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Types of construction
- Thread starter DLC
- Start date
MtnArch
SAWHORSE
I'm speaking from the California Building Code, but would assume your codes are similar: Rather simplistically, the 'A' refers to fire-rated construction and the 'B' is a non-rated construction.
Someone please correct me if I have this wrong!
Someone please correct me if I have this wrong!
Coug Dad
Platinum Member
A and B are subsets of the main construction type.
II-A is non combustible with a fire resistive rating
II-B is non combustible without a fire resitive rating
Both I-A and I-B are rated. In the other types, MT is correct.
II-A is non combustible with a fire resistive rating
II-B is non combustible without a fire resitive rating
Both I-A and I-B are rated. In the other types, MT is correct.
IA and IB both require fire-rated constructed, so B isn't always nonrated.
I like to say that the "A" is more fire-resistive and the "B" is less fire-resistive. Depending on which one you use depaends on the building's allowable area and height.
I like to say that the "A" is more fire-resistive and the "B" is less fire-resistive. Depending on which one you use depaends on the building's allowable area and height.
Coug Dad
Platinum Member
The definition of each construction type is in Section 602.2 through 602.5
Table 601. Each column identifies the fire-resistive requirements for each construction type, A and B, if applicable.
Not considering any increases, if you have a 3-story Group B building that has a maximum floor area per story of 20,000 sq. ft., then you could classify it as either Type IIB, IIIA, or IV construction. If you use Type IIB, you are not required to have any fire-resistance-rated construction; however, it must be constructed of noncombustible materials. If you use Type IIIA, you must have 2-hour exterior bearing walls, and 1-hour construction elsewhere (except interior nonbearing walls), but you can use noncombustible materials (except that exterior walls must be noncombustible or fire-retardant-treated wood). If you use Type IV, then you must comply with the heavy timber requirements.
It's a designer's choice which route they take.
Not considering any increases, if you have a 3-story Group B building that has a maximum floor area per story of 20,000 sq. ft., then you could classify it as either Type IIB, IIIA, or IV construction. If you use Type IIB, you are not required to have any fire-resistance-rated construction; however, it must be constructed of noncombustible materials. If you use Type IIIA, you must have 2-hour exterior bearing walls, and 1-hour construction elsewhere (except interior nonbearing walls), but you can use noncombustible materials (except that exterior walls must be noncombustible or fire-retardant-treated wood). If you use Type IV, then you must comply with the heavy timber requirements.
It's a designer's choice which route they take.