break. So your walls will be extremely cold. The only advantage to your design is that dumping a ton of heat into the ground raises the frost line.

canonicaltom
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But isn't your slab has a massive thermal bridge on the sides? Bottom slab would always be cold, the same as the ground, and it'll absorb the heat from the outside walls and your house.

alteragnostik
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How is the exterior insulation (in the ground) protected from moisture so as not to reduce its effectiveness (that you talk about)

positiveaspect
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Even though it takes longer to initially heat a bigger slab, can't that be a good thing? If it is insulated properly, it's going to stay warmer for longer.

joshuasmith
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All the foundations you talk about use so much concrete, but it's such a high energy material. Any foundations without it would be appreciated!

kurtbognar
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What happens if water gets in between the two layers of concrete in your example? Since there is hydro isolation at the bottom- that seems alright, but if due to flooding (burst pipe or something similar) water gets into the insulation from the top- be it seeping through concrete or through the edges?

Zendo
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What about a dual, or even triple pour with embedded foam boards, like tilt up walls? heat pipes in the top layer, no foam over footings.

Trident
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Idealy when you compact soil very well like engineer is specified in project and you add one plastic under EPS/XPS like radion stopping plastic then i think you dont have this issue with water migrating into your isolation and ruining R- value(or U value) over time. Why slabs brake is that contractors wants to cut corners.

revo
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For your improved slab the lower slab is not needed, just use stone.

andrewmiller
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It seems like you're speculating and don't have proof...

psolsrud
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Heya! Just came across your channel, love it! I've watched the beam foundation video as well as the slab foundation and you mention you recommend beam foundation. But I haven't really understood why. Wouldn't you get better insulation values with a proper slab foundation as well as less risk for settle, as load is spread?

jorelstone
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Spray foam under the slab 2-3” it’ll be a continuous strong seal all the way through you can even spray the side of the slab after it’s poured

jimmyb
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You need heatloss into the ground to prevent frost heave of the foundation

troids