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jar546
January 26th, 2012, 11:50
Below is the code section from IRC 2009.

If a municipality deems the frost depth to be 36". Does that mean that the foundation wall must extend below 36" or just the bottom of the footer?

It is our interpretation that the foundation wall must extend below the frost depth of 36" which means the top of the footer can never be any shallower than 36" to the top of it. The thicker the footer, the deeper you must go.

How do you interpret this?


R403.1.4.1 Frost protection. Except where otherwise
protected from frost, foundation walls, piers and other
permanent supports of buildings and structures shall be
protected from frost by one or more of the following methods:
1. Extended below the frost line specified in Table
R301.2.(1);
2. Constructing in accordance with Section R403.3;
3. Constructing in accordance with ASCE 32; or
4. Erected on solid rock.
Exceptions:
1. Protection of freestanding accessory structures
with an area of 600 square feet (56m2) or less, of
light-frame construction, with an eave height of
10 feet (3048mm)or less shall not be required.
2. Protection of freestanding accessory structures
with an area of 400 square feet (37 m2) or less,
of other than light-frame construction, with an
eave height of 10 feet (3048 mm) or less shall
not be required.
3. Decks not supported by a dwelling need not be
provided with footings that extend below the
frost line.
Footings shall not bear on frozen soil unless the frozen
condition is permanent.

steveray
January 26th, 2012, 11:58
We take it to the bottom of the footing, or pier, or whatever.....because the footing is the support for the wall...if everything is smooth nothing should be "grabbed" and heaved by the frost, and it should not get under the footing...

gbhammer
January 26th, 2012, 13:04
Bottom of a Footing with 2" key.

mjesse
January 26th, 2012, 13:38
Just the bottom of the footer (footing) for any community I've ever built in.

mj

Papio Bldg Dept
January 26th, 2012, 13:50
"Bottom @ Footing" is how it is enforced here, and how every structural engineer I have ever worked with specifies the frost-protection for footings. Not to say that just because everybody else does it this way, that it should be that way, but even the ICC engineers I have worked with view it this way.

jar546
January 26th, 2012, 14:08
But,

The code specifically says Foundation Wall and ....extend below the frost line.

How can a foundation wall extend below a frost line if the top of the footer is above the frost line?

globe trekker
January 26th, 2012, 14:10
From the 2009 IRC, Table R301.2(1): The frost line depth may require deeper footings than indicated in
Figure R403.1(1). The jurisdiction shall fill in the frost line depth column with the minimum depth of
footing below finish grade.


Your jurisdiction will have to define the depths that they want to be used.

Has your AHJ done this?


.

jar546
January 26th, 2012, 14:11
Our jurisdiction did. 36" is the frost depth in most. 42 in others

Yankee
January 26th, 2012, 14:54
Some foundation walls don't even need footings. Piers don't have footings. The point is, the bottom of the built system should be low enough to prevent frost from getting underneath.

Mac
January 26th, 2012, 14:58
Frost depth is 42" here. I measure 42" from the top of the footing.

jar546
January 26th, 2012, 15:03
Frost depth is 42" here. I measure 42" from the top of the footing.

Yes! That works

Papio Bldg Dept
January 26th, 2012, 15:05
Some foundation walls don't even need footings. Piers don't have footings. The point is, the bottom of the built system should be low enough to prevent frost from getting underneath.

Grade beams come to mind.

Hopefully this will help some, from the 2006 IBC Commentary, Section 1805.2.1 (Frost Protection): "...A common method of accomplishing this is my placing the footing bottom below the frost line." (P 18-12)

jar546
January 26th, 2012, 15:06
Some foundation walls don't even need footings. Piers don't have footings. The point is, the bottom of the built system should be low enough to prevent frost from getting underneath.

Yes, Foundation walls without footings must be below the frost depth, the code specifically says that piers must extend below the frost depth.

The point is that the language of the code requires that foundation walls extend below the frost depth. So when you have a footer, the top of it must be below frost depth.

It does not matter what is "customary" in your area if you have adopted the codebook as written. It says what it says.

Pcinspector1
January 26th, 2012, 15:09
Here the frost line depth is set at 24",(meaning thats a safe depth before frost becomes an issue). So when asked by Mr. contractor; "How deep do the footings have to be"? They are not talking about the walls, they want to know how deep to make their trench to the bottom of the trench.

12" high footing (table R403.1) + a 24" frost depth requirement (established by code and approved by ordinance) = a 36" deep trench, this is the contractors answer.

