Unlimited Area Buildings and Type of Construction

[ewenme]

I have a 130,000 sq. ft. building, with mixed use occupancy of M & S-1. The Architect is claiming Unlimited Area AND Type V-B construction, quoting '09 IBC 507.3. I disagree with his call, citing Table 503, and Section 508.3.2, which references 503.1. The building is fully sprinklered throughout, however there are no fire separation walls. FYI: This is a Wal-Mart addition and full gut-remodel. I'd like to hear how others would call it.

 

[mark handler]

507.3 Sprinklered, one story. The area of a Group B, F, M or S building no more than one story above grade plane shall not be limited when the building is provided with an automatic sprinkler system throughout in accordance with Section 903.3.1.1 and is surrounded and adjoined by public ways or yards not less than 60 feet in width.

1. Do they have the yards?

2. TABLE 508.4, separation not required

 

[fatboy]

I'm with Mark.........

 

[mtlogcabin]

TABLE 503

ALLOWABLE HEIGHT AND BUILDING AREASa

a. See the following sections for general exceptions to Table 503:

1. Section 504.2, Allowable height increase due to automatic sprinkler system installation.

2. Section 506.2, Allowable area increase due to street frontage.

3. Section 506.3, Allowable area increase due to automatic sprinkler system installation.

4. Section 507, Unlimited area buildings.

4 sends you to section 507. So I agree with Mark do you have the 60 foot open yard requirement? If you do it is okay.

 

[RLGA]

I concur with the above. If the yards are provided, then an unlimited, Type VB building is permissible for those occupancy groups. Separation by fire barriers per 508.4 or fire walls for separate buildings, are not required.

 

[High Desert]

Table 503 has a footnote a., 4 that sends you to 507 for unlimited area buildings, so you're out of Table 503 when applying the provisions of 507. You can have the various occupancies and not call it mixed occupancy and still use the unlimited area building provisions.

 

[ewenme]

Maybe I'm dense, but if you have a single occupancy building, I would agree with you. However, Section 508.3, limits the area to those figures in Table 503... and for M and S-1 the limits are way less than 130,000 sq. ft. of Type V-B construction. I do believe they have met the requirements for Type I-B using fire retardent wood for the roof sheathing and CMU, non-combustible materials elsewhere. Why wouldn't they want to designate Type I-B [non-rated] for the unlimited area structure which is protected by sprinklers throughout?

If, as you all have noted, that unlimited area buildings are allowed, why does the code limit the area of mixed occupancy buildings to the values in Table 503? Maybe I'm splitting hairs or points... but there must be a reason, unless the code is just useless! :devil

 

[permitguy]

Section 508.3, limits the area to those figures in Table 503

Not quite. Always read the footnotes.

Why wouldn't they want to designate Type I-B [non-rated]

Type I-B is not "non-rated." Type V-B will be much cheaper, will give them greater design flexibility, and is permissible by code.

 

[mark handler]

There are area limits if you do not have the fire fighting yards.

 

[High Desert]

See the following ICC interpretation. Althought the question was asked about a 2-story unlimited building, it only seems to reason that it would also apply to a 1-story.

http://www2.iccsafe.org/cs/committeeArea/pdf_file/BU_03_44_06.pdf

 

[texasbo]

ewenme, Mark and the others are correct; the yards and the sprinklers are the difference. For the occupancies noted, even with mixed occupancies, you get unlimited area with fully sprinklered buildings with the yards.

 

[mtlogcabin]

503.1 General.

The height and area for buildings of different construction types shall be governed by the intended use of the building and shall not exceed the limits in Table 503 except as modified hereafter.

As Mark pointed out the 60 ft open yards allow the modification in area according to footnote "a" item 4

 

[ewenme]

They do have the 60 ft. yards, except at the back where the yard goes up a steep slope. However, I'm still stuck in the 'endless do-loop' created by Section 508.3, which 'comes after' 507.3... as hereafter modified. If mixed use occupancies are not big deal, then why don't we just eliminate them from the code book according to the Table at 508?

In the last class I took on use and occupancy, A= rated construction, B= non-rated construction. Permitguy, can you show me where it says "B" does not equal non-rated?

