Section 379B Sound Transmission Control

R-9 UCRC Index of Sections

Section 379B SOUND TRANSMISSION CONTROL

Code Plain English

379B.1 General.
Individual JLWQ shall comply with Division IIA of Appendix Chapter 12A as for apartment houses and as provided in this division. Existing buildings being converted to Group R-9 Occupancies are not required to, but, are recommended to consider exterior noise sources pursuant to Section 1208A.8.4.
Exception: In existing buildings, existing walls and floor/ceilings are not required to meet these requirements unless they are opened or altered.

379B.1 General.
In general there are three types of sound issues in buildings.

Sound transmission in general between spaces, such as speech, music, etc..

Impact transmission such as the sound of high heels on a floor is heard below, and

Exterior noise such as traffc, trains and the general din of the environment, which can be measured.

Live/work units must consider and respond to "exterior noise sources". These can be measured with testing equipment and are usually expressed as "CNEL," which means "Community Noise Level". Once measured, in live/work a means must be devised to reduce the CNELlevel down to 45 decibels (dB s). If CNEL is presently 65, then a wall assembly must be devised which cuts the level by 20 decibels, i.e. have an STC rating of 20 or greater. Standard double-glazed windows will achieve a rating of STC 28, for example.
The live/work code clearly states that in the renovation of existing buildings to F-7 work/live occupancy, alterations are recommended but not required to comply with requirements regarding outside noise sources.
In all types of units being created in a conversion of an existing building, requirements for attenuation of exterior noise do not apply to existing walls and floor/ceilings that are not being "opened or altered." As an example, a warehouse conversion to live/work that did not replace exterior single-glazed industrial sash windows would be exempt. If the windows were being replaced, they would be required to have an STC rating that would be capable of reducing measured CNEL to 45.

379B.2 Airborne Sound Insulation.

379B.2.1 General.
Buildings or a portion of buildings classified as Group R-9 Occupancies shall comply with Division IIA of Appendix Chapter 12A as for apartment houses by providing STC 50 walls and floor/ceilings where a designated residential area abuts another occupied area.
Sound Transmission Class (STC) is a numerical designation given tested walls and floor/ceiling assemblies which express the number of decibels by which the assembly will reduce sound levels as perceived from one side of the assembly to the other. STC 50 is the minimum level which must be achieved between all live/work units and between the units and any corridor or interior common spaces. A typical wood stud wall achieving STC might have two layers of 5/8" sheet rock on one side and one layer of the same mounted on resilient channels, a sort of sheet-metal sound-absorbing leaf spring, which are in turn affxed to studs. The whole wall or floor/ceiling assembly gets insulated, caulked around the edge, and inspected.

379B.3 Impact Insulation.

379B.3.1 General.
Buildings or a portion of buildings with individual spaces or JLWQ shall comply with Division IIA of Appendix Chapter 12A as for apartment houses by providing IIC 50 floor/ceilings where a designated residential area abuts another occupied area.
Sound Impact Class (IIC) also is required to meet or exceed a rating of 50. It should be noted that in a building with concrete floor/ceilings, an 8" thick slab will usually not meet IIC 50 without the addition of carpet or an acoustic mat under either a topping slab or a heavy wood floor.

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Section 379B SOUND TRANSMISSION CONTROL
Code	Plain English
379B.1 General. Individual JLWQ shall comply with Division IIA of Appendix Chapter 12A as for apartment houses and as provided in this division. Existing buildings being converted to Group R-9 Occupancies are not required to, but, are recommended to consider exterior noise sources pursuant to Section 1208A.8.4. Exception: In existing buildings, existing walls and floor/ceilings are not required to meet these requirements unless they are opened or altered.	379B.1 General. In general there are three types of sound issues in buildings. Sound transmission in general between spaces, such as speech, music, etc.. Impact transmission such as the sound of high heels on a floor is heard below, and Exterior noise such as traffc, trains and the general din of the environment, which can be measured. Live/work units must consider and respond to "exterior noise sources". These can be measured with testing equipment and are usually expressed as "CNEL," which means "Community Noise Level". Once measured, in live/work a means must be devised to reduce the CNELlevel down to 45 decibels (dB s). If CNEL is presently 65, then a wall assembly must be devised which cuts the level by 20 decibels, i.e. have an STC rating of 20 or greater. Standard double-glazed windows will achieve a rating of STC 28, for example. The live/work code clearly states that in the renovation of existing buildings to F-7 work/live occupancy, alterations are recommended but not required to comply with requirements regarding outside noise sources. In all types of units being created in a conversion of an existing building, requirements for attenuation of exterior noise do not apply to existing walls and floor/ceilings that are not being "opened or altered." As an example, a warehouse conversion to live/work that did not replace exterior single-glazed industrial sash windows would be exempt. If the windows were being replaced, they would be required to have an STC rating that would be capable of reducing measured CNEL to 45.
379B.2 Airborne Sound Insulation. 379B.2.1 General. Buildings or a portion of buildings classified as Group R-9 Occupancies shall comply with Division IIA of Appendix Chapter 12A as for apartment houses by providing STC 50 walls and floor/ceilings where a designated residential area abuts another occupied area.	Sound Transmission Class (STC) is a numerical designation given tested walls and floor/ceiling assemblies which express the number of decibels by which the assembly will reduce sound levels as perceived from one side of the assembly to the other. STC 50 is the minimum level which must be achieved between all live/work units and between the units and any corridor or interior common spaces. A typical wood stud wall achieving STC might have two layers of 5/8" sheet rock on one side and one layer of the same mounted on resilient channels, a sort of sheet-metal sound-absorbing leaf spring, which are in turn affxed to studs. The whole wall or floor/ceiling assembly gets insulated, caulked around the edge, and inspected.
379B.3 Impact Insulation. 379B.3.1 General. Buildings or a portion of buildings with individual spaces or JLWQ shall comply with Division IIA of Appendix Chapter 12A as for apartment houses by providing IIC 50 floor/ceilings where a designated residential area abuts another occupied area.	Sound Impact Class (IIC) also is required to meet or exceed a rating of 50. It should be noted that in a building with concrete floor/ceilings, an 8" thick slab will usually not meet IIC 50 without the addition of carpet or an acoustic mat under either a topping slab or a heavy wood floor.