Sound insulation between apartments

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Sound insulation between apartments

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Ser

N A ~

110 ~ 2 1 h 8

no.

19

c .

2 NATIONAL RESEARCH COUNCIL

CANADA

DIVISION OF BUILDING RESEARCH

HOUSING NOTE NO. 19

I

_&*D.

f . - , + - 5 r A s c % , r,-I , , 4 r , ,

I

-.

by

T. D. NORTHWOOD AND A. C. VEALE

REPRINTED FROM

CANADIAN BUILDER, VOL. XIV, NO.

8 AUGUST

1964, P.30

OTTAWA, AUGUST

1964

This Note may be reprinted without ame~dment provided acknowledgement is given to Canadian Builder.

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DINING

LIVING

ROOM

KITCHEN

FOYER

BEDROOM

F I G U R E 1

P O O R L Y P L A N N E D B U I L D I N G

C h o i c e s t S p a c e i s O c c u p i e d b y

N o n - C r i t i c a l A r e a s . B e d r o o m

i s A d j a c e n t t o E l e v a t o r a n d t o

N e i g h b o u r s ' K i t c h e n .

F I G U R E 2

WELL P L A N N E D B U l L D l N G

N o n - C r i t i c a l A r e a s A c t a s

B u f f e r s A g a i n s t U n w a n t e d

N o i s e .

Sound iinsullatiion between apartments

A

most serious drawback of apart-

ment living is the transmission of noise t o and f r o m the neighbors. T h e purpose of this paper is to consider what is needed and what can be done to provide adequate sound insulation between apartments and other attached dwellings.

Sound Insulation ratings

Since there is considerable variety in methods of rating the performance of partitions it will be useful to define the ones that will be used here. The first step is to subdivide the problem into the insulation of airborne sounds (such as voices and radios) and impact sounds (such as footsteps).

Airborne sound insulation was forrn- erly specified in terms of the sound transmission loss (TL) in decibels, av- eraged over a specified series of test

frequencies, but the averaging procedure was often not spelled out carefully enough to ensure that the figures quoted were comparable. This and other defects have led to the use of a new performance fig-

This is the second of two articles on noise control within and between

dwellings. The first, dealing with

noise control within dwellings, ap- peared in the July issue of Canadian Builder and has since been reprinted by the Division of Building Research, National Research Council as Housing

Note No. 18. Joint authors of this

second article dealing with sound in- sulation between apartments are T. D. Northwood, Head, Physics Section, D.B.R., and A. C. Veale, Research Of- ficer, Housing Section, D.B.R.

ure, the Sound Transmission Class (STC), which is designed specifically to rate separations between the kinds of noise that are common in dwelling. Numerical- ly, the STC is approximately the same as the traditional nine-frequency average, but it protects against weaknesses of a type often encountered in lightweight construction.

There is as yet no standard procedure for rating the impact performance of floors, but use will be made here of a tentative procedure developed by the In- ternational Organization for Standardi- zation and now being examined by the U.S. Federal Housing Administration. FHA Bulletin No. 750, "Impact Noisc Control in Multifamily Dwellings," pub- lished in January 1963, lists Impact Noise Ratings (INR) for a number of floor constructions.

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How Much Sound Insulation Is Neeaed? It is meaningless to talk of an apartment building being "soundproof" in any absolute sense. Rather it is necessary to decide on some arbitrary compromise between cost and tenant satisfaction. Fortunately it is possible without tre- mendous expenditure to reduce intrud- ing noises to the point where most tenants will be satisfied most of the time. The direct and obvious procedure for determining what constitutes adequate sound insulation is to canvass the tenants of many buildings, and at the same time make insulation measurements in the buildings. To do this properly is a major task, but it has been done in

several European countries. Results of a

British survey showed that 40% of ten-

ants separated by partitions rated at

STC 45 were disturbed by noise, and

about 30% were willing to pay more

rent for more sound insulation. For STC

50 partitions the corresponding figures

were 25 and 15%.

It is recommended, therefore, that all party walls and floors should have an airborne sound insulation value of STC

50 and that floors should have, in addi-

tion, an Impact Noise Rating (INR) of

0 decibels. These recommendations for

walls and floors are intended to ensure that noise from the neighbours will cause only minor disturbance. The impact recommendation is the same as that of the U.S. Federal Housing Admini- stration. Some wall and floor constructions that meet these recommended

standards are listed in Tables A and C.

