Non-structural frost wall

[Ryan Schultz]

I know per section 1809.5 that the supporting structure needs to be below the frost line, but are there requirements, or minimum requirements for an insulated frost wall that would protect the building's slab from heaving?

Although it might hard to construct this in the field, as illustrated below, could you theoretically just put rigid insulation between the posts to protect the slab?

 

[Ryan Schultz]

I should have clarified, the exterior wall will be supported by girts, not the slab.

 

[RLGA]

If the IECC is adopted, then the perimeter of the slab must be insulated to the depth indicated if in Climate Zones 4 through 8 for unheated slabs, and for all Climate Zones if the slab is heated (2015 IECC Table C402.1.3).

 

[Ryan Schultz]

sounds good. So that "insulated wall" could be merely rigid insulation, if you could make it work in the field. Correct?

Or in other words, there's no structural requirement for that "insulated wall" if indeed, it's not structural.

 

[RLGA]

sounds good. So that "insulated wall" could be merely rigid insulation, if you could make it work in the field. Correct?

Or in other words, there's no structural requirement for that "insulated wall" if indeed, it's not structural.

If the posts are the only load-bearing elements, then the below-grade wall is there just to support the required insulation.

 

[Mark K]

Am confused and concerned. Am I reading this right. The treated post below the concrete will ultimately rot.

 

[RLGA]

Am confused and concerned. Am I reading this right. The treated post below the concrete will ultimately rot.

Treated wood is permitted for foundations by the IBC. Think of them as wood piles or piers.

 

[JCraver]

So it's a pole barn? Can you call it a farm building? Gets you out of the code requirements (in IL, anyway).

 

[JCraver]

sounds good. So that "insulated wall" could be merely rigid insulation, if you could make it work in the field. Correct?

Or in other words, there's no structural requirement for that "insulated wall" if indeed, it's not structural.

If it's an IECC project, insulate to the bottom of the slab and horizontal under the first 18" (6" slab + 18" under = 2', per Table 402.1.2) of the slab edge and be done . Any interpretation of the code that would ask you to dig a trench just to put insulation in for that type of structure is way wrong.

 

[RLGA]

If it's an IECC project, insulate to the bottom of the slab and horizontal under the first 18" (6" slab + 18" under = 2', per Table 402.1.2) of the slab edge and be done . Any interpretation of the code that would ask you to dig a trench just to put insulation in for that type of structure is way wrong.

View attachment 2999

The image is in reference to the residential requirements of the IBC, but the same conditions also apply to the commercial requirements in IECC Section C402.2.5.

 

[Ryan Schultz]

It is a 3,700sf S-1 repair garage occupancy.

 

[Mark K]

Irrespective of what the code may allow, treated wood just delays the rotting of the wood. While there are some examples of old wood poles that have not rotted you will find many others that have problems.

In the proposed design it would be easy to pour a perimeter concrete wall.

 

[JCraver]

Sure it'd be easy - but it'd be much easier to punch some holes and stick a post in them. Not to mention how much cheaper it'll be.

 

[Ryan Schultz]

Logically, it seems like the soil below the slab in the following section could still heave and thus creak the slab.

Am I missing something? Not sure why this is an acceptable approach code-wise.

 

[RLGA]

Logically, it seems like the soil below the slab in the following section could still heave and thus creak the slab.

Am I missing something? Not sure why this is an acceptable approach code-wise.

The soil under the slab is not exposed to freezing temperatures. The insulation at the perimeter is to prevent thermal bridging to the exterior.

 

[Ryan Schultz]

Just for future visitors, the following thread adds perspective on insulating slabs...
https://www.thebuildingcodeforum.com/forum/threads/heaving-slab-with-insulation.25066/