- Author
- National Bureau of Standards Technical News Bulletin
- Title
- Fire Resistance of Heavy Timber Construction.
- Journal
- Technical News Bulletin (National Bureau of Standards), No. 349, 35-35, May 1946
- Keywords
- timber | construction | fire resistance tests | floors
- Abstract
- Although heavy timber or "mill" construction floors have withstood fires better than lighter unprotected wood construction, no information has been available on how long they withstand fires of the severity used in the standard furnace test. Experiments recently concluded at the Bureau under the direction of S. H. Ingberg show that the limit of resistance of such floors, with the lower face exposed to fire, is determined either by failure under representative working loads or by occurrence of flame or ignition of combustible material on the upper side. With a 1-inch finish floor on top, the fire resistance of laminated floors of 4-inch planks on edge averaged 45 minutes; with 6-inch planks, a little over 1 hour; and with 8-inch planks, about 1 1/2 hours. With the structural portion of the floor of tongued and grooved plank of 3-inch nominal thicknes laid flatwise, the fire resistance was approximately 45 minutes. Impregnation of the wood with fire-retarding chemicals increased the fire resistance of 4-inch floors by about 15 minutes. A comparable increase was obtained with a heavy coating of a fire-retarding compound on the lower surface.