Type of Construction

[BayPointArchitect]

Hey folks.

I just wanted confirmation that a steel framed building that has been polluted with wood framed interior partitions (non-load bearing) may be down-graded from a Type IIB construction to Type IIIB. The exterior walls are not 2 hour rated. The steel columns supporting the roof are not protected. There is an issue with proximity to the property lines but my focus is only on trying to fit this existing 15,000 S.F. building into the Type IIIB category.

See attached illustration. The illustration is conceptual.

https://www.dropbox.com/s/6y0qc6dvu77vyn7/Construct-Type.pdf?dl=0

Thank you!

ICC Certified Plan Reviewer

NFPA Certified Fire Plan Examiner

 

[steveray]

If you get the 2hr exterior it is can be IIIB...I guess the question is if the primary frame is "part of" the exterior wall....

 

[Builder Bob]

footnote T601

g. Not less than the fire-resistance rating as referenced in Section 704.10

704.10 Exterior structural members.

Load-bearing structural members located within the exterior walls or on the outside of a building or structure shall be provided with the highest fire-resistance rating as determined in accordance with the following:

1. As required by Table 601 for the type of building element based on the type of construction of the building; 2. As required by Table 601 for exterior bearing walls based on the type of construction; and 3. As required by Table 602 for exterior walls based on the fire separation distance.

 

[steveray]

Thanks BB!...But in theory, you could have a IIB building that qualified as IIIB if the primary frame was completely inside the exterior nonbearing wall...And everything could be unrated barring FSD at that point...

 

[BayPointArchitect]

Bingo!

Given that this is a typical metal building, there is no "exterior bearing wall" which would otherwise need to be 2 hour fire-rated for Type IIIB.

And the primary structural frame does not need to be rated for Type IIB, IIIB and VB.

Conclusion:

If you discover that a non-sprinkled, 15,000 S.F. metal building (Type IIB) has had interior offices built (without a permit - damn it) using wood framing, it is possible to classify that building as Type IIIB rather than Type VB. The critical difference is the base allowable area (19,000 s.f. versus 9,000).

Thanks again!

 

[Builder Bob]

Not exactly, The columns for the pre-engineered metal building are the load bearing structural members of the building along with the purlins, the metal sheeting is just a veneer for weather proofing...

WALL. A vertical element with a horizontal length-to-thickness ratio greater than three, used to enclose space.

Cavity wall. A wall built of masonry units or of concrete, or a combination of these materials, arranged to provide an airspace within the wall, and in which the inner and outer parts of the wall are tied together with metal ties. Composite wall. A wall built of a combination of two or more masonry units bonded together, one forming the backup and the other forming the facing elements. Dry-stacked, surface-bonded wall. A wall built of concrete masonry units where the units are stacked dry, without mortar on the bed or head joints, and where both sides of the wall are coated with a surface-bonding mortar. Masonry-bonded hollow wall. A multi-wythe wall built of masonry units arranged to provide an air space between the wythes and with the wythes bonded together with masonry units. Parapet wall. The part of any wall entirely above the roof line. WALL, LOAD-BEARING. Any wall meeting either of the following classifications:

1. Any metal or wood stud wall that supports more than 100 pounds per linear foot (1459 N/m) of vertical load in addition to its own weight. 2. Any masonry or concrete wall that supports more than 200 pounds per linear foot (2919 N/m) of vertical load in addition to its own weight. WALL, NONLOAD-BEARING. Any wall that is not a load-bearing wall.

AHJ interpretation - does the insulation and attachment of materials make the columns and purlins carry more than 100 lbs/ linear foot of exterior wall and cladding.