We have a general rule in our area if your live near US36 Highway, your frost depth is 36" which works out so far. Most spread footings here are 8" thick and 12" wide.

pc1

Papio Bldg Dept
January 26th, 2012, 15:24
It does not matter what is "customary" in your area if you have adopted the codebook as written. It says what it says.

In your experience, is frost protection a bearing issue? In my limited experience, a foundation wall bearing on a footing, the bottom of which is below the frost line, is not at risk of heaving...unless there are significant climate changes due in the near future. The code also says that foundations shall be built on undisturbed, compacted fill material or CLSM. It doesn't say they can be built on footings. ;)

In addition, the Figure 1805.4.6 of the 2006 IBC indicates the bottom of footing below the frost line, not the top of footing, or bottom of foundation.

Papio Bldg Dept
January 26th, 2012, 15:27
For IRC reference, please refer to Figure R403.3.1(3) in the 2006 edition.

gbhammer
January 26th, 2012, 15:30
Got to go with Papio on this one, even though he is being self depreciating with the whole limited experience stuff. The footing is apart of a load bearing system and so long as it is below the frost depth all is well.

jar546
January 26th, 2012, 15:35
It specifically states that foundation walls must extend below the frost depth. There is a foundation wall and most times, there is a footer. If it says the foundation wall must extend below the frost depth then the top of the footer must be below it too.

jar546
January 26th, 2012, 15:36
They need to change the verbiage of the code then....................

Papio Bldg Dept
January 26th, 2012, 15:38
They need to change the verbiage of the code then....................

I couldn't agree more. I will write the code change and you submit it(insert smiley faced emoticon with arrow sign denoting "I AGREE")!

jar546
January 26th, 2012, 15:40
The reason it needs to be changed is that the written code requires the foundation wall AND other..... to be below frost depth.

jj1289
January 26th, 2012, 15:47
The code also says other permanent supports. The footing is a permanent support.

imhotep
January 26th, 2012, 15:52
It specifically states that foundation walls must extend below the frost depth. There is a foundation wall and most times, there is a footer. If it says the foundation wall must extend below the frost depth then the top of the footer must be below it too.

Isn't a footing (if present) the permanent support for a foundation wall?

jar546
January 26th, 2012, 15:53
The code also says other permanent supports. The footing is a permanent support.

Yes, and it should extend below the frost depth just like the foundation wall has to. BUT, in order for the foundation wall to extend below the frost depth, the entire footer must be below it too.

jar546
January 26th, 2012, 15:54
Isn't a footing (if present) the permanent support for a foundation wall?

Yes, the code says that the foundation wall AND permanent supports must extend below the frost depth. I do not see the word OR in that sentence.

north star
January 26th, 2012, 16:06
= =


"They need to change the verbiage of the code then.................. "It would probably be easier and faster to amend your own AHJ's requirements, rather
than go through "The Cow'" CMP's.

= =

jar546
January 26th, 2012, 16:10
No, state code here, we cannot make it less restrictive

Pcinspector1
January 26th, 2012, 16:18
1997 UBC, SECTION 1806.1 sez the same thing, foundations shall extend below the frost line. All these basements in the mid-west, not built to code!

Wonder how you meet the siding requirement of 6" from earth when the foundation is to be below frost depth?

pc1

codeworks
January 26th, 2012, 17:21
it makes sense to me to go below the frost line, especially if heaving due to frost action is of concern. given that ,i'd be inclined to set the top of the footing at 36", that way the footing is in fact below the frost line. i'm from up north where the frost will go 5 feet on a cold winter, so most of the stuff i've seen was 7 feet to top of the footing, with a full 8 foot wall on it. lots-o concrete! and steel, and cold fingers and feet, and well you get the idea.

codeworks
January 26th, 2012, 17:30
to pc1 what? the 6 inches from earth is the closest the siding can be, most time any fouindation i've worked on extended from the top of the footing (whcih was built to be below frost line) to at least 8 inches above finish grade. once plates are set and framing starts, you are looking at probably seven inches from bottom of siding to earth.....plywood sheathuinfg will hang over plate and fdn at leat 3/4 of an inch.....

Pcinspector1
January 27th, 2012, 09:59
codeworks, I understand the building practice you have posted. The word in question is "FOUNDATION". The foundation must be below the frost line, let's say 24". At what point does the foundation below a frost line change to allow a wall design that you indicte to be built. On a basement foundation wall below a frost line at some point extends past the frost line to daylight for you to install a floor and wood wall as you have dipicted?

