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Slab in unheated garage

I noted in first post that this was a post frame/pole barn. I learned post frame is not subject to the prescriptive requirements of the IRC. It's an IBC type U building.
 
What "moisture" are you seeing that is not water?

Water is all H2O, regardless of phase. In the world of building science, if we want to talk about a specific phase of water we say phase [vapour/liquid/ice] water. We rarely refer to moisture as it means either vapour or small amount of condensation.

With this in mind, I assume you are indicating that there would be phase vapour water contained in the soil that can cause frost, I would question how often this happens. Typically, there will be an intermediate phase change to phase liquid water before the ultimate phase change to phase ice water. There are conditions that can be present that causes deposition where phase vapour water undergoes a phase change directly to phase ice water, but the conditions are extremely demanding for this to be able to happen naturally.

The capillary force holding water is not just present in clay, but any soil particles small enough to ensure the adhesion of the water molecules to the soil particles overlaps sufficiently to defeat gravity.
Moisture meaning adsorbed water instead of free water. You assume incorrectly. You can try to talk down to someone else; discuss phase of water all you want in building science but this is a geotechnical issue, not vapor drive. In geotechnical engineering there is certainly a difference between bulk water and moisture. But, hey, thanks for a bunch of information from 6th grade science completely irrelevant to frost heave. You have a building science hammer so it must apply to a geotechnical nail!!!

Capillary force is present in all fluid/solid interactions. But clays are different from granulars. The quick and easy answer is the size and shape of the particles. Clays particles are flat like a playing card and stack closely. Frost heave occurs when adsorbed water between the playing cards freezes and creates a frost lens driving the particles apart. Granular soils have relatively enormous spaces between particles which allow free draining of water and also allow the frost somewhere it can expand (kinda like air entrainment). It does get much more complex, see your local geoengineering professor for a more detailed answer. Try not to mansplain to them, they, understandably, don't like that much.
 
Moisture meaning adsorbed water instead of free water. You assume incorrectly. You can try to talk down to someone else; discuss phase of water all you want in building science but this is a geotechnical issue, not vapor drive. In geotechnical engineering there is certainly a difference between bulk water and moisture. But, hey, thanks for a bunch of information from 6th grade science completely irrelevant to frost heave. You have a building science hammer so it must apply to a geotechnical nail!!!

Capillary force is present in all fluid/solid interactions. But clays are different from granulars. The quick and easy answer is the size and shape of the particles. Clays particles are flat like a playing card and stack closely. Frost heave occurs when adsorbed water between the playing cards freezes and creates a frost lens driving the particles apart. Granular soils have relatively enormous spaces between particles which allow free draining of water and also allow the frost somewhere it can expand (kinda like air entrainment). It does get much more complex, see your local geoengineering professor for a more detailed answer. Try not to mansplain to them, they, understandably, don't like that much.
You're probably right. I don't know nearly enough about geotechincal engineering to be considered an expert. I'm sorry you misunderstood what I was referring to in my original post. I was referring to water as being the molecule and assumed most would come to the conclusion I would be talking about water absorbed into the soil since trying to place a concrete slab over a body of open water (bulk water as you put it), doesn't sound like your typical residential garage. I'm glad we were able to clear up the miscommunication.
 
This is a fickle business. No way will my building department permit a slab in an unheared garage to not be frost protected.

On the other hand, what they'll accept for a shallow frost protected foundation for unheated building is much less than what I read the code requiring. A 30x36 haunched slab 8" thick and 12" wide at perimeter with 8" vertical and 24" horizontal 2" XPS, nothing like any of the guidelines.

Paraphrasing, "...we don't need to go minimum 12" deep here.. "

At the end of the day, the ground is all coarse sand for many feet and site is a gentle slope, so I don't have real concerns about frost heave, so will accept making it simple as possible.

Frustrating interpretations vary so wildly from jurisdiction to jurisdiction.
 
