Planning, Structural and Approval Considerations
Published: September 2026
Author: Adam Murphy – Principal Building Designer, ANS Design
Category: Residential Building Design | NSW Planning & Development
For many Sydney homeowners, moving is not necessarily the best way to gain more space.
When a property is in the right location but the existing house has become too small, adding a second storey — commonly referred to as a first-floor addition — can be an effective way of creating additional bedrooms, bathrooms and living areas while retaining valuable ground-level open space.
A well-designed first-floor addition can also transform the appearance and function of an older home without extending substantially further into the backyard.
However, building upwards introduces a different range of planning, structural and design considerations compared with a straightforward ground-floor extension.
Additional height can affect neighbouring properties through:
- overshadowing;
- privacy;
- visual bulk;
- solar access;
- views; and
- the relationship between buildings.
The existing dwelling must also be investigated to determine whether its walls, footings, framing and structural system are capable of supporting the proposed additional floor.
Before committing to a particular design, it is therefore important to investigate both the planning feasibility and structural implications of the project.
ANS Design provides residential building design, planning and development solutions across Sydney and NSW, including major alterations and additions, first-floor additions and residential approval documentation.
The practice is led by Adam Murphy, Principal Building Designer at ANS Design.
Why Add a Second Storey Instead of Extending at Ground Level?
On many suburban properties, available land is becoming increasingly valuable.
A large ground-floor extension may provide the additional internal space a family needs, but it can also reduce:
- landscaped area;
- private open space;
- garden area;
- swimming-pool opportunities;
- outdoor entertaining space; and
- natural light around the dwelling.
A carefully designed first-floor addition can avoid many of these problems.
For example, a new upper floor might contain:
- a master bedroom and ensuite;
- additional bedrooms;
- a family bathroom;
- a study;
- a parents’ or children’s retreat;
- storage; or
- balconies where the applicable planning controls permit them.
Moving bedrooms upstairs can also allow the ground floor to be substantially reorganised.
Former bedrooms might become part of:
- a larger kitchen;
- an open-plan living area;
- a dining room;
- a home office;
- a guest room;
- a butler’s pantry; or
- improved storage.
This means the project should not necessarily be thought of as simply putting another floor on the house.
It is an opportunity to reconsider how the entire home functions.
But before the floor plan is developed too far, one of the first questions should usually be:
Can the second-storey addition actually be approved?
In NSW, the two approval pathways most commonly relevant to residential alterations and additions are:
- Complying Development Certificate — CDC
- Development Application — DA
The NSW Government provides an overview of the different NSW planning approval pathways.
Determining the likely pathway early can significantly influence the eventual design.
Can a First-Floor Addition Be Approved Under CDC in NSW?
Potentially, yes.
The NSW Housing Code allows certain alterations and additions to existing dwelling houses to be undertaken as complying development where the land and the entire proposal satisfy the applicable requirements.
The controls are contained within the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008, commonly referred to as the Codes SEPP.
NSW Planning specifically identifies alterations and additions to dwelling houses as development that can potentially be undertaken under the Housing Code.
You can review the current NSW Government information here:
NSW Planning – Housing Code:
Housing Code and complying development requirements
A CDC combines planning and construction approval for qualifying development and can be determined by either a council or registered certifier.
However, CDC should not be thought of simply as a quicker DA.
It is fundamentally a standards-based approval pathway.
The development must comply with the relevant standards applying to the property and proposal.
For a first-floor addition, these may include requirements dealing with:
- zoning;
- lot dimensions;
- maximum building height;
- front setbacks;
- side setbacks;
- rear setbacks;
- upper-level setbacks;
- floor area;
- landscaped area;
- earthworks;
- privacy;
- building design;
- site constraints;
- bushfire considerations;
- flood considerations;
- heritage restrictions;
- environmentally sensitive land;
- other exclusions; and
- construction requirements.
NSW Planning currently states that the Housing Code applies within Zones R1, R2, R3, R4 and RU5.
However, being located within one of those zones does not automatically mean that a property qualifies for complying development.
The land and proposed works must satisfy all relevant requirements.
For further background on why these matters should be investigated before design begins, see:
Before You Design: NSW Planning Due Diligence – ANS Design
The 8.5-Metre Building Height Limit Under the Housing Code
Building height is one of the most important considerations when investigating a first-floor addition through the Housing Code.
Under the current Housing Code, the general maximum building height is:
8.5 metres
NSW Planning explains that building height is measured from the relevant existing ground level.
The Department actually uses a first-floor addition as an example when explaining how the 8.5-metre height control operates.
See:
NSW Housing Code – Building Height Requirements
This becomes particularly important on:
- sloping properties;
- properties that have previously been excavated;
- houses with elevated floor levels;
- sites containing retaining walls;
- designs with high ceilings;
- houses with substantial subfloor areas; and
- additions incorporating large pitched roofs.