Foundation verbage change needed or a better explaination.

pc1

mtlogcabin
January 27th, 2012, 10:00
The foundation wall when bearing on a concrete footing is a system that would include the footing as part of the wall and the frost depth would be the bottom of the footing.
A crushed stone footing supporting a pre-cast foundation wall or a wood foundation wall would not be included as part of the wall sytem and therefore the frost depth would be measured to the bottom of the foundation pre-cast concrete or wood foundation wall.
FIGURE R403.1(2)
FIGURE R403.1(3)
TABLE R403.4
MINIMUM DEPTH OF CRUSHED STONE FOOTINGS (D), (inches)

Paul Sweet
January 27th, 2012, 12:48
That's odd, IBC 1809.5 says foundations, not foundation walls. Why would a residence need deeper footings than a heavier commercial building?

codeworks
January 27th, 2012, 12:49
wording needs correction. poor choice of words

Yankee
January 27th, 2012, 13:24
This is a good example of why it is helpful to know the intent of the code. Being stuck on the word "foundation" as opposed to understanding the guiding principle of the requirement

NH09
January 27th, 2012, 15:55
I have always assumed that the base of the footing (or pier) was required to be below the frost line. Although, after reading the code section I can understand why it could be interpreted as the base of the wall - It looks like a clarification is needed from ICC.

fatboy
January 27th, 2012, 16:45
As R403.1.4 speaks to minimum footing depth , and the subsection R403.1.4.1 speaks to frost protection, it is my thinking that the subsection is describing requirements for the main section. Measured to the bottom of the footing. JMHO

jar546
January 27th, 2012, 17:06
codeworks, I understand the building practice you have posted. The word in question is "FOUNDATION". The foundation must be below the frost line, let's say 24". At what point does the foundation below a frost line change to allow a wall design that you indicte to be built. On a basement foundation wall below a frost line at some point extends past the frost line to daylight for you to install a floor and wood wall as you have dipicted?

Foundation verbage change needed or a better explaination.

pc1

NO, the foundation wall must extend below the frost depth. Does not mean the entire wall, just that it must extend below the frost depth.

jar546
January 27th, 2012, 17:08
This is a good example of why it is helpful to know the intent of the code. Being stuck on the word "foundation" as opposed to understanding the guiding principle of the requirement

There is a difference between Foundation and Foundation Wall. It specifically says that the Foundation Wall must extend below the frost depth. The Foundation Wall sits on top of the Footer.

I can't believe many of you have not been enforcing this properly. If you adopted the code as written that is. ;)

Pcinspector1
January 27th, 2012, 17:41
I think the intent is the BOTTOM of the FOUNDATION WALL be below the frost footer. We have a 24" frost line, piers and trenches here are 36" deep, I think I'm enforing this properly.

Take a spead footer that is below the frost line, the bottom of the wall needs to be below the frost line as well to prevent the wall from heaving if frost penatrates between the top of the footer and the bottom of the foundation wall. Agreed

But does it say that? It sez foundations shall extend below the frost line, dose'nt say the bottom of the foundation wall?

Verbage changed needed IMO.

pc1

mn joe
January 27th, 2012, 17:58
Jar, that's a cheap shot. I expected better from you. I consider the walls and the footings to be part of a foundation wall system. You take the wording of "foundation wall" more literally. That is an administrative call that any B.O. is entitled to make. My interpretation is no more right or wrong than yours. I enforce the code properly according to the way I read it, as do you.

Joe

jar546
January 27th, 2012, 18:00
It says the foundation wall must extend below the frost depth, not just foundation. BTW, there is a difference.

There is a forest through those trees

jar546
January 27th, 2012, 18:03
Jar, that's a cheap shot. I expected better from you. I consider the walls and the footings to be part of a foundation wall system. You take the wording of "foundation wall" more literally. That is an administrative call that any B.O. is entitled to make. My interpretation is no more right or wrong than yours. I enforce the code properly according to the way I read it, as do you.

Joe

I don't agree with your cheap shot opinion but it is your opinion and you are entitled to it. Nothing says foundation wall system, it says foundation wall. There are footers and there are walls.

Did you ever see a block wall get pushed off of a footer in a crawlspace? I did, multiple times. Common problem? Shallow frost footer and wall not below frost depth.

