Acoustic Ratings


This newsletter is about :

  1. acoustic ratings or soundproofing
  2. acoustic rating to floors, including timber floating floors
  3. windows

The following information maybe of interest to you when undertaking future refurbishments. This information is not a highly technical specification but gives an overview. Our office can be contacted if a more detailed report is required, particularly from other specialist acoustic engineers.

We have inspected many buildings where timber floating floors have been installed, but it appears that little consideration is given to the additional noise that can affect the building, including within unit buildings. For this reason we provide the following information which maybe of assistance with future refurbishment of buildings, particularly units.

Acoustic Rating or additional soundproofing which can be added to a building

The following pages provide information on

  • additional soundproofing to plasterboard walls
  • additional soundproofing to timber floating floors
  • additional performance and soundproofing windows

When the Building Code of Australia was introduced several years ago one of the main changes was the downgrading of the acoustic rating between units. There has been some controversy in Sydney over the years, particularly with unit holders who can hear audible noises from adjoining units. The reason why this is occurring is that within most new buildings the method of construction has changed. Where previously the walls between units and internal walls were constructed of bricks, this is now a lightweight construction. The building mainly consists of a concrete shell which allows lightweight non-structural internal partitions. The walls between individual units again is a lightweight construction, however various systems can be completed to meet the acoustical rating as specified by Council. It is difficult after completion of the building to improve the acoustical rating between individual units, as well as internal rooms. Standard plasterboard, or gyprock, linings as well as fibreglass and polyester insulation have a poor acoustic rating, but are the materials used in new construction. The plasterboard manufacturers have now brought out a new material which appears to have a substantially improved acoustical rating and should be considered as a replacement if the existing linings are not to the owners satisfaction.

For further information on soundproofing we suggest you download a brochure from: here

Improvements to acoustic rating to floors, including timber floating floors

We have inspected many properties where a timber floating floor has been installed. In the majority of cases it does appear that there has been no consideration to the noise reduction to the areas below which can include unit construction, as well as noise from the first floor area within a residence. Carpet acts as a noise insulator and the underlay to the carpet also assists in the reduction of sound and impact reduction. Where a timber floating floor exists, the audible noise such as that from a television or stereo can transmit through the timber floor. Additionally, impact noise such as a person walking on the floor is far more audible. Our discussions with various suppliers and installers of timber floating floors indicate that the cost for the project is paramount and therefore unless a demand is made for noise reduction then it is not included within the majority of the floating floors which are fitted.

We have undertaken enquires with various manufacturers of products which can be readily installed to substantially reduce noise impact through a floor. This can include the first floor area of a residence, as well as within unit/townhouse construction. The following particularly applies to timber floating floors, but can also be included where additional soundproofing is required below carpets. Where the government has been involved in providing additional soundproofing to houses around the airport, many products were tested. The soundproofing used within the roof void of these buildings does not consist of the usual fibreglass, polyester, rockwool or pumped pulp material. A much higher acoustical rating can be achieved by a rubberised membrane which is fitted over the top of the ceiling joists. This technical knowledge now appears to be transferred into many materials, several of which have only recently become available in the marketplace. These materials appear to incorporate a similar soundproofing layer which is fixed to a softer material which provides a cushioning affect below the floor finishes. This is particularly relevant where timber floating floors are installed where not only a softer feel is provided when walked upon, but also an acoustical layer is fitted. There are several manufacturers of this type of material. Should additional information be required, then our office can be contacted for more information. Again, where a major problem exists, then an Acoustical Engineer should be consulted.

For further information and brochures we suggest you download the following : and



Windows have made substantial improvements in recent years and mainly come under the two following headings.

  • Performance in respect of waterproofing
  • Improvements in glass, including reduction of heat loss, additional security and safety as well as noise reduction
Performance in respect of waterproofing

Windows are now required to be provided with a performance sticker at the time of delivery. This has been phased in over the last couple of years. The majority of windows, both aluminium and timber were designed some time ago for a typical exhibition house at Baulkham Hills. Whilst this is adequate for most applications, the same windows are placed in buildings in an exposed location such as near the sea, on a hilltop and other locations where the windows can be affected by wind driven rain. For this reason there have been problems with several buildings with water entry, as well as deflection of windows with large panels such as patio sliding doors. The Australian Window Association has been at the forefront for improvements of these windows. Windows now come in various gradings and windows can be installed on buildings in exposed locations and not be affected by water entry. This includes buildings at the northern end of the beach, hilltops and other wind swept areas where the wind is able to collect rain and push it against the building in a horizontal direction. It is our experience that very few of the window replacement companies are providing adequate information and we have been seen some recent replacements with inadequate graded windows. Should further information be required then our office maybe able to assist.