A slightly lower standard of sound insulation may be necessary in economy housing, but the minimum standard that

should be allowed is STC 45 (airborne

sound insulation) for party walls and floors and INR (impact noise insulation)

of -10 dB (10 decibles poorer than INR

of 0 dB) for floors. These minimum

standards may result in some disturbance for nearly half of the tenants. The mini-

mum of STC 45 corresponds to the

minimum requirement for airborne

noise insulation for walls and floors as prescribed in the "Housing Standards". Some wall and floor constructions that meet these minimum standards are list-

ed in Tables B and D.

Building Layout

Much can be done with the layout of apartments to minimize the transfer of noise in the more critical areas (bed- rooms and living rooms). The common apartment building pattern is a stack of identical units forming successive storeys

of a building. Usually the layout of an

individual floor can be so planned that the critical rooms are separated from adjacent apartments by buffer areas (closets, foyers, and kitchens). If this

88 Ib. per

so. :I. nr more

,-Resilient clips

A. 1 A. 4 A. 5

Single Masonry Wall Wood Stud Wall Staggered Stud Wall

-

Rnuuh and finish lloors - , -Concrete screed, 20 Ib. per sq. ft.

, '

-

_i_{i n , sofi fibre board}

-

_{Glass fibre quilt or foamed plastic7}

- . . -+- - . . _{- .} _. I' . - . -. ' I < : I a : , , rrrmr+r+m

.

f . . ' . . * Concrete slab - 50 Ib. per sq. ft.

-- 518 in. gypsum wallboard , .-- :

b.,.''

f in. gypsum lath

Resilient clips

-

I _lin. sanded gypsum plaster

C. 1 C. 4 C. 7

Floating Floor o n Floating Wood Floor Floating Concrete Screed Concrete Slab on Steel Joists

F I G U R E . 3

S O M E W A L L A N D F L O O R C O N S T R U C T I O N S W H I C H M E E T R E C O M M E N D E D S O U N D I N S U L A T I O N S T A N D A R D S ( S e e T a b l e s A t o D f o r F u r t h e r D e t a i l s )

-

is done, an STC 45 party wall may be

adequate. Where this arrangement is not possible, the next best thing is to place relatively quiet regions, such as bed- rooms, adjacent to each other, and to

provide an STC 50 party wall between

them. The worst possible arrangement is to place critical regions of one unit adjacent to noisy regions of the next

unit (a kitchen next to the neighbours

bedroom, for example); here even an

STC 50 wall will be inadequate. Figures

1 and 2 show examples of poor and

good planning.

Kitchens and bathrooms are non- critical regions, as far as the reception of noise is concerned, but plumbing fixtures are often troublesome sources of noise. Moreover, the service pipes may provide an extra transmission path between apartments. To minimize the problem, quiet fixtures should be used; kitchens and bathrooms of adjacent units should be placed back to back, with services in a wall away from the critical rooms; pipes should be padded at supporting points, and where they pass

through the walls a resilient gasket

should be used to seal the holes. Similar care should be taken to avoid air leaks around heating and electrical outlets.

Public corridors and stairs may be useful buffers between apartments or they may themselves be noise sources. If they are to act as noise buffers, the walls or ceiling should be finished in sound absorbing material, and a soft floor covering should be used; apartment doors should not face each other across the corridor; and a refrigerator- type gasket around the door frame is helpful both in reducing the leakage of sound and softening the impacts of slam- ming doors.

Elevators constitute a special prob-

lem since they may cause noise or vibration throughout the whole building. The frequent practice of surrounding them with stairways and corridors is a good one, but where possible it is desirable to make a structural break between this section of the structure and the residential sections. The hoisting machinery should of course be properly isolated.

Party Wall and Floor Construction The traditional way of securing satis- factory sound insulation, especially for airborne sound, was to use massive con-

struction. In a homogeneous wall or

floor, about 36 Ib per sq ft are needed

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about 80 Ib per sq ft to obtain STC 50. These weight requirements are, however, not easily incorporated in modern construction.

The alternative to a massive wall is one consisting of several more or less independent layers. This is the approach that is compatible with modern building

design. Moreover, it is the only

approach to the problem of impact transmission through floors. The major problem is to guard against short-cir- cuiting of the individual layers by air leaks or by bridging connections introduced at construction joints.

In masonry construction, the single massive wall may be replaced by a cavity wall consisting of two independent wythes (with flexible cross-ties). The STC 50 requirement may be met by two wythes, each weighing about 25 Ib per sq ft and separated by an air space. Alternatively, it may be met by one such wythe with lath and plaster supported by resilient clips on one side.

