# Thread: Help on ICC practice Exam Question

1. ## Help on ICC practice Exam Question

Last edited by RobertSmith; 03-01-2008 at 08:26 PM.

2. ## Re: Help on ICC practice Exam Question

Robert, you have to interpolate to get the answer.

You are given a height of 9' and an unbalanced backfill height of 7'-6". In the column with the heading SC,MH,ML-CL and inorganic CL it give a minimum wall thickness of 10" at 7' and 12" at 8'. Since you are dealing with 7'-6" you need to add 1" to 10". Of course this gives you 11". But none of the answers are 11". Remember 11" is the minimum. As such, you have to choose the answer > than 11", or 11-1/2" to be exact.

3. ## Re: Help on ICC practice Exam Question

(bold and underlining are mine)
Originally Posted by RobertSmith
16. A plain concrete foundation wall ...

The answer comes from the 2006 IRC Section: Tables R404.1.1(1)
Look at the heading of that table ( TABLE R404.1.1(1), PLAIN MASONRY FOUNDATION WALLS ), then go to the correct table ( TABLE R404.1.1(5), CONCRETE FOUNDATION WALLS h, i, j, k ).

4. ## Re: Help on ICC practice Exam Question

I was using the 2003 IRC. It doesnt have table 404.1.1(5). Table 404.1.1(1) is what Robert references which in the 2003 code does apply to plain concrete.
I assume he is given that reference (404.1.1(1) from his study book. Maybe his study book was using the older version of IRC.

5. ## Re: Help on ICC practice Exam Question

Originally Posted by imported_John Smith
I was using the 2003 IRC. It doesnt have table 404.1.1(5). Table 404.1.1(1) is what Robert references which in the 2003 code does apply to plain concrete.
I see, I just went and checked the 2003 IRC and both tables are combined into one in table back then.

However ... ... he also stated (bold is mine) "The answer comes from the 2006 IRC Section: Tables R404.1.1(1)".

Thus (I am guessing) the practice test updated everything EXCEPT for the table number in the answer.

6. ## Re: Help on ICC practice Exam Question

As others pointed out there were significant changes in section 404 of the IRC from 2003 to 2006.

In 2003, the correct table to use for answering the question is Table R404.1.1(1), and the procedure to get the answer is how John has posted.

In 2006, the correct table to use is Table R404.1.1(5) as Jerry has posted. The correct answer for plain concrete is still 11.5 inches, but getting there is not as straightforward as it was under the 2003 code.

Using Table R404.1.1(5) and the information given in the question, you would enter the table using 9 feet in column one (wall height), then read across the 7 and 8 feet rows in column 2 (maximum height of unbalanced fill), until you get get to the sets of columns under the SC soil type (clayey sand). You'll note in the table that the only place that plain concrete ("PC") shows up on either of those two rows under the SC soil type is at a minimum thickness of 11.5 inches when the unbalanced fill is at a maximum height of 7 feet. Your unbalanced fill is 7'-6", so you drop down to the 8 feet row and you see that all of the wall thicknesses require reinforced concrete instead of plain concrete, except that there's a footnote h next to the entry in the 11.5 inch column ... and when you read footnote h it says that you can use plain concrete if you also specify a minimum compressive strength of 3,500 psi. If psi for concrete is not specified (as was the case in the original question) then a normal strength of 2,500 psi is assumed.

The correct answer to that question under the 2006 code is a minimum thickness of 11.5 inches with a minimum compressive strength of 3,500 psi. But of the four answers given, D) is the most correct.

The procedure to arrive at the correct answer using the 2006 code and the question data, and the 2003 table reference, leads me to believe that the question was not updated for the 2006 code but was carried over from 2003.

7. ## Re: Help on ICC practice Exam Question

This is the way I got to 11.5 inches in the 2006 IRC.

Table R405.1, Properties of Soils Classified According to the Unified Soil Classification System, SM is Silty sand, sand-silt mixtures, and SC is Clayey sands, sand-clay mixture. The question specified that clayey sand soil was present. Clayey sand is SC soil.

