78
3220.037
Anonymous
Fire Resistance Characteristics
Paper
American Insurance Association
1964
After January 1964
1-15
Y
The fire resistance ratings for masonry walls fall generally into two broad methods of classification.The first method lists hundreds of types of wall assemblies and assigns to each wall a rating (in hours) of fire resistance. These fire ratings are based on numerous fire tests made at four nationally recognized fire testing laboratories.
The second general method of obtaining fire resistance ratings is by relating fire resistance in hours to the `equivalent thickness’ of a masonry wall. The `equivalent thickness’ is the solid thickness that would be obtained if the same amount of concrete contained in a hollow unit were recast without core holes. Different fire ratings are assigned for the various types of aggregate used in concrete masonry units.
The most complete and up-to-date reference on fire ratings is published by the American Insurance Association (formerly called the National Board of Fire Underwriters), 85 John Street, New York, NY 10038, in their manual entitled FIRE RESISTANCE RATINGS. This manual presents data for the information of building inspectors and other public officials, architects, engineers, and others interested in fire safety in buildings, and types of construction which provide fire resistance ratings of 1, 1-1/2, 2, 2-1/2, 3 and 4 hours, as may be required by codes or regulations. The American Insurance Association is constantly revising and updating this manual as new products and retests are evaluated and published.
Buildings erected for public use in Virginia are regulated by the VIRGINIG FIRE SAFETY REGULATIONS. Assistance in the use of this code may be obtained from the State Fire Marshall, 809 Blanton Building, P.O. Box 1157, Richmond, Virginia 23209, (telephone: 770-3675). Copies of the VIRGINIA FIRE SAFETY REGULATIONS may be obtained from this address free.
Cities and municipalities may have local codes which control their fire regulations and fire ratings. This should be investigated before applying the ratings from the VIRGINIA FIRE SAFETY REGULATIONS.
Following is a good reference for extimating the fire resistance ratings of concrete masonry by the “equivalent thickness” method. This NCCMA TEK 6 contains easy-to-follow instructions and examples. The chart shown on page 2 of this folder uses average fire resistance values derived from various recognized sources and serves as a valuable estimating tool. It is important to remember however, that the chart values are not identical to those values listed in FIRE RESISTANCE RATINGS published by the American Insurance Association (formerly the National Board of Fire Underwriters). The Virginia State Fire Marshall recognizes only the values carried in the FIRE RESISTANCE RATINGS manual or the VIRGINIA FIRE SAFETY REGULATIONS manual.