Architect1281
January 28th, 2012, 09:23
Jar in the older guys days when were ere on earlier CABO ther was language that would actually allow the grushed gravel - 3/4 to 1-1/2" stone leveling -drainage pad to be counted up to a max of 12" depth as contributing to the "depth to frost protection" IF the soil below was free draining (non -expansive) I as a designer and a CBO absolutly count the Footing as a foundation - WHY? Cause I just prepared submitted and had approved a V/Coastal A pier and grade beam building support system where the Footing is at 7 foot depth (due to scour and erosion potential) the Piers are at 6 foot depth (to top of footing) and the grade beams are only 16" to the base (between and to top of piers) with a "Frost Depth" of 48" the grade beams are to controlled fill free draining material - the slab which abuts per asce-24 and Fema guides is designed to break up - so I would absolutly be confident that the "Frost Depth you are discussing is to the Lowest Level of structural support. Problems with ICC code language is PEOPLE OVER THINK and then others attemp to define what they are supposed to think, and attempt to write language to make it crystal clear and cover every possible nuance. Proble = People Thinking

Architect1281
January 28th, 2012, 09:25
DId I tell you I Touch type and miss the edit button so to Harvey Schorr sorry for the TYPOZ - Harvey was a BIG (his opinion) architect at one of the mega firms I worked at - Fancied himself an English Lit professor / architect.

Inspector Gift
January 28th, 2012, 14:31
It does not matter what is "customary" in your area if you have adopted the codebook as written. It says what it says.

While I agree that our codes can use improvements, the word "FOOTER" is not used in any of the codes I have. Which code section is it used in your codes, Jeff?

It always puzzles me when builders or inspectors use incorrect terminology, and yet claim they know the code. So, with all due respect, I humbly suggest that they clarify and check their own verbiage before criticizing the model code. Perhaps the word "FOOTER" is the same as "FOOTING" and still part of the foundation system?

Is not the "foundation wall" a system? Does it include reinforcement steel, anchor and holdown bolts, a minimum thickness, and a footing (or point of bearing)? Does a monolithic slab have a footing (or point of bearing)? -- I'd say 'YES" to all three questions!

The answers to my questions often become apparent when I strive to understand the INTENT and PURPOSE of a code section.

Yankee
January 28th, 2012, 21:14
Think of the big picture, the AHJ sets the frost depth. Set it at the appropriate distance to allow for measuring to the bottom of the footing. That removes all the high-jinx with footing depths etc etc.

fatboy
January 29th, 2012, 00:35
Excellent point, the AHJ will decide what the minimum depth is to the bottom of the footing...........

Keystone
January 29th, 2012, 07:01
Not to go off in another direction but "Inspector Gift" hit on one of my pet peeves, terminology - footer & masonary - footing & masonry

jar546
January 29th, 2012, 08:06
While I agree that our codes can use improvements, the word "FOOTER" is not used in any of the codes I have. Which code section is it used in your codes, Jeff?

It always puzzles me when builders or inspectors use incorrect terminology, and yet claim they know the code. So, with all due respect, I humbly suggest that they clarify and check their own verbiage before criticizing the model code. Perhaps the word "FOOTER" is the same as "FOOTING" and still part of the foundation system?

Is not the "foundation wall" a system? Does it include reinforcement steel, anchor and holdown bolts, a minimum thickness, and a footing (or point of bearing)? Does a monolithic slab have a footing (or point of bearing)? -- I'd say 'YES" to all three questions!

The answers to my questions often become apparent when I strive to understand the INTENT and PURPOSE of a code section.

OK, you don't like the word footer, you would prefer footing. No problem, that is the way it is written. I will give you that because if I am being technical then I am wrong and should use the proper terminology. Thank you for bringing that to my attention.

That still does not, however take away from the fact that a footing is a footing and a foundation wall is a wall. Why then are footings under section 403 and foundation walls are under 404? They are integral to each other but still are clarified separately in the code and by construction.

A footing is the system in which the foundation sits on. It is the base. We rarely see monolithic pours and we do a footing inspection.

Afterwards, the foundation wall is constructed since the separate footing already was.

Together, however both the footing and the foundation wall are considered the foundation. A foundation includes both, but a foundation wall is only part of it, just like the separate footing is.

That is why the word "wall" is after the word foundation. It is a separate structure, most of the time constructed with a different material than the wall itself.

Therefore, it is our belief and has been since some of our municipalities had the BOCA standard that the foundation wall is a separately built structure and that structure must extend below the frost depth. There are footings, there are foundation walls and there is a foundation which is a combination of the two.

jar546
January 29th, 2012, 08:14
Not to go off in another direction but "Inspector Gift" hit on one of my pet peeves, terminology - footer & masonary - footing & masonry

I have a similar one since 80% of the electricians and inspectors don't know how to spell "receptacle". Instead we get: recepticle most of the time and other variations such as resepticle, raceptacle, and so on.........