Table R404.1.1(5), Concrete Foundation Walls, lists SC soil listed in two columns: 1) in the GM, GC, SM, SM-SC and ML column; 2) and in the SC, ML-CL and inorganic CL column. At a foundation wall height of 9 feet, the the SC, ML-CL and inorganic CL column stops PC (Plain Concrete) at 7 feet maximum unbalanced fill. The question, however, specified 7 feet 6 inches, which exceeds the maximum height for that that soil type column. Going over to the GM, GC, SM, SM-SC and ML column, for a 9 foot high foundation wall, an unbalanced fill height of up to 8 feet is allowed with an 11.5 inch thick wall.

The answer is still D, but for a different reason.

8. ## Re: Help on ICC practice Exam Question

Jerry,

SC and SM-SC are not the same. The question specifies "clayey sand" which is SC. SM-SC is a sand-silt-clay mix, which is known as a "borderline soil" or a "boundary classification" -- these are soils that have properties that do not slot them into the standard classifications and they are labeled with the two names that they most closely resemble. ML-CL is another one. Table R405.1 does not show the borderline soils. For this question in Table R404.1.1(5) you need to use the columns under SC with design lateral soil loads of 60 psf per foot of depth.

Brandon

Last edited by Brandon Chew; 01-19-2008 at 10:35 PM. Reason: spelling

9. ## Re: Help on ICC practice Exam Question

Originally Posted by Brandon Chew
SC and SM-SC are not the same. The question specifies "clayey sand" which is SC. SM-SC is a sand-silt-clay mix, which is known as a "borderline soil" or a "boundary classification" -- these are soils that have properties that do not slot them into the standard classifications and they are labeled with the two names that they most closely resemble. ML-CL is another one.
I thought that was not a "mix" but where the two soil types meet in changing from one to the other (which I guess would be a "mix"), and, as thus with two separate soil types on one location.

Table R405.1 does not show the borderline soils. For this question in Table R404.1.1(5) you need to use the columns under SC with design lateral soil loads of 60 psf per foot of depth.
And Table R404.1.1(5), under soil type SC, the unbalanced height allowed for an 11.5" stops at 7 feet for a wall height of 9 feet.

Thus, under SC soil type, there is no listing for plain concrete at 7' 6" unbalance soil height with a wall height of 9 feet.

After all of that, then, what is the answer ... being as you cannot go past 7 feet unbalanced fill height for a 9 foot high foundation wall?

*IF* the foundation wall were only 8 feet high, then you could go to an unbalanced fill height of 8 feet, but not over 7 feet for a 9 foot high wall.

What am I missing????

Last edited by Jerry Peck; 01-20-2008 at 02:17 PM. Reason: edited "(" ")" for errant quote to "[" "]"

10. ## Re: Help on ICC practice Exam Question

Originally Posted by Jerry Peck
I thought that was not a "mix" but where the two soil types meet in changing from one to the other (which I guess would be a "mix"), and, as thus with two separate soil types on one location.
SM-SC is one label for a specific type of soil. SM is a sandy soil where the predominate fraction of the fines are silt. SC is a sandy soil where the predominate fraction of the fines are clay. SM-SC is a sandy soil where the fines have a lot of silt AND clay. It's a unique soil type with engineering properties all it's own. It is labeled with the hyphen and the two soil types that it most closely resembles, thus the use of the terms "boundary or borderline" to describe these soils. It's a quirk of the USCS testing process that when you start with a soil sample and analyze it, you don't always wind up in one of the categories that is listed in Table R405.1. In the case of the SM-SC soil, when you run the plasticity test the result falls into the hatched zone on the plasticity chart, meaning there is both silt and clay present, but neither dominates the other.

Originally Posted by Jerry Peck
And Table R404.1.1(5), under soil type SC, the unbalanced height allowed for an 11.5" stops at 7 feet for a wall height of 9 feet.
Nope. It goes up to nine feet. It just changes from plain concrete at 2500 psi, to higher strength concrete, to adding rebar.

Originally Posted by Jerry Peck
Thus, under SC soil type, there is no listing for plain concrete at 7' 6" unbalance soil height with a wall height of 9 feet.
True. You need to drop down to the row for 8 feet max unbalanced fill height.