Moisture meaning adsorbed water instead of free water. You assume incorrectly. You can try to talk down to someone else; discuss phase of water all you want in building science but this is a geotechnical issue, not vapor drive. In geotechnical engineering there is certainly a difference between bulk water and moisture. But, hey, thanks for a bunch of information from 6th grade science completely irrelevant to frost heave. You have a building science hammer so it must apply to a geotechnical nail!!!

Capillary force is present in all fluid/solid interactions. But clays are different from granulars. The quick and easy answer is the size and shape of the particles. Clays particles are flat like a playing card and stack closely. Frost heave occurs when adsorbed water between the playing cards freezes and creates a frost lens driving the particles apart. Granular soils have relatively enormous spaces between particles which allow free draining of water and also allow the frost somewhere it can expand (kinda like air entrainment). It does get much more complex, see your local geoengineering professor for a more detailed answer. Try not to mansplain to them, they, understandably, don't like that much.
No one has mentioned water table depth or perculation of soil yet.
 
I've been called thick and dense on this, which if I were a building material could be a compliment, but so frustrating that both the local building official and a fairly experienced RDP (architect) matter of factly state the IRC requires a slab in a post frame building - a floating slab or unrestrained slab or no-foundation slab as you choose - to be frost protected. This is 2020 NY residential code, based on 2018 IRC, but I did not see any differences.

Now, if it were a bona fide agricultural building, no permit and no frost protection, but I'm not able to come close to that claim.

Just frustrating that the code is not clear and by that I mean:
"R301.1Application.
Buildings and structures, and parts thereof, shall be constructed to safely support all loads, including dead loads, live loads, roof loads, flood loads, snow loads, wind loads and seismic loads as prescribed by this code. The construction of buildings and structures in accordance with the provisions of this code shall result in a system that provides a complete load path that meets the requirements for the transfer of loads from their point of origin through the load-resisting elements to the foundation." but many say a garage floor is not a part of the building and structure and that the code required live and dead loads of garage floors are excluded from this. Perhaps buildings and structures don't include some floors but no one has pointed out that section which says some are and some are not (albeit all floors in under 600 sq ft buildings are excepted - not what we are talking about). I accept it's fine and is not a safety and welfare issue. If the only response is the building official, the architect, and I are dense and thick, don't bother responding.
 
I've been called thick and dense on this, which if I were a building material could be a compliment, but so frustrating that both the local building official and a fairly experienced RDP (architect) matter of factly state the IRC requires a slab in a post frame building - a floating slab or unrestrained slab or no-foundation slab as you choose - to be frost protected. This is 2020 NY residential code, based on 2018 IRC, but I did not see any differences.

Now, if it were a bona fide agricultural building, no permit and no frost protection, but I'm not able to come close to that claim.

Just frustrating that the code is not clear and by that I mean:
"R301.1Application.
Buildings and structures, and parts thereof, shall be constructed to safely support all loads, including dead loads, live loads, roof loads, flood loads, snow loads, wind loads and seismic loads as prescribed by this code. The construction of buildings and structures in accordance with the provisions of this code shall result in a system that provides a complete load path that meets the requirements for the transfer of loads from their point of origin through the load-resisting elements to the foundation." but many say a garage floor is not a part of the building and structure and that the code required live and dead loads of garage floors are excluded from this. Perhaps buildings and structures don't include some floors but no one has pointed out that section which says some are and some are not (albeit all floors in under 600 sq ft buildings are excepted - not what we are talking about). I accept it's fine and is not a safety and welfare issue. If the only response is the building official, the architect, and I are dense and thick, don't bother responding.
Frozen soil can support a slab. How do you frost protect a slab in an unheated space??

You're overthinking this to the point of stupidity. There are probably millions of floating garage slabs with no frost protection. The foundation is frost protected by burying it below the frost line, but the slab floats.
 
Tell that to building officials and architects in NY. I went in assuming you were correct that it wasn't required. Their read of the code is floors in unheated buildings have to be protected from frost.

I'm looking for a soils engineer to put in writing it's well enough drained (non-frost susceptible ground) that I don't need to bury $1500+ worth of foam.
 
What is foam going to do if the space isn't heated?

