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IBC2012 Type of Construction and Fire Resistance

H

hjin25

Member
Joined
Aug 7, 2013
Messages
3
Location
Los Angeles
I am new to the building code, and wanted to see if anyone can provide guidance on determining the type of construction given a set of as-builts.

Occupancy: B

Stories: 2

Story Height: 20' (lower), 18' (upper)

Floor Area: 35,000 sf/floor

Vertical system: Combination of r/c, precast concrete panels, steel column

Horizontal system: slab-on-grade, concrete on metal deck (floor) and metal deck on steel beams (roof)

Fully sprinklered

I am missing architectural general notes. Interior partitions have 1 hour rated partitions on specific areas within the building. I don't see anything about additional protection on structural members in terms of fire resistance. Would this be geared towards Type IIB or IB? I read somewhere that if roof is non-combustible, then it falls under Type I.

I greatly appreciate any advice as I have just started learning the code.
 
hjin25 said:
I am new to the building code, and wanted to see if anyone can provide guidance on determining the type of construction given a set of as-builts.Occupancy: B

Stories: 2

Story Height: 20' (lower), 18' (upper)

Floor Area: 35,000 sf/floor

Vertical system: Combination of r/c, precast concrete panels, steel column

Horizontal system: slab-on-grade, concrete on metal deck (floor) and metal deck on steel beams (roof)

Fully sprinklered

I am missing architectural general notes. Interior partitions have 1 hour rated partitions on specific areas within the building. I don't see anything about additional protection on structural members in terms of fire resistance. Would this be geared towards Type IIB or IB? I read somewhere that if roof is non-combustible, then it falls under Type I.

I greatly appreciate any advice as I have just started learning the code.
Click to expand...
new or existing building???
 
hjin25 -

Old terminology would have been Type I = Fire resistive and Type II = Non-combustible.

The required ratings based on Construction Type are in Table 601 (below, don't forget to check applicable footnotes...).

The base line for most elements in Type IB is 2 hours, which includes most load bearing elements. The steel columns, lacking any specific protection, will likely land you in Type IIB. You did not indicate if the 1 hour partitions are load bearing (partitions generally aren't). Your two basic options are:

1 - Classify it and let the design professional justify a different classification, or

2 - Ask the DP to identify the ratings for critical areas identified in the Code and the table.

SECTION 601 GENERAL

TABLE 601 FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (HOURS)

BUILDING ELEMENTTYPE I TYPE II TYPE III TYPE IVTYPE V
ABAdBAdBHT AdB
Primary structural frameg (see Section 202 ) 3a 2a 1 0 1 0 HT 1 0
Bearing walls
Exteriorf, g 3 2 1 0 2 2 2 1 0
Interior 3a 2a 1 0 1 0 1/HT 1 0
Nonbearing walls and partitions

Exterior 		See Table 602
Nonbearing walls and partitions

Interiore 		0 0 0 0 0 0 See Section 602.4.6 0 0
Floor construction and associated secondary member

(see Section 202 ) 		2 2 1 0 1 0 HT 1 0
Roof construction and associated secondary members

(see Section 202 ) 		11/2b 1b,c 1b,c 0c 1b,c 0 HT 1b,c 0

For SI: 1 foot = 304.8 mm.
a. Roof supports: Fire-resistance ratings of primary structural frame and bearing walls are permitted to be reduced by 1 hour where supporting a roof only.
b. Except in Group F-1, H, M and S-1 occupancies, fire protection of structural members shall not be required, including protection of roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below. Fire-retardant-treated wood members shall be allowed to be used for such unprotected members.
c. In all occupancies, heavy timber shall be allowed where a 1-hour or less fire-resistance rating is required.
d. An approved automatic sprinkler system in accordance with Section 903.3.1.1 shall be allowed to be substituted for 1-hour fire-resistance-rated construction, provided such system is not otherwise required by other provisions of the code or used for an allowable area increase in accordance with Section 506.3 or an allowable height increase in accordance with Section 504.2. The 1-hour substitution for the fire resistance of exterior walls shall not be permitted.
e. Not less than the fire-resistance rating required by other sections of this code.
f. Not less than the fire-resistance rating based on fire separation distance (see Table 602).
g. Not less than the fire-resistance rating as referenced in Section 704.10

602.2 Types I and II.

Types I and II construction are those types of construction in which the building elements listed in Table 601 are of noncombustible materials, except as permitted in Section 603 and elsewhere in this code.
 
The table grid did'nt paste in, sorry about that. The A & B sub-classes need to be shifted right...
 
It's an exisiting that was built in the 80's. Not sure what code was used, but strictly going by IBC2012 for a specific reason...
 
Thank you for the advice. I guess without having any design docs or specs, it's a bit hard for me to determine what the assumptions were just by looking at the as-built plans.

Only specific fire rating that was called out on the plan was the interior non-load bearing partition wall that was storing somewhat important equipments/informations. For building elements to have 2 or 3 hour rating, are they specifically called out? or by default, are all members have 0 hour rating without any additional protection?

Btw, DP does not exist as the building is old, and can't find any documentation other than the as-builts...
 
Ah, the total lack of code data on the drawings--I've never seen that on an old set of drawings.(sarcasm off)

If the entire building and any new work is being evaluated under the 2012 IBC, then there are a couple of things you have to keep in mind.

1. Occupancy separation requirements under the 2012 IBC are not the same as under the legacy codes. Fire-resistance ratings have increased for some occupancy separations, so what may have been a conforming occupancy separation under the old code may not qualify as an occupancy separation in the 2012 IBC. Thus, the building or portion of building with a nonconforming occupancy separation must be considered as nonseparated occupancies or the wall(s) must be replaced or modified to comply with current fire ratings.

2. Just because a building is constructed of noncombustible materials does not require it to be of Type I or II construction. If the height and area is within the allowable height and area for a combustible construction type, then that construction type can be used. A combustible construction type may give you some relaxation on other code requirements. However, based on the floor area of your project, it looks like only Type IIIB would be applicable, assuming the exterior wall qualifies as 2-hour construction. Otherwise, the Type IIB construction seems most appropriate for height, area, and existing fire-resistive construction (or lack thereof).
 
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Also being sprinkled should help you

Not sure if anyone has a link to trade offs
 
Some of the trade-offs are in the footnotes for the table, like an automatic reduction in ratings for some elements with a full NFPA 13 sprinkler system (footnote d for example). Conversely some limits to reductions are in footnotes as well.

It would be helpful to us if the OP were a little less cryptic about the project -

Why the IBC for an existing building as opposed to the IEBC?

Why the need to evaluate the building without a DP?

Where is the project located? (OP is in LA, but the project location is not disclosed...)
 
Going to go out on a limb and make some assumptions. If indeed it is a B Occupancy fully sprinklered it would appear Type II-B would permit 4 stories and 69000sf per floor (Table 503 with sprinkler increase), yard increases not included. If......”full” yardage increase were permitted it would appear Type V-B would permit a 3 story building with 33750sf per floor. Based on the original post it would appear it is not a “Type A” construction type. I would check the yardage increases and confirm the building is over 33750sf (sharpen your pencil, calculate the area from the INTERIOR face of exterior walls and discount all shafts). As mentioned above, always chose the LEAST restrictive type of construction even though you may build it to what appears to be a “higher” type of construction, i.e. a Type V-B building can be constructed of non-combustible construction but still be classified as a Type V-B building. Caveat, the above is just my guess of what the building “may be”, with-out full analysis.
 
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