Westbrook, a comprehensively planned Estate
Westbrook has been meticulously planned by the developer in association with Wyndham City
Council and the Victorian State Government. Living at Westbrook has the advantage of Tarneit rail
station being on site, with many lots within walking distance. As part of the planning process for the
new rail line, the State Government has imposed mandatory standards that require houses built
near the rail line be designed so that their internal bedroom noise levels meet an approved acoustic
standard.
These acoustic standards are new requirements that do not generally exist elsewhere in Victoria.
However, the State Government (through its new passenger rail noise policy) is gradually applying
the same acoustic requirements to other greenfield housing estates located near rail lines around
Melbourne. Over time these new requirements will become more common.
This document provides a general overview of the requirements and how they are expected to
impact on your build. You cannot rely on this document in order to meet the requirements. You will
need to obtain advice from an acoustic consultant through your builder so that you understand
exactly what compliance with the requirements means for you and your block, including any
additional building cost implications.
The impact of the requirement on your block and dwelling
The impact of the new standards can vary from little or no requirement to more extensive
requirements depending on when your house is constructed, the location of the dwelling and the
house design proposed. Because the impact of the requirement will normally vary depending on a
number of variables, you will need to obtain advice from an acoustic consultant through your builder
so that you understand exactly what compliance with the requirements means for you and your
block, including any additional building cost implications.
Westbrook has employed two of Melbourne’s leading acoustic consultants (Renzo Tonin &
Associates and Marshall Day Acoustics) to measure the noise levels from the trains and to confirm
the correct approach that builders will need to adopt to meet the requirement. Our team will be
able to discuss any technical requirements directly with your builder or their acoustic consultant, if
required.
Our consultants have established that for most dwellings, generally, if they are single storey brick
veneer (which the vast majority of houses built in the area are) and not immediately abutting the rail
line and they are constructed after the houses abutting the rail line are completed then they are
unlikely to require any upgrades or special treatment to meet the requirement. In this case there
would be no extra cost to build your home. This would be the case because the houses up against
the rail line act to shield the houses behind them from the rail noise. If that is the case, your builder
will be able to confirm with their building surveyor through an acoustic consultant that no upgrades
or changes to the dwelling will be required.
However, waiting for the ‘shield houses’ to be constructed before you obtain your building permit
may not be practical. We expect that the majority of purchasers will want to build their new home
as soon as settlement occurs. This means that their house will be constructed before the shield
houses are built to lock up stage. It’s not possible for Westbrook to control exactly when all houses
are built. Because of this timing issue, our team has assumed that that your house will be
constructed first and as such it is best to assume that some acoustic treatment will be required to
your dwelling.
How does my builder confirm that my house complies with the acoustic requirement?
The noise coming from trains affecting bedrooms in your home will vary depending on:
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How far your house is from the rail line.
The level of the rail line near your home and the level of the ground around your home.
Any specific obstacles as well as any other major features such as the rail bridge at Skeleton
Creek or the future Morris Road over rail bridge between the rail line and the house.
The specific orientation of your house with respect to the rail line.
Whether the house is single or double storey.
At a more detailed dwelling and allotment level, the amount of noise coming into a bedroom within
a house is subject to several variables including:
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Sound insulation performance and surface area of the external walls. For example, light weight
or timber construction has a different noise performance that a brick veneer home.
Sound insulation and surface area of any windows and doors. Windows let in more sound than
an equivalent area of brick wall. This may mean that the glass on the windows may need to be
non-standard, for example requiring a thicker form of glass.
Sound insulation and surface area of the roof/ceiling (as applicable). Different forms of roofing
and insulation material in the roof will have a different acoustic performance.
Sound insulation and surface area of the floor. Different flooring materials, such as a concrete
slab or a wooden floor on stumps will have a different noise performance.
The impact of how windows and doors are sealed will impact the noise performance. This may
require a specific type of seal be used to ensure the noise requirement is met in the bedrooms.
The ratio of the floor area of the bedroom to the facade.
Due to these possible variables, your builder will need to obtain an acoustic report from a suitably
qualified consultant to confirm the particular requirements for your house on your lot. This report
will address the specific location of the house and its orientation on the lot and the specific built
form of the proposed house (i.e. single storey or double brick veneer construction). At that stage,
your builder will be able to confirm the particular building treatments required and advise you of the
proposed cost to construct your home.
Typical building requirements within the DDO at Westbrook
Westbrook’s acoustic consultants have undertaken acoustic modelling to determine the expected
typical requirements for a single storey brick veneer home to be constructed. The consultants
established in-principle construction requirements to assist stakeholders in understanding likely
implications of the restriction. However, these are only indicative and each dwelling will need its
own acoustic assessment. Two storey dwellings require additional assessment. In some cases,
lightweight construction on the second level will require an upgrade to brick veneer. This will have
an additional cost that needs to be understood and considered.