It seems unlikely the RDP and BO both have this wrong, I think you're misunderstanding what they're asking for.
 
They're asking that the slab in an unheated pole barn be protected from frost.

Shallow frost protected foundations in unheated buildings as permitted by (2028) IRC R403.1.4.1-3 designed in accordance with ASCE 32 have continuous foam under the slab extending beyond the perimeter of the building - approx 48" all around - to use geo-thermal energy to keep it frost free. Can work for pole park or shallow continuous footing. R403.3 for heated buildings is similar but slightly more restrictive; and there just is no prescriptive requirements in IRC for unheated buildings.
 

In an unheated building the soils below the concrete slab can freeze and lead to frost heave and broken concrete. Insulation below the slab will prevent the soils below the insulation from freezing

THREE WAYS OF PREVENTING FROST HEAVE​

Because of heat loss to the surrounding soil, heated buildings rarely suffer frost heave damage. Frost heave also is avoided by extending footings below the frost line. Pavements, driveways, sidewalks, and floor slabs of unheated buildings are not supported by footings, however. To protect these structures, you must eliminate or minimize at least one of the three conditions that lead to frost heave: reduce frost penetration; keep water out of the freezing zone; or make sure soil in the freezing zone is not susceptible to frost.

0FA0B840-ED53-47DD-AA28-027C97149BC6.jpeg

 
Apparently not for as some in NY. I'll try that, claim this is a slab and does not require a foundation; in spite of R301.1 stating all loads shall be supported on a foundation. I wish I could cite a code section that supported that exception, regardless of how obvious it may be.
 

In an unheated building the soils below the concrete slab can freeze and lead to frost heave and broken concrete. Insulation below the slab will prevent the soils below the insulation from freezing

THREE WAYS OF PREVENTING FROST HEAVE​

Because of heat loss to the surrounding soil, heated buildings rarely suffer frost heave damage. Frost heave also is avoided by extending footings below the frost line. Pavements, driveways, sidewalks, and floor slabs of unheated buildings are not supported by footings, however. To protect these structures, you must eliminate or minimize at least one of the three conditions that lead to frost heave: reduce frost penetration; keep water out of the freezing zone; or make sure soil in the freezing zone is not susceptible to frost.

0FA0B840-ED53-47DD-AA28-027C97149BC6.jpeg

Just to be clear, this is not a code requirement, correct? It seems everyone is saying it's ok and permitted by the IRC for a floor slab on ground or on grade to heave.
 
We are not saying it is okay for a slab to heave. We are saying the code is silent on what is required for you to do to keep your slab from heaving. As mentioned there are numerous options for you that you can discuss with the AHJ and/or DP.
 
Just to be clear, this is not a code requirement, correct? It seems everyone is saying it's ok and permitted by the IRC for a floor slab on ground or on grade to heave.
Point the to the millions of garages (literally) with floating slabs that are not frost protected whatsoever. There is a very clear, direct load path for slabs on grade (hint: it's right in the name).

I suspect the garage slab pictured above is the result of factors other than frost heave.
 
The code does not say you cannot provide frost protection. I would be guided by the IBC provisions.

When the slab rests on grade there is no life safety concern if there is frost heave and the concrete cracks. any loads will still be transferred directly to the ground..

If there is differential frost heave the concrete will crack. If there is enough reinforcement in the slab on grade the cracks will be small.
 
I repeat I understand it doesn't matter and I'm fine with no frost protection for a number of reasons. I'm still faced with R301.1 as well as local building official and architect says IRC (NY version) requires floor slabs have to be frost protected.
 
Would they consider a french drain to drain water from the freezing zone? Unfortunately the frost line is pretty deep in NY.
 
Yeah, it's 48" here. It's coarse sand for a long ways, and on a slope, so easiest solution is for soils engineer to say it won't freeze. Just have to find a soils engineer. (If I knew and understood a "test method" I could probably convince building official to observe test, but based on a paper reviewing many tests, probably beyond me. Trying to figure out if I could send soil samples to a lab for measuring particle size.)
 
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