Kind of like when I point to a ceiling light box or smoke detector box and refer to it as an outlet. They look at me cross-eyed because they don't know the difference between an outlet and a receptacle.

DRP
January 29th, 2012, 09:04
Hmmm, are you measuring from the required minimum footing depth or from the as built footing depth? For speed and convenience I have simply poured the footing trench full to grade a time or two. On two that spring to mind, from there we built rubblestone walls, nothing was "slippery" to frost.

imhotep
January 29th, 2012, 10:52
Therefore, it is our belief and has been since some of our municipalities had the BOCA standard that the foundation wall is a separately built structure and that structure must extend below the frost depth. There are footings, there are foundation walls and there is a foundation which is a combination of the two.

So why not take a position that in addition to foundation walls "other permanent supports of buildings and structures" such as beams, girders, and posts be located below the frost depth as well? That would be consistent with the position that the top of spread footings shall be located at or below the frost line to allow for the bottom of the concrete, CMU or PT wood foundation wall to extend below the frost depth.

incognito
January 30th, 2012, 00:01
There is no logical reason to extend the foundation wall below the frost line. Even if that is someones interpretation of the code it is ridiculous and probably(and rightfully) the quickest way to the unemployment line.

Mark K
January 30th, 2012, 02:07
Agree with incognito on the first point but the reality is that wrong interpretations do not typically appear to have any consequences for the individual making them.

jar546
January 30th, 2012, 07:25
If the code stated clearly that the foundation had to extend below the frost line, I could understand. It does, however, clearly state that the "foundation wall" which is part of the foundation assembly must extend below the frost depth. It is physically impossible for the "foundation wall" to extend below the frost depth unless the entire footing is below frost depth. You see, that is how it is written. There is no gray area, the code specifies "foundation wall", not just foundation or footing. There is a reason behind it. I have contacted multiple inspectors about this privately and they all have the same opinion. I don't see how you can read those written words in the codebook and not come to the same conclusion.

rshuey
January 30th, 2012, 08:02
I agree jar. We set our frost depth at 48" to handle this problem.

imhotep
January 30th, 2012, 09:28
If the code stated clearly that the foundation had to extend below the frost line, I could understand. It does, however, clearly state that the "foundation wall" which is part of the foundation assembly must extend below the frost depth. It is physically impossible for the "foundation wall" to extend below the frost depth unless the entire footing is below frost depth. You see, that is how it is written. There is no gray area, the code specifies "foundation wall", not just foundation or footing. There is a reason behind it. I have contacted multiple inspectors about this privately and they all have the same opinion. I don't see how you can read those written words in the codebook and not come to the same conclusion.

So how do you reconcile the IBC's provision?


2009 IBC
1809.5 Frost protection. Except where otherwise protected from frost, foundations and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:

In an inverted T footing the foundation wall distributes its load through by spreading out into a strip footing. In essence the "foundation wall" does not mysteriously end at the top of the footing, but rather the wall continues through the expanded width of the footing. The issue is ground heave due to moisture laden soils freezing.

TJacobs
January 30th, 2012, 09:49
2006 IRC, Table R301.2(1), Frost line depth, Footnote b: The frost line depth may require deeper footings than indicated in Figure R403.1(1). The jurisdiction shall fill in the frost line depth column with the minimum depth of footing below finish grade.

A trench foundation has a built-in footing. Would you require a spread footing to bear lower than a trench? Isn't the 42-inch frost depth (here) the minimum bearing level of the entire foundation system?

Papio Bldg Dept
January 30th, 2012, 10:16
Jar, you never responded to my post about diagrams R403.1(2) & R403.1(3) where the frost depth is shown at the bottom of the crushed stone layer, which is a minimum of six inches below the footer plate? This would seem to cement, if not set in stone, your argument, that the frost line be below the footing. ;)

High Desert
January 30th, 2012, 11:52
Jar, you need to read and apply the entire section of that code provision. The charging statement is minimum depth for footings. The last sentence says the depths of footing where applicable, shall also conform to Sections R403.1.4.1 though R403.1.4.2. One of the methods is to place the footing below the frost depth, which the statement in R403.1.4 tells you you must do.The section you are hung up on says you need to protect foundation walls, piers and other permanent supports of buildings and structures from frost by one or more of the following methods. So in other words, if you place the footing below the frost depth, the code is saying that is one way to protect the foundation walls. You are reading way too much into the code.

R403.1.4 Minimum depth. All exterior footings shall be
placed at least 12 inches (305 mm) below the undisturbed
ground surface. Where applicable, the depth of footings shall
also conform to Sections R403.1.4.1 through R403.1.4.2.

