| FIRE ENDURANCE, SOUND
TRANSMISSION Sound
Transmission
Sound transmission ratings are closely aligned with fire
endurance ratings for assemblies. This is because flame penetration and sound penetration
follow similar paths of least resistance.
Sound striking a wall or ceiling surface is transmitted
through the air in the wall or ceiling cavity. It then strikes the opposite wall surface,
causing it to vibrate and transmit the sound into the adjoining room. Sound also is
transmitted through any openings going into the room, such as air ducts, electrical
outlets, window openings, and doors. This is airborne sound transmission.
The Sound Transmission Class (STC) method of rating
airborne sounds evaluates the comfortability of a particular living space. The higher the
STC, the better the airborne noise control performance of the structure. An STC of 50 or
above is generally considered a good airborne noise control rating. The following table
describes the privacy from each STC rating:
| STC
Rating |
Privacy Afforded |
|
| 25 |
Normal speech easily
understood |
| 30 |
Normal speech audible but not
intelligible |
| 35 |
Loud speech audible and fairly
understandable |
| 40 |
Loud speech barely audible but
not intelligible |
| 45 |
Loud speech barely audible |
| 50 |
Shouting barely audible |
| 55 |
Shouting not audible |
Flame Spread
Flame spread ratings are often confused with fire endurance
ratings. Flame spread is solely a measure of the surface burning characteristics of a
material. A low flame spread material will not necessarily improve the performance of a
fire endurance assembly.
Flame spread requirements are typically used by the code
for interior finish materials. Different maximum flame spread rates are permitted
depending upon the building occupancy, location of the material in the
building, and the presence o sprinklers. In certain cases within the code, wood structural
members with a Class A flame spread rating can be treated as non-combustible material.
Generally, the building code flame spread classifications
are:
| Flame
Spread |
| Class |
Range |
Locations |
| I or A |
0-25 |
Enclosed
vertical exits |
| II or B |
26-75 |
Exit access
corridors |
| III or C |
76-200 |
Other rooms and
areas |
Southern Pine paneling and lumber thicker than
1/4" fits into the Class C flame spread range. Southern Pine has a flame spread
rating of 130-195 based on the ASTM E 84 test method according to Underwriter's
Laboratory, UL 527, May 1971, Test Report 64S197.
For additional information, see Flame Spread Performance of
Wood Products, Design for Code Acceptance No.1, from the American Forest & Paper
Association.
Smoke Developed Index
A Smoke Developed Index was also measured for various wood
products. This Index has a value of 100 for Red Oak. in none of the products tested did
the Smoke Developed Index exceed 450, a limiting value used in building code regulations.
SOUTHERN PINE SPECIFICATION
GUIDELINES
These guidelines are intended to assist in specifying the
most economical and efficient use of Southern Pine lumber products. They should also help
minimize misunderstandings between specifier and supplier. Product availability and
economy varies by market area. Becoming familiar with the products available in your area
will allow you to more easily obtain materials to satisfy your demands, Both the Southern
Forest Products Association and the Southeastern Lumber Manufacturers Association maintain
publications listing member mills and products they produce. In addition, SFPA's Regional
Market managers are available for local assistance.
Identification and Quality Control - Each piece of lumber
should be grademarked by an agency accredited by the American Lumber Standard Committee
(ALSC), and manufactured in accordance with Product Standard PS 20-94 published by the
U.S. Department of Commerce.
Two Typical Lumber Grade Marks
Product Classification - Products
should be identified by manufactured categories such as Dimension, Structural Light
Framing, Decking, Boards, Timbers, etc. Products in categories such as Finish, Flooring,
Ceiling, and Siding, etc., should include the pattern name and number assigned by the
ruleswriting agency. This will correctly identify the product and ensure that it conforms
to standard. Select from the grade descriptions on pages 3-6.
Size and Length of Pieces -
Products included in lumber standards, such as Dimension Lumber, should be specified by
nominal sizes for thickness and width, and by common lengths which are 8' to 20' in 2'
increments. Products with patterns and special orders should include the desired net, dry
size, plus the dimensioned profile pattern for less common items. Standard sizes are
listed on page 7. |
