Frost Protected Monolithic Slab
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- Опубликовано: 29 сен 2024
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One of the cold spots on a house is where the edge of a slab is exposed to the outdoors. This thermal bridge, is really more like a thermal runway because the outdoor air is a lot colder than the ground in winter, and hotter than the ground in summer.
No surprise that insulating the edges of slabs is one of the items on the Energy Star checklist.
Begin with a piece of ground big enough to dig a hole in, and dig that hole.
A frost protected slab doesn’t need to be dug below the frost line, depending where you live, 12, 14, or 16 inches deep is enough.
A bed of compacted gravel caps the ground under the slab, and a drainage trough should be installed in wet areas.
Lay plastic atop the compacted gravel and then pour the slab, making sure to add rebar as required.
Wrap the edge of the plastic up and install rigid foam insulation along the outside edge of the slab. This foam is about 2 inches thick, which is about R-10.
Lay another board of foam horizontally over the drainage gravel, sloping away from the house.
This piece should extend about four feet from the house to completely protect against frost heave.
Cover the foam with some sort of protective layer, such as a stucco parging or rigid panels suitable for ground contact.
Backfill the hole, and frame the walls on top of the slab.
A piece of flashing above the insulation keeps bugs and water from sneaking in.
Install the OSB, WRB, and siding; plant grass, and then take lunch-confident that this slab will stay warm and dry for a long, long time.
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Ive done my last 4 houses like this and have never had a problem
It lacks a defined drainage plane, which makes me slightly hesitant. I'm surprised there isn't a dimple mat on the front of the foam. Are you in a dry area, or do you think this won't be a problem, and why? Genuinely curious, because I do love designs that remove unnecessary items and steps.
The foam face is the drainage plane. On a basement that extends 8 feet below grade, it makes sense to use dimple mats.
For a slab extending a foot and a half or two feet-with no living space inside that part that is underground-I think is misplaced energy and attention.
Were any of those houses more than 1 story?
But you did not thermoisolate under the slab:(
Because it's inside the envelope it may add to the thermal mass and be a positive benefit.
The ground is a stable 50-ish degrees (F) when the perimeter of the slab is insulated like this.
@@ProTradeCraft that means around 10 celsius, and you have direct contact to a surface which has a temperature difference of 12 Kelvin. Should you consider installing heated floors, the difference increases. The costs of insulating under the slab are low, i think it is a must, but I'm no expert. I guess it also depends what are the climqte conditions in your are.
@@howtoscientifically7355 🤣🤣🤣🤣🤣 A difference of 12 KELVIN!?!? Do you even know what you’re talking bruh? 🤣🤣🤣🤣🤣
Why do you turn the plastic up? Won't that trap any moisture that gets onto/into your footing from draining away? Seems turning it down would be ideal. I'd also put a layer of dimpled plastic membrane just for peace of mind, to keep the footing ventilated and draining.
Foam is installed right after wrapping the footing, Water should not get in there. leaving in down will allow soil moisture to wick in.
to the author your music in this video is as useful as the sun shining in your eyes when your driving into the sunset.
editor, you mean ;)
Narrator is the word you are looking for.
You’re*** grammar and punctuation are even less useful.
Sorry you don't like music, but I do, and if I can't add music to the videos, I'm not gonna make 'em.
You know you're a sad pathetic c***sucker when you have to cut someone down for adding music to a video. From my foot to your Ass, Happy Holidays Joe Blows.
Kinda surprised you don't tell people to put foam underneath the entire slab....
Generally, that's for unheated buildings. See pdhonline.com/courses/s231/s231content.pdf
80% of slabs thermal loss is to the sides. The ground under a house is insulated by the entire house and has relitive constant temps. A under slab moisture barrier would be a better investment.
Gave me a lot more confidence when I saw that it was Steve Baczek who designed this
We only work with the best, Steve.
@@ProTradeCraft 👍
I'm concerned about the detailing on this - one of the long standing complaints I've had watching "perfect building systems" videos is the lack of clarity as to where the conditioned space starts and stops. It's for this reason, I like the REMOTE building method where the entire structure is inside the conditioned space, the vapor barrier is on the outside surface of the structure rather than among the rat's nest of detailing between floors and roofs (etc.), and the insulation is all outside the vapor barrier so that the vapor dew-point transition is always outside the wall unit.