R403.1.4.1 Frost protection. Except where otherwise
protected from frost, foundation walls, piers and other
permanent supports of buildings and structures shall be
protected from frost by one or more of the following methods:
1. Extended below the frost line specified in Table
R301.2.(1);
2. Constructing in accordance with Section R403.3;
3. Constructing in accordance with ASCE 32; or
4. Erected on solid rock.

gbhammer
January 30th, 2012, 13:29
Jar are you just trying to create a hot topic? :devil

mn joe
January 30th, 2012, 15:00
That was my question too, but I didn't want to slow down the thread!
Joe

jar546
January 30th, 2012, 15:09
Jar are you just trying to create a hot topic? :devil

Yes, but I have to throw myself into it.................

Great responses from many, even though many of you are wrong

gbhammer
January 30th, 2012, 15:30
Yes, but I have to throw myself into it.................

Great responses from many, even though many of you are wrong

LOL

Now please answer papio's question about the figures that show a foundation wall sitting on crushed gravel where it clearly defines the bottom of the gravel as needing to be below the frost line, not the wall but the bottom of the gravel.

The diagrams are real cut and dry, the fon

jar546
January 30th, 2012, 15:37
Jar, you never responded to my post about diagrams R403.1(2) & R403.1(3) where the frost depth is shown at the bottom of the crushed stone layer, which is a minimum of six inches below the footer plate? This would seem to cement, if not set in stone, your argument, that the frost line be below the footing. ;)

I am not familiar with wooden foundation walls without concrete footings. Looks like they made a mistake on the diagrams because it does not match the wording of the code. :)

gbhammer
January 30th, 2012, 15:44
I am not familiar with wooden foundation walls without concrete footings. Looks like they made a mistake on the diagrams because it does not match the wording of the code. :)

I am feeling a bit under the weather today so that actually hurt when I bursted out laughing about who was making the mistake.

High Desert
January 30th, 2012, 16:32
I hate to say it Jar, but you are wrong. The charging statement refers to footings placed below the frost line. Section R403.1.4.1 is a subsection of R403.1.4. Applying your logic the entire foundation wall would have to be below the frost line, which is virtually impossible.

fatboy
January 30th, 2012, 17:02
"The charging statement refers to footings placed below the frost line. Section R403.1.4.1 is a subsection of R403.1.4."

As I said in post #37...........

Mule
January 30th, 2012, 17:03
Why can't the wall be part of the footing? Where is it in the code that the wall has to be poured in one continuous pour?

Figure R317.1(5) shows that the foundation wall is part of the footing.

Papio Bldg Dept
January 30th, 2012, 17:04
I am feeling a bit under the weather today so that actually hurt when I bursted out laughing about who was making the mistake.

I think jar did an excellent job getting 4 pages out of this topic myself. Given that I worked on several projects with one of the ICC's consulting engineers for wood foundations, I feel fairly certain jar can only dig his footing hole deeper at this point if he still wants to come out on top.

Papio Bldg Dept
January 30th, 2012, 17:19
for kicks and giggles, here is the 2006 IBC (Commentary in italics)

1805.2 Depth of footings. The minimum depth of footings below the undisturbed ground surface shall be 12 inches. Where applicable the depth of the footings shall also conform to Sections 1805.2.1 through 1805.2.3.

*Footings are required to extend below the ground surface a minimum of 12 inches. This is considered a minimum depth to protect the footing from movement of the soil caused by freezing and thawing in mild climate areas (see Section 1805.2.1 for general frost protection requirements).

1805.2.1 Frost Protection. Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected by one or more of the following methods:

1. Extending below the frost line of the locality;
2. Constructing in accordance with ASCE 32; or
3. Erecting on solid rock.

Exceptions: Blah blah blah.

Footings shall not bear on frozen soil unless such frozen condition is of a permanent character.

*Unless the exception applies, the foundation is to be protected from frost in accordance with this Section. A common method of accomplishing this is by placing the footing bottom below the frost line.

gbhammer
January 30th, 2012, 17:24
You know we had 160 responses to the document submission thread.

jar546
January 30th, 2012, 18:02
If you have a footing, it obviously must be below frost depth. The issue is the wording of the code that specifies that the foundation wall extend below frost depth. There is a section on footings and a section on foundation walls. They are two different entities. The chapter, however is for foundations. Which is what you get when you marry the two together.

