Light Steel Framing

?i 446

Acoustic Performance of
Light Steel Framed Systems
Meeting the new requirements of Part E of the
Technical Information Sheet
Building Regulations (2003)
External brickwork fixed to steel structure
using proprietary stainless steel fixings

Insulation
Cavity fire barrier

Light steel studs

Cement particle Plasterboard

board as an on external wall
alternative floor
Acoustic
insulation

M T Gorgolewski
BSc MSc PhD Dip Arch
G H Couchman
18 mm T & G chipboard
MA PhD CEng, MICE

19 mm plasterboard

Resilient strip
Light steel between floor finish
channel and wall lining
Light steel
rail Flexible sealant in gap
between plasterboard
Light steel Z and floor base
edge support
25 - 30 mm resilient layer
of dense mineral wool
Plywood, chipboard (200 kg/m³)
or OSB floor base
Mineral wool
Additional acoustic INSIDE
mineral wool insulation
insulation between around floor edge
the joists Light steel floor joist
(min. 150 mm deep) Resilient bars
Introduction to light
2
Typical isometric view of light steel wall and floor joists steel framing

• Acoustic performance is increasing in importance in residential buildings Acoustic design of

as developers and occupants demand higher standards. lightweight 3
construction
• Amendments to Part E of the Building Regulations came into effect in
July 2003. The new Regulations set more demanding requirements for
the design of separating walls and floors between dwellings. This Requirements of
Technical Information Sheet sets out how the requirements can be Part E of the Building 4
satisfied in light steel framing. Regulations
• Light steel framing offers an efficient and effective way of constructing
walls and floors with good acoustic performance. Walls 5
• Light steel framing relies on the use of layers of mass with minimal rigid
connections between them to achieve good acoustic performance.
Floors 7
• There are a variety of solutions for separating walls and floors that have
repeatedly shown good performance when tested on site.
• For good acoustic performance in any construction, appropriate site Flanking transmission 9
practices are essential to ensure that details are correctly constructed,
and that no unnecessary air paths are created through a wall or floor.
Service penetrations 11
• The detailing of junctions between separating walls, separating floors
and external walls is important to avoid flanking sound transmission.

1
Acoustic performance of light steel framed systems

Introduction to light steel framing

Steel construction is increasingly being used in Thermal performance

residential apartment buildings and mixed-use Modern light steel frame construction in the UK
developments where the benefits of speed, quality and incorporates a significant proportion of the insulation on
off-site prefabrication are important. the outside of the steel frame, leading to a ‘warm frame’
Steel is a quality assured, accurate, high strength, long construction. This reduces the thermal bridging of the
life, adaptable, recycled and recyclable material, steel elements, minimising the risk of cold spots occurring
manufactured to tight specifications. It does not suffer on the internal surface of the wall. It also maintains the
from twisting, warping or movement due to changes in steel above the dew point temperature, avoiding
moisture content. This results in easier fixing of linings interstitial condensation. Light steel framed buildings can
and higher quality finishes, avoiding problems such as readily meet and exceed the standards in Part L (2002) of
cracking around door architraves and skirtings, both the Building Regulations, and Robust Details are available
initially and throughout the life of the building. to address the issues of thermal bridges at junctions.

Structure Claddings
Light steel frames typically comprise C and Z shaped, Light steel framing is suitable for use with a variety of
galvanized cold-formed steel sections, usually 0.9 mm claddings. For a traditional finish, an external leaf of
to 3.2 mm thick, produced by roll forming. For walls, brickwork (or other masonry finish) with a 50 mm clear
C-sections are generally 75 mm to 150 mm deep, at cavity is used. The brickwork is tied back to the light steel
600 mm centres. Where necessary, back to back structure using stainless steel wall ties located in vertical
sections can be used for strengthening. For floors, runners, fixed back to the light steel studs through
150 mm to 300 mm deep C-sections can typically insulation which is placed on the outside of the studs
span from 4 m to 6 m. These sections can also be (Figure 1).
fabricated into longer span trusses. On site, Alternatively, a variety of other claddings can be used,
connections between the light steel elements may be such as render, metal cladding, T&G timber boarding or
made by self drilling, self tapping screws or bolts. In tiling.
the factory, rivets and welding are also used.
2 layers of plasterboard
Useable roof spaces and clear span internal spaces can
be easily created without the need for internal load
bearing walls, allowing for future adaptability and Light steel studs with
mineral wool between
change of use.
Insulated sheathing
Alternative construction methods include: board