The Westbrook acoustic consultants established the typical or in-principle construction
requirements that may attenuate noise within bedrooms to not more than 65dB LAmax and 40 dB
LAeq, 8h for the night period from 10pm to 6am. Simply put, this means that the maximum noise
level must be kept below 65 decibels at all times and average noise levels kept to less than 50
decibels at night time. These construction requirements were found to generally be grouped and
assigned to one of two noise affected zones:
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Category 2: properties exposed to rail noise levels from 87 to 90dB LAmax
Category 3: properties exposed to rail noise levels less than 87dB LAmax
There are no Category 1 properties located on Westbrook. Category 2 typically applies to
houses on lots immediately abutting the rail line. Category 3 typically applies to the other lots within
the DDO. Most lots within the DDO are in Category 3.
Indicative treatment of Category 3 properties:
Facades of Category 3 bedrooms should have a weighted reduction index not less than Rw 52. This
may be achieved with brick veneer having a separate plasterboard lined stud. The stud cavity should
be filled with an insulating batt not less than 75mm thick.
Category 3 bedrooms should also be fitted with attenuated mechanical ventilation having a
weighted reduction index of not less than Rw35. An example of the mechanical ventilation can be
viewed at http://www.acoustica.com.au/aeropac.html. The unit is installed on a wall and plugged
into a supplied power point. It is simply a matter of switching the unit on when required. The home
owner can choose whether they wish to use the unit as they see fit. The unit has a filter, and that
will need to be replaced from time to time, depending on how often the unit is used by the
homeowner.
The ventilation unit must be maintained and retained in the bedroom and not removed.
It is possible to use other forms of air-conditioning, such as a split system air conditioner. Whether
this is cost effective for you will depend on the specific design of your proposed house, it may be
that a combination of a split system to address some bedrooms may be possible with mechanical
ventilation being used in other rooms. These are matters of detail that can be discussed with your
builder.
Indicative treatment of Category 2 properties:
Typical construction requirements for Category 2 properties are the same as that for Category 3 with
additional requirements for bedroom windows/external doors and roof/ceilings.
Window and external door systems of Category 2 bedrooms should have a weighted reduction index
not less than Rw 30. This may be achieved with the use of a single pane of 6.38mm thick laminated
glass, good quality aluminium extrusion and acoustic seals fitted to operable elements.
The roof/ceiling of Category 2 bedrooms should have a weighted reduction index not less than Rw
40. This may be achieved with a pitched 0.6mm thick steel deck roof over a plasterboard ceiling.
200mm insulation batts should be installed in the ceiling cavity. In addition, the eaves should be
boxed in using 6mm thick fibrous cement sheet.
Other design solutions may be acceptable and may be more or less cost effective, depending on the
specific design of your home.
Other questions and information
How do I know if these new acoustic requirements affect my lot?
The requirements are applied through a planning control called a Design and Development Overlay.
Where this overlay applies, a restriction will be inserted in the Plan of Subdivision. The requirements
affect most of the lots in Stages 10, 12 and 13. If your lot is affected, there will be a restriction and
indicative construction measures specified on the Plan of Subdivision.
Will the houses look different to other houses on Westbrook?
Generally, your home will look like any other house. The principal differences are each home in
Category 2 will be required to have an alternative form of glass in the bedroom windows and each
home within the DDO will require a ventilation system for bedrooms so that fresh air can circulate
when windows are closed. For example, if you are asleep with the windows closed to reduce noise
disturbance, then this ventilation feature allows fresh air to circulate into the bedroom.
What is the difference in the glass required in bedrooms of houses requiring acoustic treatment?
Does it look any different to normal glass? Can I open my windows as normal and leave them ajar in
summer if I wish to?
Standard glass is typically 3mm to 6mm thick. Category 2 lots requiring acoustic treatment, you
must have 6.38mm thick laminated glass installed in the bedrooms. Laminated glass has improved
sound insulation performance because of damping associated with the interlayer, which is a clear
film separating the two laminated layers of glass. The film is transparent so laminated glass doesn’t
look any different to normal glass. As you can see, the laminated glass is only slightly thicker than
normal glass.
You are able to open your bedroom windows as normal, just like any other house.
The laminate glazing must be maintained and retained in the bedroom windows (and doors if you
have glass doors) and cannot be removed.
What about the other rooms in my house? Why do they not receive noise attenuation measures?
The planning requirements have been developed to protect you from rail noise induced sleep
disturbance while in your bedroom. Your builder will need to ensure that your home is constructed
so your bedrooms meet the prescribed acoustic requirements. There is no requirement for other
rooms in your home to be upgraded so long as acoustic standards are met in your bedrooms.