Who is up for a code change submission?

fatboy
January 30th, 2012, 18:54
I'll take a whack at it, to late to get anything into the IBC, but there's plenty of time for the IRC though, January 3, 2013. The Colorado Chapter is very active with code changes, we have a solid committee that reviews our proposals. I'll drop it in a new thread here when I have something.

Unless anyone else wants to do it?

DRP
January 30th, 2012, 19:33
And everyone takes one step back :D

jar546
January 30th, 2012, 19:50
We will have the 2009 here until at least 2015 so I don't see any reason for me to put time and effort into it. We will just keep enforcing it the way it is written without an hassles as we always have.

Mule
January 31st, 2012, 09:10
Written! :) How is it written? In my opinion I see it written as the foundation wall can be part of the footing and the bottom of the footing/wall has to be below frost line. :)

Pcinspector1
January 31st, 2012, 09:45
Jar, could you post a drawing of how it's done in PA! or your area? This has been a great topic, I might add.

pc1

Pcinspector1
January 31st, 2012, 09:57
Thoose of you that use to get the building journal and have back issues, check out the one for 2003 that has trench footings, that issue also had an article about smoke alarms for ADA requirements on the top of the magizine. I don't have the mag in the office.

pc1

High Desert
January 31st, 2012, 11:43
Jar, just curious. Suppose you have a foundation wall atop a footing. If I take your interpretation literally, the entire foundation must be below the frost line (an obvious impossibility), or do you have them set bottom of the foudation wall 1 foot, 1 inch or maybe 1/8" below the frost line? That's why the code is written the way it is. I don't see a need for a code change. The real intent of the provision is to protect the foundation wall by placing the footing below the frost line. See my Post #61.

Mule
January 31st, 2012, 11:54
Why can't thhe foundation wall be part of the footing?

http://pic20.picturetrail.com/VOL148/1822929/5439194/400786615.jpg

Papio Bldg Dept
January 31st, 2012, 13:51
Why can't thhe foundation wall be part of the footing?

http://pic20.picturetrail.com/VOL148/1822929/5439194/400786615.jpg

Ah, to be or not to be. Are footings (footers) and foundations (over-sized stem walls) mutually exclusive? If you only have a foundation (i.e., grade beam), is there no footing? If you only have a footing (i.e., thickened slab), is there no foundation? Since footing is mentioned in the text, maybe it doesn't need frost-protection. Where is Rene Magritte when you need him?

Papio Bldg Dept
January 31st, 2012, 13:52
(Edited for typo in bold caps) Ah, to be or not to be. Are footings (footers) and foundations (over-sized stem walls) mutually exclusive? If you only have a foundation (i.e., grade beam), is there no footing? If you only have a footing (i.e., thickened slab), is there no foundation? Since footing is NOTmentioned in the text, maybe it doesn't need frost-protection. Where is Rene Magritte when you need him?

GBrackins
January 31st, 2012, 18:47
Correct me if I am wrong (as if there was no chance of that here ...) but when I read Table R301.2(1) for Frost Line Depth it doesn't it say it subpart b "The jurisdiction shall fill in the frost line depth column with the minimum depth of footing below finish grade?" Doesn't this specify the depth of footing, or am I reading this incorrectly?

High Desert
January 31st, 2012, 19:18
GBrackins, you are reading it correctly. It's the footing frost depth.

Papio Bldg Dept
February 1st, 2012, 09:15
Correct me if I am wrong (as if there was no chance of that here ...) but when I read Table R301.2(1) for Frost Line Depth it doesn't it say it subpart b "The jurisdiction shall fill in the frost line depth column with the minimum depth of footing below finish grade?" Doesn't this specify the depth of footing, or am I reading this incorrectly?

Winner! Nice job GBrackins, now let's see what jar bounces back with. ;)

Pcinspector1
February 1st, 2012, 09:26
GBrankins, that's how I take it also.

pc1

Mac
February 1st, 2012, 10:30
Not to distract here, but figure R403.1.(1) does show a wall bearing directly on soil.

High Desert
February 1st, 2012, 11:22
Mac, in that case the bottom of the wall would be the footing. Using jar's logic that entire wall would have to be below the frost line. Tough to build something on it when it's underground. I've only seen that type of construction done once in my 27 years of inspections. The wall would have to meet the width requirements for footings in Table R403.1 I believe.

jar546
February 1st, 2012, 11:26
Why can't thhe foundation wall be part of the footing?




That is a partial drawing. Look at the bottom of the wall, it continues

jar546
February 1st, 2012, 11:27
Mac, in that case the bottom of the wall would be the footing. Using jar's logic that entire wall would have to be below the frost line. Tough to build something on it when it's underground. I've only seen that type of construction done once in my 27 years of inspections. The wall would have to meet the width requirements for footings in Table R403.1 I believe.