Glass Improvements

The current Building Code of Australia and the Glazing Code requires safety glass be fitted in areas where there is an elevated risk of injuries such as glass on patio handrails, shower screens, doors including patio sliding doors, and sidelight panels to windows. In essence, the majority of the remainder of the glass is a 3mm float glass which does allow substantial loss of heat within a building and provide minimum protection against noise and no security.

Currently SMART GLASS® should be an option that should be considered with any window replacement. In essence, the majority of this glass is a 6mm laminated glass but different characteristics can be incorporated to suit the individual application. The energy ratings of buildings will come in force in the near future and the type of glass which is used will be important to achieve an acceptable rating. Several types of glass can be fitted which will substantially reduce the heat loss within the building during winter and reduce the heat ingress during summer. This usually incorporates a film being applied to the glass to reduce thermal transfer of heat. In other applications, it maybe desired to reduce noise in the building from a nearby road, railway, airplane as well as noise from a large number of persons gathering or passing by. In other situations it maybe desired that additional security be provided to the building. In this case as the plastic sheeting between the two layers of glass is provided with a special film which does not allow the glass to disintegrate when it is hit, even with a sledgehammer. This overcomes the need for security grilles to a building but still provides substantially improved safety. More information can be obtained from the glass manufacturers by downloading from  Or ring the Smart Glass Hotline on
1800 810 403.

David Hall Building Appraisals
November 2003

Newsletter January 2003



Unit building are often provided with a magnesite coating to the top surface of the internal floor. This type of coating was regularly used in unit construction during the 1960’s and 1970’s, but also in some buildings prior to and later to this time. The magnesite coating was installed mainly as a levelling compound to provide an adequate level surface to the floor. Additionally, this is a cork type material which is soft and provides a softer finish to the floor and was superseded by the more recent improved carpet underlays. Problems are now emerging with this magnesite that when it becomes damp, or wet, it sets up a chemical reaction with the steel reinforcing to the main part of the concrete structure, or floor. This chemical reaction sets up accelerated rust which attacks the structural core of the floor slab and building. In extreme cases, the floor in the affected areas can noticeably lift. The problems occurs when water entry transpires, particularly around leaking windows or patio door units. Additionally, a chemical reaction can be set off particularly if the internal carpets are steam cleaned on a regular basis. The extent of any future repairs, or replacement, would depend upon further exploratory works to the majority of the building and can involve major rectification costs. Some strata managers are recommending that the magnesite be removed when the unit is refurbished.

 2003 03 floor 01


Due to recent exposure of the abuse or compromising of certification of unit buildings works we are able to provide a specialist consultant to certify unit and commercial buildings. By law these buildings must b checked and certified every year to warrant the sprinklers, smoke alarms etc are correctly working. There are known cases of developers pressurising contractors to certify their work which does not meed the requirements of the Building Code of Australia.

Our report is not a Schedule 15A Certificate on the building as this requires specialist contractors with additional expertise. A 15A Certificate is an annual requirement to have the building certified to ascertain if it meets the requirements of the Building Code of Australia, mainly in respect of fire provisions, but also hydraulics.

This is a requirement for annual testing and certification that the building has adequate and functioning equipment and covers automatic fire detection and alarm system, sprinkler system, emergency lighting, exit signs, fire dampers, fire doors, fire hydrants, hose reels, mechanical ventilation system including possible stairwell pressurization as well as other systems which maybe incorporated within the building.

New changes have come into force relating to energy efficiency for new houses approved from 1 January 2003. An overview is as follows:


BUILDING CODE OF AUSTRALIA which is the standard to which buildings are constructed, now includes a mandatory requirement for a greater energy efficiency within all Class 1, or standard residential houses. This is a mandatory requirement for new houses approved after 1 January, 2003. A brief overview to the new requirements is listed below.

On 30 August 2002, the Australian Building Codes Board announced that national energy efficiency measures for houses will be introduced in the Building Code of Australia on 1 January 2003.

