leaving the opposite side of the structural surface. Sound
transmission class (STC) is the rating used to characterize
airborne noise insulation. A wall system with a high STC
rating is effective in preventing the transmission of sound.
Table 17–1 lists the STC ratings for several types of wall
systems; detailed information for both wall and floor are
given in FPL–GTR–43 (Rudder 1985).
Impact noise insulation is the resistance to noise generated
by footsteps or dropping objects, generally addressed at
floor–ceiling assemblies in multi-family dwellings. Impact
insulation class (IIC) is the rating used to characterize the
impact noise insulation of an assembly. Both the character
of the flooring material and the structural details of the floor
influence the IIC rating. Additional information on IIC rat-
ings for wood construction is given in FPL–GTR–59 (Sher-
wood and Moody 1989).
Literature Cited
AF&PA. 2001. Wood frame construction manual for
one- and two-family dwellings, 2001 edition. Washington,
DC: American Forest & Paper Association.
AF&PA. 2005a. National design specification for wood
construction. Washington, DC: American Forest & Paper
Association.
AF&PA. 2005b. Span tables for joists and rafters.
Washington, DC: American Forest & Paper Association.
AF&PA. 2007. Permanent wood foundation design
specification. Washington, DC: American Forest & Paper
Association.
AITC. 2004. Timber construction manual, 5th edition.
American Institute of Timber Construction. New York:
John Wiley & Sons, Inc.
APA. 2007. Engineered wood construction guide: floor con-
struction. Section 2, Form E30. September 2007. Tacoma,
WA: APA–The Engineered Wood Association.
ASHRAE. 2005. Handbook of fundamentals. Atlanta,
GA: American Society of Heating, Refrigerating and
Air-Conditioning Engineers.
ASTM. 2008. Standard guide for limiting water-induced
damage to buildings. ASTM E241-08. West Conshohocken,
PA: American Society for Testing and Materials.
ASTM. 2009. Standard methods for establishing stress
grades for structural members used in log buildings. ASTM
D3957-09. West Conshohocken, PA: American Society for
Testing and Materials.
AWC. 2009. Prescriptive wood deck construction guide.
Washington, DC: American Wood Council.
Christian, J.E. 1994. Moisture sources. Chapter 8 in mois-
ture control in buildings, ASTM MNL18 (ISBN 0-8031-
2051-6). Philadelphia, PA. American Society for Testing
and Materials.
Faller, R.K.; Ritter, M.A.; Rosson, B.T.; Duwadi, S.R. 1999.
Railing systems for use on timber deck bridges. Under-
ground and other structural design issues. Washington,
D.C.: National Academy Press. Transportation research
record 1656. pp. 110–119.Table 17–1. Sound transmission class (STC) ratings for typical wood-frame walls
STC
rating Privacy afforded Wall structure
25 Normal speech easily understood 6-mm (1/4-in.) wood panels nailed on each side of standard 38- by 89-mm
(nominal 2- by 4-in.) studs.
30 Normal speech audible but not
intelligible9.5-mm (3/8-in.) gypsum wallboard nailed to one side of standard 38- by
89-mm (nominal 2- by 4-in.) studs.
35 Loud speech audible and fairly
understandable20-mm (5/8-in.) gypsum wallboard nailed to both sides of standard 38- by
89-mm (nominal 2- by 4-in.) studs.
40 Loud speech audible but not
intelligibleTwo layers of 20-mm (5/8-in.) gypsum wallboard nailed to both sides of
standard 38- by 89-mm (nominal 2- by 4-in.) studs.
45 Loud speech barely audible Two sets of standard 38- by 64-mm (nominal 2- by 3-in.) studs staggered 0.2 m
(8 in.) on centers fastened by standard 38- by 89-mm (nominal 2- by 4-in.) base
and head plates with two layers of 20-mm (5/8-in.) gypsum wallboard nailed on
the outer edge of each set of studs.
50 Shouting barely audible Standard 38- by 89-mm (nominal 2- by 4-in.) wood studs with resilient channels
nailed horizontally to both sides with 20-mm (5/8-in.) gypsum wallboard
screwed to channels on each side.
55 Shouting not audible Double row of standard 38- by 89-mm (nominal 2- by 4-in.) studs 0.4 m (16 in.)
on centers fastened to separate plates spaced 25 mm (1 in.) apart. Two layers of
20-mm (5/8-in.) gypsum wallboard screwed 0.3 m (12 in.) on center to the
studs. An 89-mm- (3.5-in.-) thick sound-attenuation blanket installed in one stud
cavity.General Technical Report FPL–GTR– 190