Building Design and Construction Handbook - Merritt - Ventech!

FIGURE 1.6 (Continued)
BUILDING SYSTEMS 1.17
ceiling is suspended below a floor or roof for esthetic or other reasons. Figure 1.6b
shows such a ceiling. It is formed with acoustical panels and incorporates a lighting
fixture and air-conditioning inlets and outlets.
Metal and wood subfloors and beams require fire protection. Figure 1.6c shows
a roof and its steel beams protected on the underside by a sprayed-on mineral fiber.
Figure 1.6d shows a roof and open-web steel joists protected on the underside by
a continuous, suspended, fire-resistant ceiling. As an alternative to encasement in
or shielding by a fire-resistant material, wood may be made fire-resistant by treatment
with a fire-retardant chemical.
Fire Ratings. Tests have been made, usually in conformance with E119, ‘‘Standard
Methods of Tests of Building Construction and Materials,’’ developed by
ASTM, to determine the length of time specific assemblies of materials can withstand
a standard fire, specified in E119. On the basis of test results, each construction
is assigned a fire rating, which gives the time in hours that the assembly can
withstand the fire. Fire ratings for various types of construction may be obtained
from local, state, or model building codes or the ‘‘Fire Resistance Design Manual,’’
published by the Gypsum Association.
Interior Walls and Partitions. Interior space dividers do not have to withstand
such severe conditions as do exterior walls. For instance, they are not exposed to
rain, snow, and solar radiation. Bearing walls, however, must be strong enough to