My question with this method follows that problems always come down to how the foundation is coupled to the earth - regional code often requires foundation edge and post in direct contact with the grade. This coupling creates a huge thermal connection usually with very efficient conductors of a high mass. One of the reasons that the insulation has to be extended so far away from the slab here is rather obvious to me: the slab is conducting heat into the grade soils, and IMHO this solution is at best a band-aid for the problem - which is that heat is getting into the soil at all. In areas where frost heave is a problem, again it seems that the actual problem is that water is allowed to build up next to the structure, which this band-aid would probably make worse (although shallower).
It would seem to me that a better approach would be to insulate the majority of the slab from the ground surface, planning the bulk slab to be within the conditioned space. If code requires direct foundation contact with the ground, there is usually a wiggle room for not connecting the slab to the foundation wall but rather using a thermal break material (RPS or equivalent), then thermally breaking the foundation wall from the structure and conditioned space. This would make the temperature of the foundation wall closer to that of the surrounding soil, negating the need for this shelf of RPS.
My biggest gripe is the discontinuity of the vapor barrier - it's shown to just be covered under the edge of the RPS, typically you'd want to have the wall's vapor barrier bond to that wrap so that the joint will shed water, rather than being wicked into the foundation. Once the concrete has hydrated, I'd want to protect it from as much as I could manage to prevent degradation.
There is no drainage of surface water in the above video, only ground water up to the foundation footing. To address the frost heave, I'd want to see a very wide and deep drain, lined with filter fabric and back filled with #5 crushed stone probably a minimum of 2 feet wide and >3 feet deep, with a drain pipe at the bottom, and geotextile on the top, then covered with 4-6" of loose coarse mulch. This would promote rapid drainage around the edge of the structure of liquid water. If icing was a problem, I'd want a method to convert that solid water into liquid again to speed drainage (i.e. heat). Preferably the structure would not be designed in such a way that snow fall for example can land right at the base of the wall Barring that, I'd put a very shallow polyethylene sheet from the edge of the foundation to a drainage trench offset from the wall - sloped like the video's RPS. The idea would be to make any water build up surface-only and very shallow.
I'm sure the slab will be insulated but that detail is not covered in the video
"One of the reasons that the insulation has to be extended so far away from the slab here is rather obvious to me: the slab is conducting heat into the grade soils"
It's done so that the ground below the footing doesn't freeze and move the footing AKA "frost heave." If it's a choice between the slab conducting heat into the soil below the footing or the foundation heaving, I pick the former.
@@Thoracius You should be able to have your cake and eat it too. It's just going to require some additional thought and planning (and cost). Frost heave means you have three conditions simultaneously: 1) fully saturated soil right under the foundation, 2) freezing-cold temperatures at the foundation base edge, and 3) uneven heat loss into the ground from the building.
The frost line for North America varies from ~6" to >50". Your footing thus needs to be deeper than the regional frost line of the building, and needs to avoid losing heat from the footing depth to the outside atmosphere (thermal-wicking). This means it would need to be insulative in nature (standard 5000lb concrete really sucks at thermal resistance).
If one finds oneself building on very thermally expansive soil in a cold climate where a basement is not desired, a designer might consider the hydrofoil - it has a wing-lift structure that extends below the waves where solid calm water is and the hull is connected to the foils by poles. Since the waves at the surface only interact with the relatively small diameter of the pole rather than the entire bottom surface of the hull of the ship, the ride is much smoother.
Similarly, a designer could create a foundation that goes well below the frost line, and extend pilings up to the floor joists as in a typical pier-type foundation, insulating the piers/pilings so that surface temperature is not brought down into the warmer foundation plane. The insulated piers/pilings would stay at the cold but not freezing temperature of the foundation footing - but not conduct heat from the ground to the outside air, and with the thermal break also not from the building down into the ground. This means the whole top surface of the soil would remain at a fairly even temperature (so no shifting), and the small surface area of the piers/pilings would not give the soil enough to grab onto to move the structure.