The sound insulation of a con-

ventional stud wall may be improved by supporting the lath and plaster on resilient mountings or by using two sets of studs, slightly offset, to support the two surfaces independently. When such a discontinuity is introduced between surfaces, the addition of mineral wool or glass fibre batts or blankets in the stud space is worthwhile; in the conventional stud wall it is of limited value.

The principle of discontinuous construction applies equally to floor designs. The additional problem of impact is most readily solved by a floating floor

construction. An lnaependently or resil- iently supported ceiling is nearly as ef- fective, but once the vibration enters the structure there is danger that it may be propagated for somc distance and into flanking walls.

Special Problems

Apart from the noise people make, there are generally a few mechanical noise sources that need attention. Ele- vators have already been discussed. Other possible problems arise in the machinery associated with heating, hot water circulation, and ventilation. Re- cognized mounting procedures are avail- able for isolating the vibrations of such machines from the building structure. A problem peculiar to heating plants may be a low-frequency roar of com- bustion, and therefore, apartment units in the immediate vicinity of the furnace room should be given special attention. This is one region where massive walls and floors, desirable for other reasons such as fire protection, may be the best solution.

Precautions During Construction

Unfortunately, construction defects

that are significant from the viewpoint of noise are not always of a type that catch the eye of an inspector. He should be specially instructed to guard against small cracks or leaks, for example, around service pipes, that may nullify an otherwise excellent party wall. The advantage of a resilient clamping system for supporting pipes may be lost by let- ting the pipes bear against a wall sur- face. Floating floors, cavity walls, and similar systems that depend on a struc-

tural discontinuity require special attention to ensure that they are not spoiled by accumulated debris or perhaps by extra "bracing" added by a well-meaning carpenter. "Floating" floors must not be nailed through the resilient layer to the underlying structure.

Summary and

Recommendations

To exclude the neighbours' noises from attached dwelling, builders should:

a)-Properly plan the layout of the

building and the individual dwellings within it.

b)--Choose wall and floor separations with the required sound insulation values,

c)-Make sure that the separations are

constructed as specified.

d)-Make sure that there are no easy

paths for sound to travel around the edges of the separations. A selection of wall and floor constructions which meet either the recommended or the minimum sound insula-

tion standards are listed in Tables A to

D. These constructions will also have the one hour of fire resistance usually required for separations between dwelling units, provided that approved ma- terials and installation details are used. Details on fire-resistive constructions are contained in Fire Resistance Ratings, 1961 (to be revised and expanded in 1965), which is Supplement No. 2 of the National Building Code of Canada, or in Housing Standards, Canada,

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TABLE A

SOME TYPICAL WALLS WHICH MEET RECOMMENDED SOUND INSULATION S T A N D A R D S S T C 50 OR BETTER

A-1 Single masonry wall*

-

weight at least 80 Ib per sq ft including plaster, if any (Figure 3).

A-2 Masonry cavity wall

-

2 wythes of masonry* spaced at least 2 in. apart, each wythe weighing at least 20 Ib per sq ft; wythes tied to- gether with butterfly ties at 2-ft centres.

A-3 Composite masonry wall

-

basic wall of masonry* weighing at least 22 Ib per sq ft; on one side of basic wall an additional wythe consisting of %-in. gypsum lath mounted with resilient clips, and j/4 -in. sanded gypsum plaster. A-4 Wood stud wall

-

2- by 4-in.

studs; on each face %-in. gypsum lath mounted with resilient clips, %-in sanded gypsum plaster, min- era1 or glass wool batts between studs (Figure 3).

A-5 Staggered stud wall

-

2- by 3- in. studs at 16-in. centres on common 2- by 6-in. plate; on each face %-in. gypsum lath, %-in. sanded gypsum plaster; mineral or glass wool batts between one set of studs (Figure 3).

TABLE B

SOME TYPICAL WALLS WHICH MEET MINIMUM SOUND INSUL- ATION STANDARDS

-

STC 45 OR BETTER

B-1 _{Single masonry wall*}

-

_weight

more than 36 Ib per sq ft including plaster, if any.

B-2 Composite masonry wall

-

basic wall of masonry* weighing at least 22 Ib per sq ft; on one side of basic wall: furring strips, %-in. gypsum lath, %-in. sanded gypsum plaster.

B-3 Staggered stud wall

-

2- by 4- in. studs on common 2- by 6-in. plate; on each face %-in. sanded gypsum plaster on 3/8-in. gypsum lath. (A variety of alternate sur- face finishes are listed in the Hous- ing Standards.)