A building may appear comfortably below the height control when viewed from the street but exceed it at another location where the natural ground level falls away.
For this reason, an accurate site survey is extremely important during the preliminary design stage.
The survey should generally establish information including:
- property boundaries;
- existing ground levels;
- existing floor levels;
- ridge levels;
- gutter levels;
- neighbouring development where relevant;
- retaining walls;
- significant trees;
- easements; and
- other important site features.
Building sections can then be developed through the proposed addition to properly assess the relationship between the proposed roof and existing ground levels.
Wall Height, Building Height and Side Setbacks Are Connected
Homeowners sometimes focus exclusively on the 8.5-metre overall building-height limit.
That is only part of the assessment.
Under the Housing Code, side setbacks can increase as the height of the building increases.
This is particularly important for first-floor additions.
An existing single-storey home might have walls relatively close to a side boundary.
That does not necessarily mean another storey can simply be constructed directly above those walls while remaining eligible for complying development.
The relationship between:
building height + lot width + boundary setback + upper-floor position
must be investigated.
This is one reason preliminary CDC assessment should occur before the architectural design of the upper floor is finalised.
A design may need:
- the upper floor stepped back from the ground-floor walls;
- changes to the roof form;
- different ceiling heights;
- a revised staircase position;
- additional articulation; or
- a reduced first-floor footprint.
The detailed Housing Code standards can be reviewed through the NSW Planning Portal:
What Happens If the First-Floor Addition Does Not Comply With CDC?
If a project cannot satisfy the applicable complying-development requirements, that does not necessarily mean the first-floor addition cannot proceed.
A Development Application may instead be required, subject to the development being permissible and capable of satisfying the relevant planning assessment.
NSW Planning explains the DA process under its:
Local Development and Development Application information
A DA is generally assessed against the broader planning framework applying to the property.
This can include:
- the relevant Local Environmental Plan — LEP;
- the relevant Development Control Plan — DCP;
- applicable State Environmental Planning Policies;
- the Environmental Planning and Assessment framework;
- site-specific constraints;
- environmental impacts;
- neighbouring amenity; and
- the character of the locality.
Council controls vary significantly across NSW.
A first-floor addition in Ryde may therefore face different controls from a similar project in:
- Parramatta;
- Willoughby;
- Inner West;
- Northern Beaches;
- Penrith;
- Blacktown;
- The Hills;
- Hawkesbury;
- Central Coast; or
- Newcastle.
Typical council controls affecting first-floor additions can include:
- maximum building height;
- floor space ratio;
- site coverage;
- landscaped area;
- deep-soil requirements;
- front setbacks;
- side setbacks;
- rear setbacks;
- upper-storey setbacks;
- wall height;
- building envelopes;
- privacy requirements;
- solar-access requirements;
- streetscape character; and
- heritage considerations.
ANS Design assists with both DA and CDC documentation and residential building design.
CDC or DA? The Best Pathway Depends on the Property
Homeowners sometimes begin a project assuming that CDC must automatically be the better option because it can potentially provide a faster approval process.
That is not always the case.
For some properties, CDC provides an excellent pathway.
For others, attempting to force the project into prescriptive complying-development controls may compromise the design unnecessarily.
A DA may sometimes provide a more suitable planning and architectural response.
The more useful question is therefore not simply:
“Can I get a CDC?”
It is:
“Which approval pathway is most appropriate for this particular property and proposed design?”
This is why early planning investigation can be valuable.
ANS Design discusses this process in more detail in:
Before You Design: NSW Planning Due Diligence
What About the Proposed CDC Variation System?
NSW has also been progressing reforms that may provide limited flexibility for some complying-development standards.
However, homeowners should not assume that a non-compliant first-floor addition can automatically obtain a variation.
The scope and operation of any variation mechanism needs to be checked against the legislation actually in force when an application is prepared.
ANS Design has covered the proposed changes in detail here:
Can a CDC Be Varied in NSW? Proposed Changes Explained
This is particularly relevant where a proposal comes close to a complying-development standard but does not completely satisfy it.
Until the relevant pathway is legally available and applicable to the particular standard involved, a project should not be designed on the assumption that a variation will be available.
Overshadowing Becomes More Important When Building Upwards
One of the most significant differences between a ground-floor extension and a first-floor addition is the potential impact on neighbouring sunlight.
Adding another level can create longer shadows over adjoining properties.
Depending on the relevant council controls, shadow diagrams may be required to demonstrate the effect of the proposed development on:
- neighbouring living-room windows;
- neighbouring private open space;
- the subject property’s own private open space;
- solar access to dwellings; and
- potentially other solar-sensitive areas.
Shadow diagrams are commonly assessed around the winter solstice — 21 June, when solar access is at its most constrained.
Depending on the relevant council’s requirements, diagrams may show shadows at times such as:
- 9:00 am;
- 12:00 noon; and
- 3:00 pm.
The exact requirements depend on the relevant planning controls.
