100 Building.

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Section/Paragraph: 100 Building.

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Building. A structure that stands alone or that is cut off from adjoining structures by fire walls with all openings therein protected by approved fire doors.

Substantiation:

"therein" is an archaic term which is considered to reduce clarity according to NEC_StyleManual_2011.pdf 3.3.4.

 

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Section/Paragraph: 100 Building.

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Building. A structure that stands alone or that is cut off from adjoining structures by fire walls with all openings therein protected by approved fire doors.

Substantiation:

"therein" is an archaic term which is considered to reduce clarity according to NEC_StyleManual_2011.pdf 3.3.4.

They're talking about openings in firewalls. Keep in mind a firewall and a fire rated partition are two different animals.

A firewall means you have, by definition, a separate building on each side of the firewall. A door in a firewall is a firedoor. Traditionally these are 4 hour walls with 3 hour doors.

A fire rated partition is used for occupancy separation, to rate a means of egress and for other purposes. The areas of the building on each side of a fire rated partition are collectively the same building. A door in a fire rated partition is a fire rated door but not a firedoor. These are most commonly 1 or 2 hour walls with 20 minute to 90 minute doors.

The reason a door in a rated assembly may have a lower rating than the wall is because we normally don't place combustibles against a door like we do with a wall. Fire does not necessarily burn through a wall; enough heat gets generated by burning combustibles that the heat radiates through the wall. The absence of combusitbles at a door means the intent of the rated assembly has been achieved.

The cited word "therein" applies only to the firewall.

Hope this helps.