The adoption of these new national requirements forms an important part of the Commonwealth Government’s strategy to address global warming. Energy efficiency measures for commercial buildings will follow.


Under the Kyoto Protocol, Australia’s target is to limit greenhouse gas emissions to only 8% above 1990 levels. Increased energy efficiency is one of the most important ways to achieve this target.

After taking into account the views of industry, the Commonwealth Government announced in July 2000, that agreement had been reached with State and Territory Governments to introduce mandatory energy efficiency standards into the Building Code of Australia, as part of the strategy to reduce greenhouse gas emissions from buildings.

The development of the Building Code of Australia energy efficiency measures for houses was undertaken by the Australian Building Codes Board in conjunction with the Australian Greenhouse Office and other key stakeholders.

Scope of the Building Code of Australia Energy Efficiency Measures:

In Summary, the Building Code of Australia housing energy cover five main areas:

Building Fabric - to control conduction of energy through the building fabric. Provisions primarily relate to reflective materials and insulation levels in the roof, walls and floor depending on the climate.

  • Solar radiation: to control discomfort in warmer climates from solar radiation and to provide solar heating in cooler climates.

Provisions require external glazing to be limited in size according to likelihood of heat loss from the building interior and to be protected from unwanted solar heat.

  • Building Sealing: to control air leakage into or out of a building, and hence avoid an increased need for heating and cooling.

Provision will increase a building’s air tightness through closable openings, such as chimneys, flues and exhaust fans, and sealing around elements such as windows, doors, roof lights and penetrations.

  • Air Movement: to ensure adequate external and internal openings are provided to permit a building to be ventilated naturally or with fan assistance.

Provisions will affect buildings in hot and temperate climates where increased ventilation can provide useful cooling instead of using energy for air conditioning.

  • Services: to avoid wasting of energy in building services systems.

Provisions primarily cover insulation of water piping to central heating systems and storage hot water units, and insulation of ductwork associated with heating and air conditions systems.

The proposed energy measures vary from location to location and are based on a climate zone map comprising eight zones. This map has evolved from one developed some time ago by the Bureau of Meteorology.

Should you have any further queries in respect of the new energy efficiency requirements, then please our office as we are happy to provide a copy of the new requirements to date.

The following are case studies which maybe of interest now or in the future.





2003 03 brick 01

An inspection of this building recently revealed one of the common causes for cracks to brickwork. This is the lack of tying in of brickwork. The photograph shows where the wall has been constructed and not tied into the adjoining brickwork. In this case a half brick has been cut and abuts the joining wall. There is no form of tying in of the brickwork, nor fixing. This brickwork supports a door jamb and is likely to result in cracking of the vertical join in the brickwork mainly when doors slam, or similar. This problem could have been overcome by construction of the two brick walls at the same time with the brickwork being interlocking.


2003 03 brick 02


The brickwork to this lintel is supported by a steel angle, however defects within the brickwork are likely to cause future cracking. The brickwork is supporting a concrete slab above which has a reasonable overhanging cantilevered balcony which would impose additional loads on the brickwork. Cracks are likely to occur for the following reasons:

1. A rebate, or square section, was left out of the brickwork at both ends to allow for the installation of steel beam. All the brickwork above this beam was not tied-in, or bonded, to the brickwork at the end.
2. The brickwork above the lintel has been placed on their edge and not on their flat. For this reason the bearing width of brickwork is reduced from the normal 110mm to 75mm.
3. The brickwork has been incorrectly placed on a mortar bed. This practice often results in cracking, or crumbling, of the mortar as the mortar does not bond to the steel lintel.
4. A thick strip of compressed fibro sheeting has been fitted to the brickwork to provide some stability while laying the bricks, but does compromise the structural adequacy of the brickwork.
5. A split half brick is placed above and below this fibro strip. The width of the bearing of the brickwork is reduced to 75mm, however the bricks are not engineered, or designed, to support structural loads on their edge. The centre core holes further reduce the structural capacity of the bricks. The brickwork, particularly the half bricks, are vulnerable to crushing due to the weight of the concrete above.



