This topic came up in discussion with a customer who wanted to install more outlets in an apartment that is to undergo a gut renovation, but had problems with noise transmission between it and the adjoining apartment. They would like to try to improve the old situation, not leave it the same or worse.
How much do you think putting outlet boxes into the wall affects the overall noise level that a wall allows through? These walls are 2x4 wood with 5/8 gyp board one side and whatever winds up going on the renovated side. Batt insulation will be used in the renovation that was not there before and any boxes could be caulked in of course.
Re: Outlets in Party Walls OK, Not OK, or Not Advisable?#52723 06/03/0501:20 PM06/03/0501:20 PM
From Volume One of the UL Fire Resistance Directory.
WALL AND PARTITION ASSEMBLIES
Metallic Eletrical Outlet Boxes
Listed single and double gang metallic outlet and switch boxes with metallic or nonmetalliccover plates may be used in bearing and nonbearing wood stud and steel stud walls with ratings not exceeding 2h. These walls shall have gypsum wallboard facings similar to those shown in Design Nos. U301,U411, and U425. The metallic outlet or switch boxes shall be securely fastened to the studs and the opening in the wallboard facing shall be cut so that the clearance between the box and the wallboard does not exceed 1/8 in. The surface area of individual metallic outlet or switch boxes shall not exceed 16 sq in. The aggregate surface area of the boxes shall not exceed 100 sq in per 100 sq ft of wall surface.
Metallic boxes located on opposite sides of walls or partitions shall be seperated by a minimum horizontal distance of 24in. This minimum seperation distance between metallic boxes may be reduced when "Wall Opening Protective Materials" (CLIV) are installed according to the requirements of their Classification.
Metallic boxes shall not be installed on opposite side of walls or partitions of staggered stud construction unless "Wall Opening Protective Materials" are installed according to the requirements of their Classification.
AC, sound proofing is another issue, make sure the batting is not thick enough to have to be compressed between the sheetrock or it will transmit noise just about as well as having none at all.
[This message has been edited by Roger (edited 06-03-2005).]
Re: Outlets in Party Walls OK, Not OK, or Not Advisable?#52724 06/03/0501:57 PM06/03/0501:57 PM
Good info about considerations for outlets on both sides of a wall, Roger.
Staggered studs was being considered to be added for it's enhanced sound reducing qualities. Could you advise what the "Wall opening protective materials" would be in such an installation, or where that is detailed? Thanks.
Re: Outlets in Party Walls OK, Not OK, or Not Advisable?#52725 06/03/0502:08 PM06/03/0502:08 PM
Typical party-wall construction for townhouses, where the party-wall is on the property line, is two layers of 1" type X drywall panels, each 24" wide and 8' high, with metal tracks to hold it together. This provides a 2-hour fire rating.
The metal tracks are attached to the framing of the adjacent interior wall with metal clips that will melt in the event of a fire, allowing the adjacent structure to burn completely down without pulling down the party wall.
With this type of construction, an outlet installed in a party wall isn't actually in the party wall. It's between the interior drywall and the party wall.
For an apartment, I would think that what you'd have would be a regular firewall, not a party wall.
Re: Outlets in Party Walls OK, Not OK, or Not Advisable?#52726 06/03/0504:29 PM06/03/0504:29 PM
300.21 Spread of Fire or Products of Combustion Electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations through fire-resistant–rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating.
FPN: Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made. Building codes also contain restrictions on membrane penetrations on opposite sides of a fire-resistance–rated wall assembly. An example is the 600-mm (24-in.) minimum horizontal separation that usually applies between boxes installed on opposite sides of the wall. Assistance in complying with 300.21 can be found in building codes, fire resistance directories, and product listings.
Joe Tedesco, NEC Consultant
Re: Outlets in Party Walls OK, Not OK, or Not Advisable?#52727 06/03/0507:37 PM06/03/0507:37 PM
So it appears that sound is more the issue... Just so happens Fire Wall type assembly is best result for effect. Staggered stud bays, minimum opening, full insulation, thicker rock, and fire padded boxes. Add a hat channel to framing before rock to further minimize vibration... One step above that would be to build two walls seperate from eachother.