• Individual light steel components, assembled on site

(stick build).
• Panels or sub-frames prefabricated in a factory and
assembled together on site to create whole building
structures (panel construction).
• Volumetric production of whole rooms with internal Wall ties in channels
finishes and services fitted in the factory (modular fixed to steel structure
through insulation
construction). Brick external cladding

Fire resistance
Fire resistance is achieved by the use of gypsum lining Figure 1 Typical external wall detail
boards such as plasterboard or gypsum fibreboard.
Foundations
Generally, one layer of fire resistant plasterboard can
achieve 30 minutes fire resistance, suitable for internal Light steel framing can be located on a variety of
walls and envelope walls within individual dwellings. foundations. Strip or trench footings are most commonly
Two layers of plasterboard can achieve 60 minutes fire used, with suitable levelling and locating devices to
resistance, for separating walls and the ceilings of achieve the tighter tolerances for attaching the steel
separating floors. Higher levels of fire resistance can be components. Mini-pile foundations are particularly suited
achieved with additional or thicker layers. Plasterboard for poor ground conditions and can achieve high levels of
linings are attached using bugle-headed self-drilling accuracy for line and level. The light steel framing is fixed
self-tapping screws to minimise the risk of popping of through the bottom track to the concrete, or is restrained
the fixings. by straps fixed to the studs and concrete footings.

2
 <'i'jj,

Acoustic design of lightweight construction

Lightweight constructions achieve very good acoustic Lightweight construction uses dry assembly processes.
performance using the following basic features of Thus, it is important to ensure efficient sealing of possible
design: air paths, which can otherwise lead to local sound transfer.
• Several layers of mass provided by board materials
Low frequency sound
such as plasterboard and chipboard
• Maximum structural separation between layers The sound insulation properties of walls or floors vary with
the frequency of the noise. Generally, high frequencies are
• Decoupling of the structure as far as possible, likely to be attenuated (reduced) more effectively than low
using resilient bars and resilient layers frequencies. This gives the typical frequency curve shown
• Mineral quilt within spaces in Figure 3. This curve is used to arrive at the single figure
acoustic rating quote in the Building Regulations (DnT,w).
• Sealed air paths through the construction
Light steel frame construction uses multiple layer 80

Standardised Level Difference DnT (dB)

constructions with minimal rigid connection between
70
them, and with absorbent materials within the cavities
between layers. 60

Figure 2 illustrates the importance of acoustic 50

separation. Two single skin walls with relatively poor
40
acoustic performance can be brought very close
together and the overall acoustic insulation will be 30
equivalent to roughly the sum of the insulation of the Typical LSF separating floor
two walls. If however they are brought into contact 20
Reference curve for DnT,w =63 dB
with each other such that there are rigid connections,
10
the acoustic performance drops considerably.
0
Thus, in light steel frame separating walls, a double
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
leaf construction is usually used with a cavity
between and minimum structural connection across it. Frequency (Hz)
The two layers act to a large extent as two
independent walls, minimising the transfer of sound Figure 3 Graph of the airborne sound insulation of a
vibration across the structure. Mineral wool is used light steel frame separating floor in one third
within the construction to act as an absorbent layer. octave bands
As a result, acoustic insulation is nearly double that of
each single stud construction. The gap between the To maximise the benefit of double leaf construction, it is
two rows of studs can be as little as 25 mm. important that the cavity is sufficiently wide that the
frequency at which performance diminishes is below the
Separating floors use board materials interspaced with frequency range where the source of noise has most energy.
resilient layers to achieve maximum decoupling and It is generally recommended that a distance of 200 mm is
minimise transfer of sound vibration. Resilient bars are maintained between the plasterboard layers in adjacent
used to connect the ceiling plasterboard to the light rooms.
steel joists. These reduce the rigidity of the
connection and so reduce sound vibration transfer
between the structure and plasterboard lining.

