Openings in Type IIIB Construction

[DOD22]

Curious how exterior window openings are achieved in type IIIB construction without opening protectives. If exterior bearing walls are required to be two hour rated, does that mean openings are not permitted anywhere where the wall is load bearing?

 

[RLGA]

Curious how exterior window openings are achieved in type IIIB construction without opening protectives. If exterior bearing walls are required to be two hour rated, does that mean openings are not permitted anywhere where the wall is load bearing?

Exterior walls are not assemblies like fire walls, fire barriers, fire partitions, and smoke partitions. The fire resistance required by Table 601 is solely for the purpose of protecting the structural integrity of the building and not preventing the spread of fire. A fire-rated loadbearing exterior wall is permitted to have openings, and are only required to be protected in accordance with Section 705.8 based on the fire separation distance.

 

[DOD22]

Exterior walls are not assemblies like fire walls, fire barriers, fire partitions, and smoke partitions. The fire resistance required by Table 601 is solely for the purpose of protecting the structural integrity of the building and not preventing the spread of fire. A fire-rated loadbearing exterior wall is permitted to have openings, and are only required to be protected in accordance with Section 705.8 based on the fire separation distance.

Thank you for the quick response. Where does the code make the distinction that opening protectives as described in Table 716.1(2) are required only based on FSD and the requirements set by the construction type?

 

[RLGA]

Section 705.5 addresses exterior wall fire-resistance ratings. Section 705.8 and Table 705.8 address exterior wall openings.

 

[Paul Sweet]

Type III construction makes little sense without the historical background. It used to be called "Ordinary Construction". All exterior bearing walls were masonry, and interior construction was generally wood frame or metal framing, or a combination. All buildings in built-up areas of cities, which were designated as the "Fire Limits", were required to be Ordinary Construction or Fireproof to prevent building fires from spreading and becoming conflagrations.

In the mid 1980s BOCA, and I guess the other model codes, did away with fire limits and substituted fire-resistance requirements for exterior walls based on distance from property lines. The 2-hour exterior wall requirement for Type III stems from the masonry bearing walls of Ordinary Construction typically having a fire rating of 2 hours or more.

 

[Yikes]

In training our architectural staff on structural fire ratings vs. opening protection, occupancy separation, dwelling unit separation, etc.) I show them this old ad from the late 1960s. The wall framing itself is protected, but you are not protected from your neighbor.