Originally Posted by Jerry Peck
After all of that, then, what is the answer ... being as you cannot go past 7 feet unbalanced fill height for a 9 foot high foundation wall?

*IF* the foundation wall were only 8 feet high, then you could go to an unbalanced fill height of 8 feet, but not over 7 feet for a 9 foot high wall.

What am I missing????
You are missing footnote h, from my post above:

Your unbalanced fill is 7'-6", so you drop down to the 8 feet row and you see that all of the wall thicknesses require reinforced concrete instead of plain concrete, except that there's a footnote h next to the entry in the 11.5 inch column ... and when you read footnote h it says that you can use plain concrete if you also specify a minimum compressive strength of 3,500 psi.

Brandon

11. ## Re: Help on ICC practice Exam Question

Originally Posted by RobertSmith
Well, I'm glad I'm not the only ones confused by this question!!!!

Could we define:

SC =?
GM =?
GC = ?
SM-SC = ?
ML =?

I looked in the 2006 IRC and could not find where these soil types abbreviations are defined.

Thanks for everyones help
Robert,

See Table R405.1 in the 2006 IRC. I don't think the SM-SC or the ML-CL soils are defined in the code book. The way this would work in real life is that you would have a soil report that would tell you what kind of soils you are dealing with on the site, then you select the columns in Table R404.1.1(5) that correspond to those soil types.

Brandon

12. ## Re: Help on ICC practice Exam Question

Originally Posted by Jerry Peck
And Table R404.1.1(5), under soil type SC, the unbalanced height allowed for an 11.5" stops at 7 feet for a wall height of 9 feet.
Originally Posted by Brandon Chew
Nope. It goes up to nine feet. It just changes from plain concrete at 2500 psi, to higher strength concrete, to adding rebar.
Yes, but you are no longer in plain concrete, which is what the question was.

That means, as I said, it (plain concrete) "And Table R404.1.1(5), under soil type SC, the unbalanced height allowed for an 11.5" stops at 7 feet for a wall height of 9 feet." Plain concrete, which is specified in the question, does not go beyond 7 feet.

Jerry said: "Thus, under SC soil type, there is no listing for plain concrete at 7' 6" unbalance soil height with a wall height of 9 feet."
Brandon said: "True. You need to drop down to the row for 8 feet max unbalanced fill height."

However, "Plain Concrete" (as stated in the question) stops at 7 feet maximum, so you cannot drop down to the 8 feet row.

Jerry said: "What am I missing????"
Brandon said: "You are missing footnote h, from my post above:"

No, I read that note, and that note says:
"h. A plain concrete wall with a minimum thickness of 11.5 inches is permitted, provided minimum specified compressive strength of concrete, f c , is 3,500 psi." And, note 'h' is applicable to the entire table as it is shown at the top of the table at the heading.

By the way, note 'h', applying to the entire table, does it only apply to all the 11.5 inch columns, to all columns, or to only one row in particular (in which case why is it a sub note to the entire table)?

Perhaps you could clue me in on why they have sub note 'h' at the table heading instead of at individual locations?

Last edited by Jerry Peck; 01-20-2008 at 02:28 PM.

13. ## Re: Help on ICC practice Exam Question

Originally Posted by Jerry Peck
"h. A plain concrete wall with a minimum thickness of 11.5 inches is permitted, provided minimum specified compressive strength of concrete, f c , is 3,500 psi." And, note 'h' is applicable to the entire table as it is shown at the top of the table at the heading.

By the way, note 'h', applying to the entire table, does it only apply to all the 11.5 inch columns, to all columns, or to only one row in particular (in which case why is it a sub note to the entire table)?