Approximately
30 dB 30 dB 60 dB 36 dB

200 mm

Figure 2 Schematic showing the principle of double layer construction with associated acoustic benefits

3
Acoustic performance of light steel framed systems

Requirements of Part E of the Building Regulations

Approved Document E (2003 Edition) sets out minimum Until 2003, the Standardised Weighted Level Difference
standards of acoustic performance for walls and floors DnT,w was used as the single figure index for airborne
between dwellings (separating walls and floors) that sound insulation in the Building Regulations. The 2003
satisfy the requirements of Part E of the Building Approved Document E introduced a new measurement
Regulations. The 2003 amendments impose more index, DnT,w + Ctr to replace the existing DnT,w for airborne
demanding standards for the control of noise in sound. The Ctr term is a spectrum adaptation term,
buildings. These mainly concern residential buildings, which adjusts the index taking additional account of the
both dwellings and other building which contain ‘rooms noise spectrum in residential buildings. The Ctr term is
for residential purposes’ such as hotels, hostels and generally negative and reflects particularly the
buildings where people may sleep. School buildings are performance at the low frequency end of the spectrum.
also affected by the new requirements. Thus, a DnT,w + Ctr rating is generally lower than the
DnT,w rating for the same construction. Due to the
Approved Document E, which also provides guidance on difference in performance over the spectrum, the
how the requirements can be met, came into effect in DnT,w + Ctr index is likely to be more demanding for
July 2003. The requirements for site testing of dwellings lightweight constructions.
have been delayed until January 2004.
Impact sound transmission is measured by L’nT,w, the
The requirements cover: Standardised Weighted Impact Sound Pressure Level.
• Acoustic insulation of separating walls and floors
between newly built dwellings, and dwellings formed Site testing
by a material change of use. Approved Document E (2003 Edition) introduced a
• Acoustic insulation between hotel rooms, boarding requirement for pre-completion site testing of acoustic
house rooms, and other rooms used for residential performance. At least 1 in 10 of every type of
purposes such as student halls of residence and key separating wall and floor at all residential construction
worker accommodation, formed by new-build or by a sites are to be tested to show that the minimum
material change of use. performance standards in Table 1 have been met. The
requirement for testing applies to residential buildings of
• Acoustic insulation between rooms within a dwelling all kinds, both purpose built and formed by a material
formed by new-build or by a material change of use. change of use. However, for new-build houses and flats
• Acoustic characteristics of common parts of only, there may be an alternative option to use Robust
apartment buildings. Standard Details.
• Acoustic characteristics of schools.
Robust Standard Details
Robust Standard Details (RSDs) are being developed as
Single figure ratings an alternative way of showing compliance for new
The performance standards include airborne sound houses and flats only, which avoids site testing. They
insulation of walls between dwellings (separating walls), comprise standard details that have undergone a
and both airborne sound insulation and impact sound thorough development and testing procedure and have
transmission for floors between dwellings (separating been shown to have acoustic performance considerably
floors). These are set out in Table 1. The performance in excess of the minimum standards of the Building
standard for walls and floors within dwellings should Regulations. A range of light steel frame Robust
have a minimum laboratory value (not site tested) for Standard Details are currently under development. An
airborne sound insulation (Rw) of at least 40 dB. announcement about the possibility of using RSDs
instead of site testing is expected in late 2003.

Table 1 Minimum performance standards of Approved Document E (2003) for site measurement
Separating walls Separating floors
Building type
DnT,w+Ctr DnT,w+Ctr L’nT,w
Purpose built dwellings ≥ 4 5 dB ≥ 45 dB ≤ 62 dB
Dwellings formed by material change of use ≥ 43 dB ≥ 43 dB ≤ 64 dB
Purpose built rooms for residential purposes ≥ 43 dB ≥ 45 dB ≤ 62 dB
Rooms for residential purposes formed by material change of use ≥ 43 dB ≥ 43 dB ≤ 64 dB

4
Walls - typical constructions and performance
Suitable for an internal wall within a dwelling
• One layer of gypsum board ( ≥ 10 kg/m2 )
• Light steel studs
• 25 mm (min) unfaced mineral wool quilt or slab (10 to 60 kg/m3)
• One layer of gypsum board ( ≥ 10 kg/m2 )
• Rw = 42 to 45 dB Fire rating = 30 minutes

