The most widely accepted flame-spread classification system appears in the National Fire Protection Association Life Safety Code, NFPA No. 101. NFPA 101 primarily applies this classification to interior wall and ceiling finish materials. Roof coverings must meet a different set of criteria. Exterior Wall Construction Exterior wall construction can be classified by its fire-resistance. A fire-resistive rating is the time that exterior wall construction can withstand fire exposure as determined by a standard fire test.
Most home construction is currently non-rated.
This is not to say that non-rated homes have no fire resistance, it s just less than one hour. Typical home construction provides protection of about 40 to 50 minutes. The following is Table No. The Fire Resistance Directory , published by the Underwriters Laboratory, lists many examples of fire-resistant exterior wall construction. Log and heavy timber construction is also considered 1-hour construction.