Perhaps you could clue me in on why they have sub note 'h' at the table heading instead of at individual locations?
I don't know why they put the h up at the Table heading -- it seems likely to confuse people with them having it up there. They did put footnote h at the individual locations at which it applies. See:
• The #4 rebar @ 48" entry on the row for a 9 foot wall height & 8 feet unbalanced backfill (which is the answer to this question)
• The #6 rebar @ 45" entry on the row for a 10 foot wall height & 8 feet unbalanced backfill
• The #4 rebar @ 48" entry on the row for a 10 foot wall height & 9 feet unbalanced backfill
In those three specific instances, you can build an 11.5 inch thick plain concrete wall if you specify concrete with a minimum compressive strength of 3500 psi, or you can build reinforced concrete walls at that thickness with normal strength concrete at 2500 psi.

14. ## Re: Help on ICC practice Exam Question

Originally Posted by Brandon Chew
I don't know why they put the h up at the Table heading -- it seems likely to confuse people with them having it up there. They did put footnote h at the individual locations at which it applies. See:
• The #4 rebar @ 48" entry on the row for a 9 foot wall height & 8 feet unbalanced backfill (which is the answer to this question)
No, again, the question was:

Originally Posted by RobertSmith
16. A plain concrete foundation wall ...
Brandon, keep thinking "Plain Concrete", that is the question.

Okay, now ... for PLAIN CONCRETE ... what is the answer and why?

There is no foot note 'h' at plain concrete at a 9 foot wall with 7 or 8 feet unbalanced fill.

There is at 8 feet unbalance fill with rebar, with note 'h' stating that you could use plain concrete there if it is 3,500 psi, but the question did not stated the at 3,500 psi.

Footnote i states "i. Concrete shall have a specified compressive strength of not less than 2,500 psi at 28 days, unless a higher strength is required by note g or h.".

Are you basing your answer on the fact that the question does not specify the psi of the concrete, thus you can use 3,500 psi?

If so, then I would have to agree with you, but I did not take that as what the question was asking. Maybe I should have?

And, I have to admit (and already did) that the footnote 'h' at the heading screwed it all up for me.

15. ## Re: Help on ICC practice Exam Question

Originally Posted by Jerry Peck
No, again, the question was:

16. A plain concrete foundation wall ...

Brandon, keep thinking "Plain Concrete", that is the question.

Okay, now ... for PLAIN CONCRETE ... what is the answer and why?
From my first post in this thread, the answer for PLAIN CONCRETE is a minimum thickness of 11.5 inches using concrete with a minimum compressive strength of 3,500 psi.

Given:
• plain concrete foundation wall
• 9 feet tall
• unbalanced fill height 7'-6''
• clayey sand soil
• assume Seismic Design Category C
Find: minimum allowable thickness of the foundation wall in accordance with the code’s prescriptive requirements.

Under the 2003 IRC, use Table 404.1.1(1) and the procedure posted by John Smith in this thread to arrive at answer D which is 11.5 inches.

Under the 2006 IRC ......
1. R404.1.2 requires you to use Table 404.1.1(5) and comply with R402.2.
2. Using Table 404.1.1(5), in column 1, choose 9 feet for maximum wall height.
3. In column 2, choose 8 feet for maximum unbalanced fill height.
4. Read footnote a, which refers you to Table R405.1.
5. Go to Table R405.1. Scan down the descriptions in column 3 until you find "clayey sands". Look in column 2 and find the symbol for clayey sand is SC.
6. Return to Table 404.1.1(5). Find the set of four wall thickness columns that apply to the SC soil class. They are the last four columns in the table, the ones that have the design lateral soil load of 60 psf per foot of depth.
7. Reading across the row that has 9 in column 1 and 8 in column 2 until you get to the four columns under the SC soil class, gives you four different walls:
1. 5.5 inches thick reinforced concrete using vertical #6 rebar spaced 24''
2. 7.5 inches thick reinforced concrete using vertical #7 rebar spaced 39"
3. 9.5 inches thick reinforced concrete using vertical #6 rebar spaced 39"
4. 11.5 inches thick reinforced concrete using vertical #4 rebar spaced 48". This last entry has footnote h on it.
8. Read footnote h: "A plain concrete wall with a minimum thickness of 11.5 inches is permitted, provided minimum specified compressive strength of concrete, f'c , is 3,500 psi."
Of the four choices given as answers to the question, the best one is D, 11.5 inches, for a plain concrete wall, as allowed by footnote h. You don't need to build a reinforced concrete wall in this particular situation if you also specify that the concrete needs to have a minimum compressive strength of 3500 psi.