• 2 layers of gypsum board

• Light steel studs
• 25 mm (min) unfaced mineral wool quilt or slab (10 to 60 kg/m3)
• 2 layers of gypsum board
Rw = 48 to 53 dB Fire rating = 60 minutes
May be suitable for a separating wall
(depending on flanking conditions)
• 2 layers of gypsum board ( ≥ 2 3 kg/m2 )
• Proprietary resilient bars
• Light steel studs (min 100 mm)
• 50 mm (min) unfaced mineral wool quilt or slab (10 to 60 kg/m3)
• Proprietary resilient bars
• 2 layers of gypsum board ( ≥ 2 3 kg/m 2 )

DnT,w + Ctr = 50 dB Fire rating = 60 minutes

May be suitable for a separating wall

(depending on flanking conditions)
• 2 layers of gypsum board ( ≥ 23 kg/m2 )
• Staggered stud light steel frame system with every second stud
connected to the lining on one side
• 50 mm (min) unfaced mineral wool quilt or slab (10 to 60 kg/m3)
around the studs
• 2 layers of gypsum board ( ≥ 23 kg/m2 )

DnT,w + Ctr = 48 to 50 dB Fire rating = 60 minutes

Suitable for a separating wall

• 2 layers of gypsum board ( ≥23 kg/m2 )
• Light steel studs
• 50 mm (min) unfaced mineral wool slab (30 to 60 kg/m3) between the
studs (with minimal structural fixings between studs)
• Light steel studs
• 2 layers of gypsum board ( ≥23 kg/m2 )

DnT,w + Ctr = 52 to 56 dB Fire rating = 60 minutes

Suitable for a separating wall

• 2 layers of gypsum board ( ≥23 kg/m2 )
• Light steel studs with 50 mm (min) unfaced mineral wool quilt or slab
(10 to 60 kg/m3)
• Optional inner sheathing of 10 mm plasterboard or OSB
• 25 mm (min) space between the leaves
• Optional inner sheathing of 10 mm plasterboard or OSB
• Light steel studs with 50 mm (min) unfaced mineral wool quilt or slab
(10 to 60 kg/m3)
• 2 layers of gypsum board ( ≥23 kg/m2)
DnT,w + Ctr = 52 to 58 dB Fire rating = 60 minutes

5
Acoustic performance of light steel framed systems

Separating walls

Separating walls must meet the requirement for airborne • No back to back service penetrations.
sound insulation only. The most common separating • Electrical sockets and switch boxes should be
walls using light steel framing have two skins staggered and backed with two layers of plasterboard
structurally and physically independent of each other in of density 23 kg/m2 (see page 11).
order to provide the necessary acoustic separation. In
effect, two walls are constructed along side one another • Where the separating wall meets a floor (including
and structural or rigid links between them that could ground floor) the floor structure should not be
transmit acoustic vibrations are avoided. continuous across the separating wall.

The essential requirements for good acoustic insulation Resilient bars used to attach the plasterboard to the light
of separating or party walls in lightweight dry steel framing can reduce the direct transfer of sound into
construction are: the structure further, and lead to enhancement of
• A double leaf separating wall construction with a gap acoustic insulation.
between the frames of at least 25 mm.
Increasing the mass of each plasterboard layer by
• An independent structure for each leaf with minimal increasing density or thickness will further improve
connections between. acoustic insulation.
• A minimum weight of 23 kg/m2 in each leaf (e.g. two
layers of 15 mm firecheck or soundcheck In some applications, single stud separating walls with
plasterboard, with staggered joint to avoid air paths). two layers of 15 mm soundcheck plasterboard fixed to
• A minimum of 200 mm separation between the two both sides using resilient bars, or staggered stud walls
plasterboard inner surfaces. can be used (see page 5) However, care needs to be
taken at all junctions, as flanking transmission is more
• Good sealing of all joints and junctions to avoid air
difficult to avoid. This construction is used more often in
paths.
non load-bearing applications.
• A minimum 50 mm thick unfaced mineral fibre quilt
(10 to 60 kg/m3) within both of the leaves or See also the Section on flanking details.
between the leaves.