Must EXTEND below the frost depth. Nothing says it has to be completely below frost depth.

gbhammer
February 1st, 2012, 11:37
Well look at that, good job GB.
It is amazing what you find when you read the book.

Pcinspector1
February 1st, 2012, 12:28
Theres two gb's?

Does a concrete bunker meet the foundation wall requirement of being below the frost line? ;)

pc1

GBrackins
February 1st, 2012, 12:44
jar ...

Correct me if I am wrong, but when I read Table R301.2(1) for Frost Line Depth doesn't it say in subpart b "The jurisdiction shall fill in the frost line depth column with the minimum depth of footing below finish grade?" Doesn't this specify the depth of footing, or am I reading this incorrectly? If this is correct, and the local jurisdiction specifies the depth of footing (not foundation wall) how can the foundation wall be below the footing?

I understand where you are coming from, but don't you have to use the whole and not just a part of the code? I agree section R403.1.4.1 needs to be reworded so that we don't have incorrect interpretations.

steveray
February 1st, 2012, 12:52
Actually the IRC does not allow for the straight wall to be the footing as it needs min 2" projections.....I have no heartburn with it actually working that way, but the prescriptive codesays.....
R403.1.1 Minimum size.

Minimum sizes for concrete and masonry footings shall be as set forth in Table R403.1 and Figure R403.1(1). The footing width, W, shall be based on the load-bearing value of the soil in accordance with Table R401.4.1. Spread footings shall be at least 6 inches (152 mm) in thickness. Footing projections, P, shall be at least 2 inches (51 mm) and shall not exceed the thickness of the footing. The size of footings supporting piers and columns shall be based on the tributary load and allowable soil pressure in accordance with Table R401.4.1. Footings for wood foundations shall be in accordance with the details set forth in Section R403.2, and Figures R403.1(2) and R403.1(3).


Mac, in that case the bottom of the wall would be the footing. Using jar's logic that entire wall would have to be below the frost line. Tough to build something on it when it's underground. I've only seen that type of construction done once in my 27 years of inspections. The wall would have to meet the width requirements for footings in Table R403.1 I believe.

High Desert
February 1st, 2012, 20:06
steveray, I did thank you for your response but why would they even have a figure for "Basement or Crawl Space with Foundation Wall Bearing Directly on Soil" if you couldn't construct it that way? You will notice that the other figures on that page specifically identify walls with spread footings with the P measurement, but the wall figure does not. I'll agree that it's not very logical, but nonetheless, it is shown that way.

Anyone have an answer on this one?

mtlogcabin
February 2nd, 2012, 10:30
Read the description under each drawing. The only one that is referencing a foundation wall is the one without a footer. The others are either a masonry or concrete basement or crawlspace wall on a spread footing.
If you want to construct a 12" to 42" wide foundation wall to bear directly on the soil I guess the code will allow it.
The IRC has a section for pre-cast foundation walls with crushed stone footers.

High Desert
February 2nd, 2012, 11:31
mtlogcabin, thank you. that's the way I also read it. Your wall would have to meet the footing width of Table R403.1.

Papio Bldg Dept
February 2nd, 2012, 11:40
If you want to construct a 12" to 42" wide foundation wall to bear directly on the soil I guess the code will allow it.


We used to do 12" wide x 42" deep grade beam (frost line at 42") for slab on grade ranches all the time....works pretty slick when you need a brick ledge too. Some might call that a footing, others might call it a foundation, it's still six one way, and half a dozen the other.

Papio Bldg Dept
February 2nd, 2012, 11:42
mtlogcabin, thank you. that's the way I also read it. Your wall would have to meet the footing width of Table R403.1.

The only place we allow less than 12 inches is in on frost protected stoops.

steveray
February 2nd, 2012, 12:41
The only place I have seen a wall w/o footings is Superior Walls precast, but they are engineered anyway, so I have not had to make the call on the illogical code contrdiction....yet....

Paul Sweet
February 3rd, 2012, 12:58
A century ago it was common to excavate down to the frost line and build stone or brick foundation walls right on the subsoil. Stone foundations were typically 16" or thicker, so they didn't have projections at the botton. Brick walls would typically have a few courses corbeled out another wythe or two. The verbiage for the foundation wall to extend below the frost line is probably based on this archaic construction method.

gbhammer
February 3rd, 2012, 13:34
It only took one hundred responses to go medieval on the thread. Gotta love this forum.