2003 03 brick 03

A recent inspection of a building showed the flashings to the base of the cavity have been installed. These flashings are designed to collect any water entry to the building and discharge it to the outside. On this particular house, the outside brickwork is to be rendered. In the majority of cases renderers will cover the weep holes which are there to allow the water to escape out of the base of the cavity. Should this occur, then water cannot flow out of the weep holes and will continue to flow around the base of the cavities until it finds the easiest point of exit. In this case the end of the flashing has not been turned up at the ends and would allow any water trapped within the cavity to form a water leak at the sliding door which is yet to be fitted. The flashing in this case should have been turned up at the ends to prevent the leaks at the door sill.

2003 03 brick 04

This is a sill flashing which has been fitted for a sliding door unit. It is expected leaks would occur as the flashing is not of sufficient length to allow for the ends to be turned up. Additionally, it can be seen holes and damage is evident to the flashing. This is a condition of the flashing immediately prior to the installation of the door unit. The repairs in this area would involve complete removal of the inadequate flashing and replacement.


SPALLING OF CONCRETE (concrete cancer)

2003 03 spalling 01

Spalling of concrete is commonly called concrete cancer. This occurs when the steel reinforcing rods within the concrete are affected by moisture, or a salt environment, which causes the steel to rust which then expands and pushes off the surface the concrete that encases the steel reinforcing.

This problem mainly exists in units built during the 1960’s, 1970’s and early 1980’s and mainly closer to a salt environment. This does not preclude that spalling problems occur in other environments, such as concrete slabs over garages where the area above is landscaped, or provided with turf which is substantially affected by water and creates a damp environment to the concrete slab. The problem occurs because the steel reinforcing has insufficient “cover” which allows either moisture or salt laden air to affect the steel reinforcing. Most of these earlier practices were overcome with the Concrete Codes which were introduced during mid 1980’s and change in practices within the steel reinforcing industry. Problems of a lesser nature in new buildings may occur, but this mainly where rust spotting is evident where the support “chairs” are affected by the salt or moisture.

Spalling repairs can be successfully undertaken providing it is properly treated. There are many reputable companies that complete this type of work on a regular basis. This can also involve the chemical analysis of the concrete to ensure that the materials and practices which are undertaken do not cause future failure. Should the works not be correctly undertaken, as is illustrated below, then ongoing substantial repairs can be expected. Where the Owner’s Corporation accepts the cheapest quote and does not seek referrals, then problems may occur.

An example of sub-standard workmanship is shown as follows:

On this block of units the lower balcony is currently undergoing substantial remedial works.

2003 03 steelflooring 01

2003 03 steelflooring 02

The original steel reinforcing rods have been cut, or removed at the edge of the repairs. The original cross reinforcing rods have been removed. A new mesh has been fitted, but is not tied in any form to original steel reinforcing and is therefore not structural

2003 03 steelflooring 03

2003 03 steelflooring 04

In some cases new steel reinforcing rods have been fitted to every second original steel reinforcing rod but have been welded with a 30mm lap to the original reo.

The new mesh which has been fitted is not of a structural size to provide structural support to the bottom of the slab.

2003 03 steelflooring 05

2003 03 steelflooring 06

The new mesh which has been fitted is also bolted and fixed to the affected concrete slab above to provide adequate fixing.

2003 03 steelflooring 07

2003 03 steelflooring 08

This confirms the mesh is only fitted to provide some bonding agent for the later rendering to the underside of the slab.

The repairs in this area will fail as the mesh is not galvanised, or coated, with an epoxy and will be affected by future rust. As is evident, but part of the other works which have been completed, a porous render to a thickness of approximately 25mm will be applied over the steel reinforcing.

2003 03 steelflooring 09

2003 03 steelflooring 10

In this application the steel requires a minimum of 50mm cover of compacted concrete so that the salt environment does not cause future rust. Additionally, the repairs do not in any form take into consideration deficiency in the balcony slab and the reduction in structural slab.



An additional future structural concern with unit buildings is in respect of structural settlement and deflections of cantilevered concrete balconies. This mainly occurs where the balcony is provided with a perimeter brick railing which provides substantial loads at the outer edge of the slab. The weight of the brickwork causes the balcony slab to defect and results in reasonable gaps between the brick railing and original wall of the building. Over time this deflection will continue and eventually causes a settlement crack at the top of the concrete balcony near the building. Where this is of a concern is with unit buildings located near the sea. The salt environment and rainwater causes the steel within the concrete slab to rust at the point where the crack is occurring. Whilst we have not seen too many failures of concrete balconies it is expected that this will become more common place in the future and require major remedial works.

January 2003 ©