# Type of Construction



## BayPointArchitect (Apr 19, 2016)

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


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## steveray (Apr 20, 2016)

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....


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## Builder Bob (Apr 20, 2016)

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_.


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## steveray (Apr 20, 2016)

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...


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## BayPointArchitect (Apr 20, 2016)

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!


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## Builder Bob (Apr 20, 2016)

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.


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