2 layers of gypsum board

to give a minimum density of 23 kg/m²

Light steel studs

Minimum 50 mm
of mineral wool
(10 - 60 kg/m³)

Clear cavity
between studs

Light steel studs

2 layers of gypsum board

to give a minimum of 23 kg/m²

Figure 4 Typical double leaf separating wall construction

6
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Floors - typical constructions and performance

Suitable for internal floors within a dwelling

• 18 – 22 mm chipboard (or similar) to give 15 kg/m2
• Light steel joists
• 100 mm of unfaced mineral wool quilt (10 to 30 kg/m3)
between the joists
• 12 mm gypsum board (≥10 kg/m2)

Rw = 42 dB
Fire rating = 30 minutes

Suitable for use as a separating floor

• 18 mm chipboard or similar
• 19 mm gypsum board
• 25 mm to 30 mm of resilient layer (mineral wool 120 to
200 kg/m3)
• Chipboard or OSB base
• Light steel joists (min 150 mm deep)
• 100 mm of unfaced mineral wool quilt (10 to 30 kg/m3)
between the joists
• Proprietary resilient bars
• 2 layers of gypsum board (≥23 kg/m2)

DnT,w + Ctr = 48 to 52 dB L’nT,W = 54 to 57 dB

Fire rating = 60 minutes

Suitable for use as a separating floor

• 18 mm chipboard or similar
• 19 mm gypsum board
• Proprietary timber batten bonded to foam strip (with insulation
between – not beneath batten)
• Chipboard or OSB base
• Light steel joists (min 150 mm deep)
• 100 mm of unfaced mineral wool quilt (10 to 30 kg/m3)
between the joists
• Proprietary resilient bars
• 2 layers of gypsum board (≥23 kg/m2 )

DnT,w + Ctr = 50 to 52 dB L’nT,W = 54 to 57 dB

Fire rating = 60 minutes

Suitable for use as a separating floor

• 18 mm chipboard or similar
• 19 mm gypsum board
• Light steel floor joists
• 100 mm of unfaced mineral wool quilt (10 to 30 kg/m3)
between the joists
• 10 mm OSB or similar
• Air space between floor and ceiling joists
• Light steel ceiling joists
• 2 layers of gypsum board (≥23 kg/m2 )

DnT,w + Ctr = 46 to 54 dB L’nT,W = 56 to 60 dB

Fire rating = 60 minutes

7
Acoustic performance of light steel framed systems

Separating floors

For separating floor constructions between dwellings, They are covered by a sheet of plasterboard and the
both airborne and impact sound transmission must be final floor finish board (usually chipboard). Care should
addressed. High levels of acoustic insulation are be taken that screws do not penetrate through the
achieved in lightweight floors by using a similar resilient layer.
approach as outlined for walls. This involves separating
the floor and ceiling finish layers from the underlying Alternatively, it may be possible to use a lightweight
structure as far as possible with resilient layers that screed on a resilient layer such as mineral wool or a thin
reduce the transfer of sound vibration. proprietary foam.
The ceiling usually consists of two layers of plasterboard
The resilient layer beneath the floor finish contributes to with a minimum overall mass of 23 kg/m2 (such as 2
insulation against both airborne and impact sound. The layers of 15 mm sound-check plasterboard), fixed to
resilient bars fixed to the underside of the steel joists resilient bars that are fixed to the underside of the steel
partially isolate the dry lining layer from the structure. A floor joists. The resilient bars reduce the rigidity of the
mineral wool quilt in the cavity between the steel joists connection between the plasterboard and the structure
provides sound absorption. above, reducing the acoustic vibration that is
transmitted.
A typical floor will consist of light steel joists (generally
over 150 mm deep), with a mineral wool quilt (10 to Impact sound transmission in lightweight floors is
30 kg/m3) between to act as an absorption layer. A reduced by:
structural floor deck is laid on the joists comprising either
• Specifying an appropriate resilient layer with correct
a timber based board (chipboard, OSB or plywood) or a dynamic stiffness under imposed loadings.
profiled steel deck.
• Ensuring that the resilient layer has adequate
On the structural deck, an acoustic platform or raft floor durability.
is usually installed: • Isolating the floating floor surface from the
A platform floor consists of a dense mineral wool (120 surrounding structure at the floor edges. This can be
to 200 kg/m3) resilient layer, usually 30 to 50 mm thick, achieved by returning the resilient layer up the edges
covered by a sheet of plasterboard (to provide additional of the walking surface (see Section on flanking
mass) and the final floor finish board (usually chipboard). transmission).
A raft floor consist of proprietary timber battens which Further improvements in the design of lightweight floors
have a resilient foam bonded to them, and may have a can be achieved by separation of the floor structure from
thin (20 mm) mineral wool quilt between. the ceiling structure, using separate floor and ceiling
joists.