B-4 Staggered stud wall

-

2- by 4- in. studs on common 2- by 6-in. plate; mineral or glass wool batts between studs on each face 2 layers of 3/8-in. gypsum wallboard with joints staggered.

*

If porous blocks are used, one face of each block section must be sealed with plaster or heavy paint.

Sound Rnsullatiion for

floors and wallls

TABLE C

SOME TYPICAL FLOORS WHICH MEET RECOMMENDED SOUND INSULATION STANDARDS

-

STC 50 OR BETTER (AIRBORNE NOISE) AND INR 0 dB OR BETTER (IMPACT NOISE)

C-1 Floating floor on concrete slab- 4-in. solid concrete or equivalent slab weighing at least 50 Ib. per sq ft.; ceiling-side bare or plastered directly on slab; floor-side wood furring strips on %-in. soft fibreboard (either in strips or a complete layer), rough and finish floors (Figure 3).

C-2 Floating screed on concrete s l a b - same as above except floor-side 1-in. foamed plastic or paper-covered glass fibre quilt, supporting 2-in. mesh re- inforced concrete screed.

C-3 Carpeted concrete slab-6-in. concrete slab weighing at least 70 Ib. per sq ft.; ceiling-side plastered; floor-side carpeted (pad beneath carpet will give outstanding impact resistance). C-4 Floating wood floor-wood joists 16

in. on centres; mineral or glass wool batts between joists; on ceiling-side %-in. gypsum wallboard** on furring strips on resilient clips; on floor-side wood subfloor, %-in. soft fibreboard, furring strips, rough and finish floors (Figure 3).

C-5 Floating wood floor-same as C-4 except that ceiling is on separate ceiling joists supported at walls.

C-6 Carpeted wood floor-same as C-4 except that floor-side consists only of wood subfloor and carpet of not less than 7 oz. weight per sq ft. (pad under carpet will give outstanding impact resistance).

C-7 Floating concrete screed o n steel joist+open steel joists or similar structure; on ceiling-side Yz-in. gypsum lath on resilient clips, M-in. sanded gypsum plaster; on floor-side formwork, paper-covered glass fibre quilt or foamed plastic, concrete screed weighing at least 20 Ib. per sq. ft. (Figure 3).

C-8 Carpeted concrete screed on wood joists-wood joists on 16-in. centres; on ceiling-side %-in. gypsum wallboard;** on floor-side formwork, concrete screed weighing at least 20 Ib. per sq. ft., carpet on sponge rubber pad. "*%-in. special fire-retardant gypsum board listed by Underwriters Laborator- ies, Inc. needed for 1-hr. fire resistance.

TABLE

D

SOME TYPICAL FLOORS WHICH MEET MINIMUM SOUND INSULATION S T A N D A R D S S T C 45 OR BETTER (AIRBORNE NOISE) and INR -10 dB OR BETTER (IMPACT NOISE)

D-1 Concrete slab with suspended ceil- clips; on floor side wooden subfloor i n g 4 - i n . solid concrete or equivalent and finish floor.

slab weighing at least 50 lb. per sq D-5 Wood floor with separate ceiling- ft.; ceiling-side %-in. gypsum lath same as D-4 except that ceiling is on on resilient clips, %-in. sanded gypsum separate joists supported at walls. plaster; floor side parquet, linoleum, D-6 Concrete slab on steel joists- or vinyl tile. 2%-in. dense concrete slab on form- D-2

concrete

slab with independent ceil. work on steel joists; on ceiling-side % -

ing-same as D-1 except that ceiling in. sanded gypsum plaster on metal mounted on separate joists supported lath wired to joist bottoms; on floor- at walls. side wood parquet, linoleum, or vinyl

tile.

D-3 Floating wood floor-wood joists _{D.7 Concrete slab}_{on steel joist-same} 16 in. on centres; on ceiling-side %- _as _{except that ceiling has resilient} in. gypsum wallboard**; on floor-side _{,-lips or resilient furring strips wired} wood subfloor, %-in. soft fibreboard, _{to joist bottoms, %-in. gypsum wall-} furring strips, rough and finish floors. _{board**; plus mineral}_{or glass wool} D-4 Wood floor with suspended ceiling batts between joists.

-wood joists 16 in. on centres; min- **%-in. special fire-retardant gypsum era1 or glass wool batts between joists; board listed by Underwriters Labora- on ceiling side %-in. gypsum wall- tories, Inc. needed for I-hr. fire resist- board** on furring strips on resilient ance.