Q.E.D.

Side note -- To continue with the design example:

Note in step 1 that you also need to comply with Section R402.2. When you go to R402.2 you find additional specs on the concrete that you need to meet and it refers you to Table R402.2. Table R402.2 has various minimum compressive strengths for concrete based upon use and weathering potential. Footnote b in Table R402.2 sends you to Table R301.1. Table R301.1 sends you to Figure R301.2(3). From Figure R301.2(3), if I'm building my wall in Florida, the weathering potential is "negligible". If I'm building my wall in New York, the weathering potential is "severe".

Go back to Table R402.2. Enter the table on the row for foundation walls exposed to the weather and read across to the negligible and severe columns.

If I'm in an area with negligible weathering potential, such as Florida, Table R402.2 says my concrete needs to have a minimum compressive strength of 2500 psi. Since I already specified my concrete wall at a minimum of 11.5 inches thick and 3500 psi compressive strength, I'm done because Table R404.1.1(5) controls.

If I'm in an area with severe weathering potential, such as New York, Table R402.2 says my concrete needs to have a minimum compressive strength of 3000 psi, which is still met by the 3500 psi that was determined from Table R404.1.1(5). But that 3000 psi in Table R402.2 has a footnote d, which says I need to add another spec to my concrete: "Concrete shall be air-entrained. Total air content (percent by volume of concrete) shall be not less than 5 percent or more than 7 percent."

Final answer to the question, for a plain concrete wall, under the 2006 IRC is:

A minimum thickness of 11.5 inches using concrete with a minimum compressive strength of 3500 psi, AND if you are in one of the areas identified in Figure R301.2(3) as having "severe" or "moderate" weathering potential, the concrete must be air entrained with a total air content (percent by volume of concrete) that is not less than 5 percent or more than 7 percent.

I don't think they intended the solution to this question to be this complex, which is why I said in my first post:

The procedure to arrive at the correct answer using the 2006 code and the question data, and the 2003 table reference, leads me to believe that the question was not updated for the 2006 code but was carried over from 2003.

In other words, I think that the question and the answers were written based on the 2003 IRC, and for the 2006 IRC they probably should have adjusted the question inputs so that you wouldn't have to rely on footnote h in order to get the correct answer.

Brandon

16. ## Re: Help on ICC practice Exam Question

Brandon,

Thank you for the complete walk through on that.

17. ## Re: Help on ICC practice Exam Question

WoW!

That was very educating.
There is nothing out there that could replace this forum. It covers all bases in one place.

Thanks Guys!

18. ## Re: Help on ICC practice Exam Question

Originally Posted by RobertSmith
You chosed the 11.5 min thickness BECAUSE the other options under 5.5, 7.5, and 9.5 are for reinforced concrete ONLY, not for PC ,so that drove you to #4@48, footnote H which would be the best answer, correct?
No, Brandon (this is what I think) understood what they were asking better than I did (I 'over-thought' the question) and, when the answer was not there, he looked down to the next row (showing with rebar) and saw the footnote 'h' and said 'I had better read that', and footnote 'h' said 'you can use plain concrete if' and that was the answer, because the 'if' was not specified.

I don't have the IRC 2003 so I can't compare the ease of getting the answer, but I bet you be write that they didn't update the question, I wouldn't think they would ask you a question where you had to think this hard.
I was going to post this to Brandon, but you are covering it as well: I suspect they *INTENTIONALLY* wrote the question that way to see how many would catch and read the footnote and not try to over-think it. They certainly caught me, so I missed that answer and got it wrong ... well, actually, I did get the right answer (11.5"), but I did it wrong (used the wrong column).

In this case I got the right answer, but in a similar question I might not have arrived at the right answer - so doing it correctly is important.

19. ## Re: Help on ICC practice Exam Question

My answer was wrong? I based it on all of the details given (or so I thought).

