Page 328 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

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FLOOR AND ROOF SYSTEMS

7.12 CHAPTER SEVEN

7.6 WOOD-FIBER PLANKS

Planks formed of wood fibers bonded with portland cement provide a lightweight roof deck with
insulating and acoustical properties. The typical density of this material ranges between 30 and
3
40 lb/ft . Some plank types have diaphragm capacities. When used as part of an approved ceiling
assembly, many planks can achieve a fire rating. This type of roof deck system is commonly used
for gymnasiums and similar facilities because of its superior acoustical properties.
The planks are usually supported by steel bulb tees (Fig. 7.13), which are nominally spaced 32
to 48 in on center. The joint over the bulb tee is typically grouted with a gypsum-concrete grout and
roofing materials are applied to the top surface of the planks.

7.7 GYPSUM-CONCRETE DECKS

Although they are not in common use today, poured gypsum concrete can be used in conjunction
with steel bulb tees, formboards, and galvanized reinforcing mesh (Fig. 7.14). Drainage slopes can
be readily built into the roof deck by varying the thickness of gypsum.

FIGURE 7.13 (a) Wood-fiber planks from roof deck. (b) Plank is supported by a steel
bulb tee.

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