The Role of a Designer – Analysis of the Thirroul Cliff House

Wednesday 2nd November, 2016

There was a recent article in the Illawarra Mercury¹ about a proposed development in the Thirroul area (not my design), that stirred a community uproar as they feared the effects of coastal erosion and impact the development could have on access and views from the neighbouring public reserve.

Examining this house provides a good opportunity to explain the role of designers in residential design, and the magnitude of policies and regulations that we need to be aware of and conform to for every house.

pexels-photo-128994
Council regulations ensure protection of our public views, areas and access for all

When planning to build your next home, clients need to be aware that they can’t just do anything on a block and need to meet a number of national and local standards – which should be the first thing to look at before planning their dream home, or even purchasing the block it is on.  Though I think the proposed cliff edge home is going to have a number of challenges, I also appreciate the position of the architectural company, who ultimately have to take design direction from their clients, even if they don’t necessarily agree that it will pass council planning and the associated bureaucracy.  The article has portrayed this project incorrectly (as the media do); though I will point out some concerns I would have regarding the project.

Home designs and designers need to be aware of entire volumes of regulations including:

1. The National Construction Code (NCC) – Volume 2
2. BASIX Requirements
3. Relevant Australian Standards
4. Local Environmental Plans
5. Development Control Plans
6. Authority Regulations

1The National Construction Code previously called the BCA, is fundamental to designers and it’s regulated to ensure that a home design meets the code’s requirements.  This applies to all homes state wide in a 200+ page volume.  The code restricts a number of aspects of the home, such as distance between structures before walls need to be fire rated, the openings required to rooms for ventilation and fire safety.  It is very difficult to vary from this documents requirements.

2BASIX requirements refer to minimum environmental performance of a dwelling. BASIX, or the Building Sustainability Index is a scheme developed by the New South Wales Government to regulate the energy efficiency of housing. Within BASIX a minimum score needs to be reached in three sections: thermal performance, water and energy.  The energy requirements are fairly easy to meet, whilst water is a little harder and usually requires a water tank.  The thermal performance, particularly the window subsections are the most challenging.  An interesting note is the less the number of bedrooms for a dwelling the more difficult it is to achieve a passing BASIX score.  When clients approach designers with home with an excessive number of windows, particularly on the east or west, it straight away rings alarm bells that the BASIX assessment is going to be difficult.


An interesting note is the less the number of bedrooms for a dwelling the more difficult it is to achieve a passing BASIX score.

3 The Australian Standards relate to the construction of a home, whereas the NCC governs design requirements. Designers need to be aware of the various Australian Standards so that they don’t design an aspect of the home that is otherwise impossible for a contractor to build to the requirements of the Australian Standards. For example, AS2047 details maximum window glass pane size based on site wind conditions.  As designer, if you specify a window larger than that practically achievable for the site, the window company is not going to be able to provide that window resulting in variation of the contract and design for the client.

4 Local Environmental Plans (LEPs) are related by local government areas, but typically governed by the state.  These plans define a number of site restrictions on a number of details maps.  These restrictions could be the zoning, with the permitted use of the lots defined, height restrictions, heritage and other site constraints.  It is difficult to vary at all from these requirements and they can impact significantly on what could be done on a site.  Whitehouse Concepts provides as a part of their free service an assessment of development lots regarding the LEP guidelines, but the best way to do this is to pay for a 149 certificate through council which defines site constraints.

5 Development Control Plans (DCPs) are local council requirements, and there can be a lot of them.  They define things such as setbacks from boundaries, the character of home as well as a whole host of other items.  These requirements are what’s assessed in detail during a development application.  DCP requirements can be varied, provided the design meets the fundamental objectives of the relevant section and there are no community objections raised.  For example council may require a street setback of 7m with the objective to maintain street character.  Your neighbours might only be set back 5m, so you could apply for a variation to 5m on the grounds that this is your neighbour’s setbacks and by reducing this setback, you’ll achieve the objective of street consistency.

6 The final regulations are authority requirements and the main one here is building over or near a sewer line.  In these circumstances, there is another whole set of guidelines that have to be met from Sydney Water that define what can and can’t be done in the vicinity of different water assets.  These guidelines aren’t usually negotiable.


So returning back to the Thirroul Cliff House, what would ring alarm bells for me is the foreshore building line, development near a coastline, BASIX, view sharing and geotechnical stability.

  • The LEP says development consent can’t be granted within the foreshore building line, unless for minor things. Referring to the council foreshore building line, they won’t likely be able to come any further forward towards the cliff than the existing house.
  • Coastline developments are a DCP requirements and specify things such as a 10m setback from the cliff line, which again this design might conform to.
  • There are lots of large windows to the East for a relatively skinny building, so the BASIX is going to be difficult and high performance glass, likely double glazed with a high shading co-efficient will be required.
  • View sharing is another DCP requirements and the proposed adversely impacts of views for adjacent property as well as it visually impacting the coastline, both of which will be difficult to justify.
  • Finally a detailed geotechnical assessment will be required to protect again coastal erosion.  This report is likely conclude with requirements of deep piers and foundations, which aren’t specifically a restraint, but will add significantly to the cost of construction.

Written by Michael Whitehouse (Facebook, Twitter, Linkedin)
Edited by Vivian Pham (Linkedin, Twitter)

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¹ http://www.illawarramercury.com.au/story/4250051/residents-on-edge-over-plans-for-thirroul-cliff-house/