18 mm T&G chipboard

Gypsum board (13 kg/m²)

Mineral wool between

battens (not beneath)

Chipboard
or plywood
base layer

100mm mineral wool

(10 - 30 kg/m³)
betweeen the joists

Proprietary acoustic Plasterboard mounted on

battens on resilient pads proprietary resilient bars

Light steel joists at 600c/s 2 layers of gypsum board

min. 150 mm deep (min. 23 kg/m³)

Figure 5 Typical separating floor using a built up platform floor

8
 Flanking transmission

Flanking transmission occurs when airborne sound • Direct contact between the wall lining and floor finish
travels around the separating element of structure board should be avoided, to reduce vibration transfer.
through adjacent building elements such as external Wall plasterboard linings should be stopped about
walls. Flanking transmission is difficult to predict 5 mm above the floor decking. The gap should be
because it depends on the details of the floor and wall filled with acoustic sealant (Figure 7).
junction and the quality of construction on site. It is
• Internal non-load bearing walls within an apartment
possible for a building to have separating walls and floors
should, if possible, not break through the ceiling of a
built to a high specification but for considerable sound to
separating floor, and should not touch the steel floor
be transmitted through flanking elements that are
joists.
continuous across the separating elements.
• Where insulation is placed in the thickness of the steel
To avoid flanking transmission the following measures studs in a separating wall, additional mineral wool
are suggested: insulation should be placed in the cavity between the
frames at intersections with external walls and
• The light steel frame structure of an external wall
separating floors (Figure 8).
should not be continuous across junctions with a
separating wall. A physical break should be • Avoid any air paths through separating elements. Seal
maintained, and any sheathing board should also be at junctions and at service openings.
discontinuous at this point (Figure 6).
• The joints in successive layers of lining board should
• Where a separating floor meets an external or party be staggered.
wall, the void within the wall between the studs • Any gaps should be sealed with acoustic sealant.
should be filled with mineral wool to at least 300 mm
above and below the separating floor (Figure 7).

Flexible cavity fire stop Maintain a break in rigid insulation

sheathing board and steel framing

Rigid insulation
sheathing board
Optional additional insulation
in external wall Two layers of gypsum board
on separating wall

Mineral wool in separating wall

Figure 6 Typical junction of separating wall and external wall

9
Acoustic performance of light steel framed systems

Flanking details

Rigid insulation sheathing board

Break in rigid insulated sheathing board

Cavity in
filled with flexible fire stop
external wall
with cavity tray over

Acoustic Acoustic raft or

sealant platform floor

min. 150 mm
Brick (or other)
external cladding

Mineral Light steel

wool floor joists
Two layers of gypsum board
(min. density 23 kg/m²)
Fill void between studs
with mineral wool
300 mm above and below floor

Figure 7 Typical separating floor to external wall detail

2 layers of gypsum board

(min. 25 kg/m²)

Small gap filled with

acoustic sealant
Platform floor
Proprietary raft floor

Light steel floor joist

(min. 150 mm) Two layers of gypsum board
Resilient bars (min. density 23 kg/m²)