@@Real_Tim_S A Swedish skirt shifts the thermal properties of a foundation from being a heat sink towards being a thermal mass. Though invented in the US more than half a century ago, my understanding is that these, as the colloquial name implies, have been very popular in Sweden, surely not without reason. They can also be inexpensively retrofitted to existing slab-on-grade structures. As for whether soil gets "total saturated", whatever you do to try to prevent it, time can reverse.
@@Thoracius That's the issue with the insulation around the perimeter - there is always a Delta-T during heating/cooling seasons from the inside of the conditioned envelope to the ground - so thinking of it as a "thermal mass" is wrong. It's actually a heat-sink. You are stopping frost heave by heating the ground from the interior volume conditioning - that is not an efficient design for heating the building's volume. It was conceived a long time before building science had much to do with science. Think a house with a Swedish Skirt, as a girl in a mini-skirt sitting on an aluminum bench outside in a snow storm while wearing a parka and a fuzzy hat. Her upper body will be warm in the winter, but I'm guessing you'll learn new swear words from her once she sits down... The obvious fix, if you've been to a sports game with a fashion sensitive lady, is to either stand (air gap between the icy bench and skirt-clad lady, with insulated "piers", i.e. stockings), or be a gentleman (and a hero) and put a full blanket down between the lady and the bench. Same principal with a building.
Ground water moves in the soil, and heat goes with it if it gets lost from the slab if there is no thermal break. This is a key principal behind ground-source heat-pumps. With that moving water goes any heat you lost to the cooler soil. There is far more specific energy in the ground than there is in ambient air due to that ground water - which is why ground source heat pumps are coming into fashion in North America.
Modern Building Science says:
* You need a capillary break to stop surface tension water transmission, or ground water injection into the structure.
* You need a low pressure zone to degas the sub-soil to prevent moist-air intrusion to your slab finishes, or Radon gas infiltration
* You need a continuous vapor barrier to prevent loading of your interior volume conditioning system and damage to your building's structural/finish materials.
* You need a thermal break to stop heat loss to the ground, and the air at the sides and over your building. If you have a vapor barrier, the dew-point should occur outside of that vapor barrier, and the condensed water should have a way to exit while drying the insulation material.
* You need a water-shedding, UV-and-impact-surviving "shell" to protect the insulating layer, and get rid of bulk water, snow, and hail.
Or, you need less of all four of those and wear warmer/less clothes (heating/cooling season respectively) with more outside air changes, like buildings were 75+ years ago. Your body will basically do what I described above on a much smaller, individual scale. Then you need to put your temperature/humidity sensitive items in a steamer trunk you keep near the fire place the way they used to.
I'm not arguing that the Swedish Skirt isn't a reasonable edit to an existing slab-on-grade-home where getting insulation under the building is cost-prohibitive, but to imply it's good new-build practice, I believe is dishonest.
for the best install, you should not excavate in the area within 45 degrees of the bottom of a footing or perimeter of a monolithic slab. I think this area is called angle of repose. (according to my engineer this can be slightly more or less depending on soil or aggregate type) . This is the same for typical foundations with 4ft frost wall on footings or deeper ones for a basement. The drain piping should be moved away from the footing if you want it below the footing or raise it so the bottom of the pipe is at same elevation as the bottom of concrete slab footing
Yeah, it is called angle of repose. and yeah, it's best to follow the 45-degree rule. And liberal use of a compactor will solidify the base.
Must be the only almost code compliant (Gravel should be under the perimeter) R403.3 FPSF/frost-protected shallow foundation on youtube.
That is a scary thought.
Hi, A couple of quick questions. How deep should the ridgid insulation go? Just to the bottom edge of slab or deeper? Also, should the rigid insulation be attached to the slab with adhesive or something.? Thamks
Thank you.
If I add Pex tubing in the slab and heat it for free in the fall with evacuated solar tubes would the ground retain the heat (heat sink) or would the heat loss be absorbed down? From my understanding the R value of the ground will keep the heat under the slab.
How do water drain around the perimeter if the trench it is covered with a layer of non permeable eps? Will the water pool on top of the EPS foam board before ever reaching the drain?
Groundwater rising from below drains in the drainage trench. Surface water never makes it down that seep because it drains away from the house immediately.
@@ProTradeCraft Thank you.