 

[ewenme]

:banghd BTW: Thank you all for the very good discussion. :inspctr

 

[High Desert]

ewnme, if you didn't have the 60 ft. yards, you would be in the mixed occupancy section and the building would be subject to the provisions of 508.4, Separated Occupancies and wouldn't qualify for the unlimited area. Then you would be back at Table 503. Did you read the ICC interpretation? Mixed occupancies are a big deal if you can't meet nonseparated uses or unlimited area.

 

[permitguy]

In the last class I took on use and occupancy, A= rated construction, B= non-rated construction. Permitguy, can you show me where it says "B" does not equal non-rated?

That is an extremely over-simplified explanation of the A and B. Look at the requirements for Type I-B construction in table 601, and you will see what I was getting at.

 

[JBI]

ewenme - It's a bit more complex than A=rated and B=non-rated... more accurate to say that A's have higher ratings than their corresponding B's. BTW, I agree with the majority on the OP. Like it or not, the proposal complies (just make sure the yards ALL count and the sprinklers are done correctly).

 

[ewenme]

Actually, in doing the plan review, I was impressed with the completeness of the plans. I only found one small structural detail missing: support for a 3 1/8" precast cap for a wall that is ledgered against a taller wall. I questioned the architect, 'where can I find the detail for the support of the precast cap?'... And he replied: sorry, it's not there. I missed it and the engineer missed it. The architect is also going to send me an ICC commentary on the ulimited area buildings. The proposed building will have about 40 feet level at the back of the building, then it's uphill at a 3:1 slope to the property line, which ends at a road that is taller than the roof of the proposed building.

 

[mark handler]

The proposed building will have about 40 feet level at the back of the building, then it's uphill at a 3:1 slope to the property line, which ends at a road that is taller than the roof of the proposed building.

Still maybe okay

507.5 Reduced open space. The public ways or yards of 60 feet (18 288 mm) in width required in Sections 507.2, 507.3, 507.4, 507.6 and 507.11 shall be permitted to be reduced to not less than 40 feet (12 192 mm) in width provided all of the following

requirements are met:

1. The reduced width shall not be allowed for more than 75 percent of the perimeter of the building.

2. The exterior walls facing the reduced width shall have a minimum fire-resistance rating of 3 hours.

3. Openings in the exterior walls facing the reduced width shall have opening protectives with a minimumfire protection rating of 3 hours.

 

[brudgers]

I think the OP is having a bit of a hangup over VB unnecessarily.

Just because combustible construction is allowed in VB doesn't mean it will be used.

Most likely non-combustible materials will be used due to insurance rates.

VB just means that structural elements and exterior walls will not need to be rated due to construction type* - And the insurance carrier probably won't care about that.

* (other code requirements may require rating).

 

[texasbo]

Still maybe okay507.5 Reduced open space. The public ways or yards of 60 feet (18 288 mm) in width required in Sections 507.2, 507.3, 507.4, 507.6 and 507.11 shall be permitted to be reduced to not less than 40 feet (12 192 mm) in width provided all of the following

requirements are met:

1. The reduced width shall not be allowed for more than 75 percent of the perimeter of the building.

2. The exterior walls facing the reduced width shall have a minimum fire-resistance rating of 3 hours.

3. Openings in the exterior walls facing the reduced width shall have opening protectives with a minimumfire protection rating of 3 hours.

Whoa, hold on. The code says yards or public ways. It doesn't say they have to be paved, be fire lanes, nor does it regulate the slope. Definition of yard does not include slope or grade. If there are 60' yards, then it is eligible for unlimited area.

 

[Builder Bob]

TexasBO - read the commentary - while not code, it does provide logic for the unlimited building to be built when tradeoffs are provided - i.e. sprinklers AND Fire Department Access..... Firetrucks cannot fly nor does water from firefighting nozzles (master streams) have unlimited reach - gravity will bring the water stream down and air resistance will cause the master stream to break apart .......

 

[texasbo]

The fact remains, the code says yards or public ways. A yard could be filled with landscaping, water features, sculpture gardens, or just soft, mushy, unpaved ground, all of which would not be conducive to fire trucks. If the code intended fire truck access, it would have said fire lanes.

And I think the intent is increased separation from other structures as much or more than it is for fire access. But regardless, a yard is a yard.

Lastly, the authors of the handbooks are no more experts than many of the members here; I'd place my trust in the interpretation of members of this forum before I would ICC.

 

[RJJ]

I tend to agree with Texasbo on this yard thing, But I believe the IFC states some different language for fire access. Now I am going to have to go to the truck and read those sections.