20. ## Re: Help on ICC practice Exam Question

(I'm trying the "multi-quote this message" feature with this post ... let's see how this works ... )

Originally Posted by Jerry Peck
Brandon,

Thank you for the complete walk through on that.
Originally Posted by RobertSmith
Wow, thanks Jerry/Brandon....
Originally Posted by Mike Schulz
WoW!

That was very educating.
There is nothing out there that could replace this forum. It covers all bases in one place.

Thanks Guys!
You're welcome. I've learned a lot from this forum. I've learned how to apply what I know to the practice of inspecting homes, I've learned things I didn't know, I've learned to recognize some things that I still need to learn, and I've learned a lot about the business-side of being a home inspector. There's a high failure rate in this profession and I think this forum (and some others like it) greatly improves my odds of long-term success. I'm happy to give something back.

Originally Posted by RobertSmith
yes, this is a 2006 practice exam question for from the ICC online practice test for 2006 Residential B1 certification....if you guys have problems with it, I'm screwed!

Brandon,

- I understand why you went from 7.5 to 8ft unbalanced backfill...if 7.5 ft isn't listed drop to next highest level.

- I understand why you chose SC column with 60 psf.

Now,

where i need a little more clarification......

You chosed the 11.5 min thickness BECAUSE the other options under 5.5, 7.5, and 9.5 are for reinforced concrete ONLY, not for PC ,so that drove you to #4@48, footnote H which would be the best answer, correct?

I don't have the IRC 2003 so I can't compare the ease of getting the answer, but I bet you be write that they didn't update the question, I wouldn't think they would ask you a question where you had to think this hard.
Originally Posted by Jerry Peck
No, Brandon (this is what I think) understood what they were asking better than I did (I 'over-thought' the question) and, when the answer was not there, he looked down to the next row (showing with rebar) and saw the footnote 'h' and said 'I had better read that', and footnote 'h' said 'you can use plain concrete if' and that was the answer, because the 'if' was not specified.
What drove me to the correct answer is that they wanted a "plain concrete" wall. Reading across the 8 foot row under the columns under the SC soil class, the four entries all call for reinforced concrete. When I first saw that, I thought "oh, crap!" Then I saw footnote h attached to the entry in 11.5 inch column, I read footnote h (which says you can use a plain concrete wall in this case if you increase the strength of the concrete), and I thought "those sneaky bastards!"

Originally Posted by Jerry Peck
I was going to post this to Brandon, but you are covering it as well: I suspect they *INTENTIONALLY* wrote the question that way to see how many would catch and read the footnote and not try to over-think it. They certainly caught me, so I missed that answer and got it wrong ... well, actually, I did get the right answer (11.5"), but I did it wrong (used the wrong column).

In this case I got the right answer, but in a similar question I might not have arrived at the right answer - so doing it correctly is important.
You could be right about the intent. The question does require someone to pick up on the fact that footnote h is there and that it applies to this problem. And since the question says nothing at all about the strength of the concrete, only that they want a plain concrete wall, D is the correct answer.

In a prior life some of my job duties were to review and write questions for a certification exam. One of the things you want to avoid when you construct a question and answer set is having people use the wrong method but still get the right answer. In that sense, this question still needs some tweaking of the inputs to make it better.

Originally Posted by imported_John Smith
My answer was wrong? I based it on all of the details given (or so I thought).
John, your answer and methods are correct by using the 2003 IRC. Things changed in the 2006 version.

21. ## Re: Help on ICC practice Exam Question

Thanks Brandon. But I really wanted to hear Jerry say it.

22. ## Re: Help on ICC practice Exam Question

Originally Posted by Brandon Chew
John, your answer and methods are correct by using the 2003 IRC. Things changed in the 2006 version.
Originally Posted by imported_John Smith
Thanks Brandon. But I really wanted to hear Jerry say it.
Not a problem. (Although Brandon is a better source than I am.)

"John, your answer and methods are correct by using the 2003 IRC. Things changed in the 2006 version."

23. ## Re: Help on ICC practice Exam Question

Wendell,
The Key word is "plain concrete"
(all of the wall thicknesses require reinforced concrete instead of plain concrete,)

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