All that before lunch ! 😁
It's a good crew.
If you have that foam board insulation continue from below ground to the top of the concrete. How do you protect the foam from the elements and damage?
With some sort of protection board. There are many options, including PVC panels.
ruclips.net/video/opmk9NoN9xE/видео.html
By using stucco or rot resistant panels. Was discussed in the video
Why would you block the weeping tile with ridged foam?
The perimeter drain carries away groundwater. The rigid foam above, is sloped away from the house to direct surface water away, and protects the footing from frost.
ProTradeCraft perfect!
What the hell did people do a hundred years ago for their foundations? Answer: Paid a hell of a lot less for them.
What's your point? A lot of houses didn't have foundations 100 years ago, or they used wooden beams that rotted.
"and then take lunch" 😂
Should you put foam under the slab as well?
should I? I'm kind of busy.
It depends on whether you should or not.
With the foam skirt surrounding the slab, the slab will stay around 60 degrees or so, which wouldn't require very many Rs to combat
wouldn't a drainage tile at the sloped end of the insulation board be better? any moisture from above would follow that slope wouldn't it?
Footing drains carry ground water away from the footing. The sloped insulation board directs bulk rainwater away from the house. Two ways to control two types of bulk water.
@@ProTradeCraftwhere do the underground pipes vary the water? Do I need a sumpump on exterior of house?
16”?? Try 60”
I live where the air hurts my face.
Steve I am in Warwick RI and would like to utilize this frost protected slab protocol for my 32/32 two story garage.
Any suggestions on how to achieve this in RI
THANKS
Doug
Just make sure you use the right amount of insulation as specified by the code. Better yet, use a little more. Building Science Corporation recommends R-10 for basement floors and R-20 for basement walls. I suspect that would translate to R-10 for the slab edge, which is 2 inches of XPS.
1:38 Note: the 2 x 6 bottom plate extends over the side of the slab by at least the thickness of the outside foam (aka thermal break).
Sure, but every stud in every wall is also a thermal break. The better solution-which most people will NOT do- is to also cover the walls with exterior insulation.
you installed that sloping foam wrong, do you wanna know why? 1:08 you dont know
the suspense is killing me
Unprotected foam and plants, roots, future digging? Seems overly optimistic.
I mean, I hope it goes without saying that for a shallow frost-protected slab, it's probably a bad idea to plant shrubs right next to the house.
If you dig a hole and find a shuckload of foam in the ground, maybe stop digging and try to fix your mistake?
@@ProTradeCraft Makes sense. Some thoughts...
(1) Roots find their way a considerably distance. Lots of people have plants/trees 8 to 10 feet from a house, and that is considered reasonable, depending on the spread of the canopy. Roots can easily go that far.
(2) After a house is sold, how often is this kind of detailed knowledge about a slab passed along? (Yes, maybe it should be!)
(3) Right, a savvy / conscientious landscaper or homeowner who comes across a lot of foam will pause and think about it. Unfortunately, there are many that might have an incentive to not say anything.
(4) When it comes to "what is right and wrong", some people "pass the buck" and say "I acted responsibility; it was that downstream person who messed up". Easy to say, but it isn't this simple. The "downstream" / future person may not have the knowledge the first person had. Again, it is easy to say "they should have known better". Maybe, maybe not. Maybe their whole industry isn't yet up to speed on new designs? Engineering has to factor in realistic human behavior (warts and all) and laws, codes, etc.
(5) For a new slab technique to stand the test of time, it isn't just an "engineering" question -- it is also a "real world" maintenance question. There are well-known practices, such as "call before you dig", "plant trees according to the canopy size", and "plan for water movement", and "don't damage waterproofing membranes". How many more do we need to add?
(6) Putting ethics ("should haves") aside... when a mistake happens, who pays? Often the homeowner. This is why homeowner wants the engineer, designer, builder to have aligned interests.
All in all, I like innovative building techniques, particularly ones that save energy. But if they are easily damaged, then maybe they aren't quite "there" yet.
Get rid of the music,...why just why, its distracting and makes it hard to hear...…...
Dan,
How do you make insulation for manholes of the drainage system? The grain tubes are insulated with a skirt around the house, but I afraid hatches could be frost bridges...
