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ACCOUSTICAL PROPERTIES An important acoustical property of wood is its ability to damp vibrations. Wood has a cellular network of minute interlocking pores which convert sound energy into heat by frictional and viscoelastic resistance. Because of the high internal friction created by the cellular pore network, wood has more sound damping capacity than most structural materials. Floor, ceiling and wall assemblies of wood can provide effective economical sound absorption when properly utilised. Western Red Cedar is particularly effective in this regard and can be used to help reduce noise or confine it to certain areas. FLAME SPREAD RATING Flame spread ratings describe the surface burning characteristics of interior finishes. They are used to regulate the use of interior finish materials to reduce the probability of rapid fire spread. Materials are burned in a test furnace for a relative assessment of flammability. The lower the flame spread rating, the more the material resists the spread of fire. Building codes in North America generally define as 'interior finish' any exposed material that forms part of the building interior. This usually includes interior wall and ceiling finishes, flooring, windows, doors and other wood surfaces. US codes set the maximum flame spread rating for interior wall and ceiling finishes in most buildings at 200. The flame spread rating for Western Red Cedar is 69 (Class II rating). SMOKE DEVELOPMENT RATING Smoke developed classifications reflect the amount of smoke released by a burning material. They are used in conjunction with flame spread ratings to regulate the use of interior finish materials where the potential to generate smoke or control smoke movement is of major fire safety importance.
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