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Construction Type A vs. B?
January 30, 2018
7:31 am
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pmiller@co.worcester.md.us
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TABLE 601
FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (HOURS)

January 25, 2018
11:46 am
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jopoco2005@yahoo.com
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In reference to my previous post. The A and B classifications are not in the ICC building code. Clarification can be found in Code Commentary that A is protected and B is unprotected. It would be extremely helpful and much more clear as to the true meaning of this if a simple explanation were included in the actual code. Just saying.

January 25, 2018
11:11 am
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jopoco2005@yahoo.com
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I am not seeing this in below responses.  The type A and B designation does not refer to the actual structural member, but whether or not it is protected by a non combustible material, (i.e. gyp board, spray on coating,....). I have looked in Chapter 6 for clarification of which is which, and do not see it. Judging by Chapter 5 figures for Height and Area limitations, I am assuming that Type A is protected, and type B is unprotected. Correct?

August 10, 2006
9:30 pm
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tjacobs
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[QUOTE]If I wish to build a 6000 sq. ft. 2 story office building using tilt-up const. with all non-combustible materials (never mind WHY I would want to do this) I could easily call it 5B construction and be compliant. Remember, any single building could be classified as more than 1 construction type.[/QUOTE]602.1 says ONE of the types of construction. If you design a Type IB or IIB building but classify it as Type VB on the plan, I will make you do everything in the code required of a VB, not IB or IIB.

No problem.

August 9, 2006
4:43 pm
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paul sweet
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The old BOCA codes used the terms "Protected" and "Unprotected" for types 3, 4 & 5 construction. For Type 2 (noncombustible) both A & B were "Protected" and 2C was "Unprotected". For Type 1 both A & B were protected. A always had the highest fire rating.

August 9, 2006
4:31 pm
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thelunatick1
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BHardy,
A and B do not refer to protected and unprotected.
Rather I would perceive them as Option A and Option B.
However, B is always a lesser rating.

Tables involve, but not limited to, include: 302.3.3, 503, 601, 602, chapter 7 (704.8)

Combustible and NonCombustible construction is a different beast altogether.

COF forgot to mention that placement on the site will factor into this, directly and indirectly.
If the building is clear 60 feet all around, it may become eligible as an unlimited area building. But if only, say 20 feet clear around, then it does not qualify.

But I would begin first looking at what area will be allowed and go from there.

August 9, 2006
3:41 pm
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jiano
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Brent, I think the answer to your question is yes, height and area requirements are the primary consideration in choosing between construction types and their A and B variations.

But the selection might not be made "solely" on that basis. There are other code requirements that sometimes set minimum construction type requirements as well.

August 9, 2006
2:34 pm
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paul curry
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I agree with cof, but conversely:

If I wish to build a 6000 sq. ft. 2 story office building using tilt-up const. with all non-combustible materials (never mind WHY I would want to do this) I could easily call it 5B construction and be compliant. Remember, any single building could be classified as more than 1 construction type.

August 9, 2006
2:29 pm
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cof
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Brent; All three of the previous posts are absolutely correct. The construction classification is not only a function of the requirements of Table 503 but it is also a function of all of Chapter 5. The height and area figures in Table 503 are ''raw'' numbers and do not reflect any increases allowed in Chapter 5, such as sprinklers (Sect. 504) or area modifications (Sect. 506). There is no ''default'' for construction types unless the designer doesn''t want to attempt to maximize the application of the Code.
As an overly simple example; if I wanted to construct an 3 story 20,000sf occupancy group ''B'' building but didn''t want to take the time to consider any height and area allowances; the minimum construction types allowed based on Table 503 would be IIB or IIIA, whereas if I do some code work I might find that I could build the building as a V-B building if I wanted to sprinkler it and it had a fully open perimeter.
The example is of course not taking into consideration any other code sections or requirements.

August 9, 2006
1:02 pm
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paul curry
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sp_Print Print Post Post #10

No, what determines if it is 3A or 3B is the fire resistive ratings of the various elements specified in table 601.

August 9, 2006
12:21 pm
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bhardy
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sp_Print Print Post Post #11

Walt,

So then are you implying that whether a building with a pre-determined use is 3a or 3b is soley a function of requirements needed to maintain height and area restrictions in table 503. So that if a buildings height and area was sufficiently low, based on table 503, then the classification would by default become 3b. 3a would then only be for those cases where a type 3 building exceeds any of the height/heating-oil-tank-hot-exam-oregon rea limitations in the 3b catagory?

Thanks,

-Brent

August 9, 2006
11:22 am
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walt
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sp_Print Print Post Post #12

Table 601 tells you what the fire-resistive requirements are of the type of construction you select based on the size, use, and height and area restrictions (Table 503).

August 9, 2006
11:19 am
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kdavidthomas
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sp_Print Print Post Post #13

"redundantly"

Welcome to our world.
The inference comes from table 601. The rating requirements for ''b'' types are generally 0, hence the concept of "unprotected" although exceptions and other provisions of the code can cuase FR construction to come into play.