Regards, Irina
1:16 cover the foam with what? Something strong enough to withstand a weed eater string
Does anyone actually have grass growing up to their foundation? Don't people who use weed-eaters have flower or shrub beds around the foundation?
Pressure-treated plywood, fiber-cement panel siding, stucco, and surface-bonding cement are three traditional examples, PVC cladding panels is another.
@@ProTradeCraft Ive seen old shingles placed along fence lines and around houses to prevent grass from growing. Traditional "flowers or shrub beds" are for women or guys who like to weed, not men who could care less.. 16 gauge SS would be required to survive the weedeater. But you could also place a protective barrier there right before weedeating and move it along while trimming.
I like to video but kill the music next time
I killed it! Now I have to buy a new computer screen.
No.
Replace the rigid foam on the wall with drainage foam or insulation like Isodren, and you are good to go,.
Were you able to get approved by the building department up there in MA for pouring without footings down to 4' or is that just a theory you're proposing?
403.3.1 does not cover "Frost Protected Shallow Foundations" It covers "Foundations adjoining frost protected shallow foundations". You live in MA where you are required to build on footings that extend below the frost line as covered by R403.3 "Frost protected shallow foundations.
For buildings where the monthly mean temperature of the building is maintained at a minimum of 64°F (18°C), footings are not required to extend below the frost line when protected from frost by insulation in accordance with Figure R403.3(1) and Table R403.3. Foundations protected from frost in accordance with
Figure R403.3(1) and Table R403.3 shall not be used for unheated spaces such as porches, utility rooms, garages and carports, and shall not be attached to basements or crawl spaces that are not maintained at a minimum monthly mean temperature of 64°F (18°C)."
In MA you are required to pour footings 4' below grade.
You're right, now that I read it carefully it doesn't; the mean temperature in the code is of the building not the outside air. I never built insulated shallow footings/foundations or slabs because I will never be able to trust in the quality and integrity of the structure say 50 years from now. I always thought that the code set the 64deg for outside temp not building temp. Again I would NEVER rely on a band aid type of system to last over a 100 years down the road. If you've ever seen termites you'd cringe at any thought of relying on such a system. Not to mention physical damage by equipment since the foam would be at a shallow depth and is extremely fragile. Also having lived among trees I grew up to respect their ability to cause havoc even on solid structures let alone flimsy foam.
I've personally built dozens of basements 9-12' deep from forming to pouring large 5000sqft houses with a couple of helpers but never a slab on grade house. The shallowest I've built was crawlspaces.
Related to your post, I stand corrected and you are accurate in your illustrated explanations. I did learn from your illustrations the method of installing insulated frost protected shallow foundations so I'll keep it in my memory but it will always be just that, a memory.
Thank you. Cheers.
Made in USA (what do you make here in the USA?)...
You have two main issues, first environmental issues since you're by the river and second flood water caused by the overflowing river.
Regarding the first issue; I would imagine that Montana would have strict EPA rules but the best place to get information is to check your local municipal building department. They would be able to best advise you how to handle your septic system.
You have to also be concerned about flood water and your base flood elevation. Base flood elevation is a height calculated by FEMA that marks the level of floodwater during a 100-year storm. Check your local municipal building department or property records to find your existing base flood elevation or you can check directly with FEMA To find your advisory elevation; type in your address at FEMA's advisory elevation website.
I would not build a basement by a river, lake or ocean you'd be battling water all your life. If you have to build by the river I would raise your house and keep the ground level as garage only with ability to have flood water pass through with no damage to belongings. As I said you have to check with your building/zoning departments (zoning for height issues since you're raising the building) for best answers. Keep in mind if you raise your house, your insurance would be lower. Also you'd have the benefit of better river views...
Radiant heat is always better than a furnace in climates like yours. I would invest in a combi boiler for your hot water and heating needs.
Good luck
@@madeinusa5201 Have a company build a swimming pool just outside the footprint of your new construction. Then build the foundation inside of the swimming pool. ;D
@@madeinusa5201 What does structures in the FP mean?
No insulation under the slab? 😂 WTF
When the edges are insulated, the delta T between inside and under the slab is very small, so very little value is added for that money. But feel free to insulate the whole under slab area if you want to.