Additional mineral wool

Min. 50 mm of mineral wool
in floor zone
between frames

Figure 8 Typical separating wall to separating floor detail

10
 Service penetrations Site acoustic tests

The Building Regulations allow wall and ceiling linings to Following the 2003 revisions of Part E of the Building
be penetrated so that services can pass through provided Regulations, pre-completion site testing is required for all
that fire and acoustic integrity is maintained. Since constructions unless Robust Standard Details are
acoustic performance can be particularly affected by air accepted, and used, in newly built houses and
paths through the construction, special care is required apartments. These tests must be carried out when the
around service penetrations. building is largely complete, with doors, skirting boards,
electrical sockets and switches in place, but unfurnished
The following aspects should be considered: and without a carpet (except with certain concrete and
composite floors). Cupboards and kitchen units should
• The location of electrical sockets and switches should have their doors open and be unfilled. The site must be
be carefully considered and back to back installations reasonably quiet during the tests.
should be avoided, in separating walls.
• Where electrical sockets in separating walls cannot be Site measurements should be carried out in accordance
avoided they should be backed by two layers of with BS EN ISO 140-4-1998 for airborne sound and
plasterboard and mineral wool (see Figure 9). BS EN ISO 140-7-1998 for impact sound.
• Seals, acoustic quilts, and cavity barriers should be
used where appropriate to seal air gaps. For airborne sound measurements, a steady sound of a
particular frequency is generated in the source room and
• Down-lighters in separating floors should be avoided the sound pressure level in the source and receiving
as they create a significant penetration through the rooms are compared to ascertain the reduction.
plasterboard lining causing acoustic, fire and
air-ightness problems. For impact sound measurements a standard impact
• Where down-lighters cannot be avoided they should sound source (tapping machine) is used to strike the floor
be backed by 2 layers of gypsum board (>23 kg/m2). and the impact sound pressure level is measured in the
room below.
• Services in the floor can be accommodated in a raft
floor, between the acoustic floor battens. For both airborne and impact measurements, the
• Services within the resilient material of a platform receiving room levels must be corrected to 0.5 s
floor should be avoided. reverberation time before comparison with the
performance standard. Measurements are taken at 16
one third-octave frequency bands across the hearing
spectrum from 100 Hz to 3150 Hz.
Electrical
socket box
To convert the site measurements into a single figure
rating, the method set out in EN ISO 717 (Parts 1 and 2)
compares the set of 16 measured results with a
reference curve. The rating is made by considering only
those measured values which fall short of the reference
curve and choosing a reference curve where the sum of
the negative deviations (over the 16 measured third-
octave bands) is as large as possible but not greater than
32 dB. The value of the reference curve at 500 Hz gives
the single figure rating. For rating measurements of
airborne insulation Ctr must also be calculated from the
measured figures.

Figure 9 Integration of electrical socket and switch

boxes in separating walls

11
Acoustic performance of light steel framed systems

Light steel framing checklist

Acoustic performance Sustainability

• A variety of proven, efficient, lightweight separating • Low waste in construction.

wall and floor constructions can be built. • Less materials used.
• Good acoustic insulation is achieved through the use • Steel is highly recycled and recyclable at end of life.
of several layers of mass provided by board materials • Adaptability for changing future requirements.
such as plasterboard and chipboard with minimal rigid • Benefits of off-site manufacture.
connections between them.
• Decoupling of the structure is achieved using double Energy efficiency
leaf construction, resilient bars and resilient layers.
• Double leaf separating walls with mineral wool quilt • High levels of insulation easily included.
between and two layers of plasterboard either side • Low U-values easily achieved.
have an established record of good acoustic • Thermal bridging avoided.
performance.
• Potential for air-tight construction.
• Separating floors require plasterboard ceilings to be • Robust standard details developed.
fixed on resilient bars to increase decoupling.
• Lower operating costs for the owner.
• Acoustic raft or platform floors should be used on the
separating floors to deal with impact sound Rethinking Construction
transmission.
• Details have been developed for junctions between • Greater speed of construction.
separating walls and floors and external walls to avoid • Increased value to client.
flanking transmission. • Increased productivity.
• Good site practice is important to ensure that details • Less ‘call backs’ for making good.
are correctly constructed.
• Increased rate of return for the builder.
• Predictability of process.
• Increased quality.

Sources of information Relevant publications

The Steel Construction Institute Building design using cold formed steel sections: Light steel
Tel: 01344 623345 framing in residential construction (P301), SCI, 2001
www.steel-sci.org
Building design using cold formed steel sections: Acoustic
Corus Construction Centre insulation (P128), SCI, 1993
Construction Advisory Service
Limiting thermal bridging and air leakage: Robust construction
Tel: 01724 405060
www.corusconstruction.com details for dwellings and similar buildings
DTLR/DEFRA, TSO, 2001
Corus Colors
Energy efficient housing using light steel framing (P307)
Cladding Advisory Service
Tel: 01244 892434 SCI, 2002
www.colorcoat-online.com Case studies on light steel framing (P176), SCI, 1997
U-values for light steel frame construction (BRE Digest 465)
Building Research Establishment 2002

This project was supported by Corus Colors

Web sites:
For information on light steel: www.steel-sci.org/lightsteel

For 24x7 information on steel construction : www.steelbiz.org The Steel Construction Institute
Silwood Park, Ascot,
For information on Robust Standard Details: www.rsd.napier.ac.uk Berks, SL5 7QN
Tel: 01344 623345 Fax: 01344 622944

SCI P320 Acoustic performance of light steel framing ISBN 1 85942 143 1 © 2003 The Steel Construction Institute

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