Good design can often substantially reduce overshadowing through decisions involving:
- upper-floor positioning;
- wall height;
- roof pitch;
- increased setbacks;
- articulation;
- building orientation; and
- locating the higher portions of the building away from sensitive boundaries.
Solar analysis should therefore help shape the design rather than being treated simply as a drawing prepared at the end of the DA process.
Privacy Between Neighbouring Properties
Privacy is another significant consideration when adding an upper floor.
A ground-floor window may be naturally screened by:
- boundary fencing;
- landscaping;
- existing walls; or
- surrounding structures.
A first-floor window can look directly over those elements.
Particular attention should therefore be given to upper-storey windows overlooking:
- neighbouring living areas;
- bedrooms;
- swimming pools;
- decks;
- courtyards; and
- private open space.
Privacy does not necessarily mean eliminating windows.
Appropriate design responses might include:
- raising sill heights;
- using highlight windows;
- relocating windows;
- offsetting windows from neighbouring openings;
- translucent glazing where appropriate;
- fixed privacy screens;
- careful room planning; and
- carefully positioning balconies.
The objective is generally to provide appropriate natural light and ventilation while avoiding unreasonable overlooking.
This demonstrates an important principle of successful first-floor design:
The design needs to consider what is happening outside the property as well as inside it.
The Existing House Must Be Able to Support the Addition
Planning approval is only one part of a successful first-floor addition.
A new storey introduces substantial additional loads into an existing structure.
Depending on its age and construction, an existing house may contain:
- brick veneer walls;
- double-brick or cavity-brick construction;
- timber wall framing;
- steel framing;
- concrete slabs;
- suspended timber floors;
- strip footings;
- brick piers;
- concrete piers; or
- combinations of structural systems created through previous renovations.
The original dwelling may have been designed decades ago without any intention of supporting another floor.
A structural engineer may therefore need to investigate matters including:
- existing footings;
- load-bearing walls;
- structural framing;
- beams;
- floor structures;
- roof framing;
- soil conditions; and
- proposed load paths.
Depending on the existing structure, additional work may be required, such as:
- new beams;
- new columns;
- wall strengthening;
- new framing;
- underpinning;
- new pad footings; or
- additional support structures extending through the existing building.
Structural work can have a significant impact on the construction budget.
For this reason, structural feasibility should be considered during the design process rather than discovering substantial strengthening requirements after the architectural documentation has already been completed.
Lightweight First-Floor Construction
Many first-floor additions use comparatively lightweight construction.
Depending on the project, this may include:
- timber framing;
- lightweight steel framing;
- fibre-cement cladding;
- lightweight wall systems; and
- lightweight roofing materials.
Reducing the weight of the proposed addition can sometimes assist when working with an existing structure.
It can also provide an opportunity to create an architectural distinction between the original dwelling and the new addition.
However, material selection should consider much more than weight.
Other issues include:
- structural performance;
- fire performance;
- acoustic performance;
- thermal performance;
- durability;
- maintenance;
- weatherproofing;
- waterproofing;
- neighbourhood character; and
- NCC requirements.
Structural design, architectural design and construction methodology therefore need to be coordinated as the project progresses.
Staircase Placement Can Determine Whether the Floor Plan Works
One of the most underestimated aspects of adding a second storey is the staircase.
A staircase consumes more space than many homeowners initially expect.
More importantly, it affects both levels of the dwelling simultaneously.
On the ground floor, the staircase can affect:
- hallways;
- bedrooms;
- bathrooms;
- living rooms;
- kitchens;
- entrances; and
- circulation.
On the upper floor, the stair position immediately influences:
- landings;
- corridors;
- bedroom positions;
- bathrooms;
- storage; and
- overall usable floor area.
Poor staircase placement can result in a substantial percentage of the new floor area being consumed by corridors.
A well-positioned staircase can instead become the organising element around which the entire renovation is designed.
Important considerations include:
- stair width;
- head clearance;
- rise and going;
- landings;
- balustrades;
- structural openings;
- access to natural light;
- existing circulation; and
- avoiding unnecessary hallway space.
Sometimes moving a staircase by a relatively small distance can substantially improve both levels of the home.
The staircase should therefore generally be considered at the beginning of the concept design process, rather than being inserted after all the upstairs rooms have already been planned.
Don’t Design Only the New Floor
One of the greatest opportunities created by a first-floor addition is the ability to reconsider the existing house.
Rather than simply adding bedrooms upstairs, the project can often improve the whole dwelling.
Moving sleeping accommodation to the upper level may free existing ground-floor rooms for:
- larger living spaces;
- a home office;
- a guest bedroom;
- a bigger kitchen;
- a butler’s pantry;
- laundry improvements;
- storage; and
- stronger connections to outdoor areas.
The objective should generally be:
Design the existing house and the new addition as one home.
The best second-storey additions often feel as though the completed dwelling was designed as a whole rather than appearing as though a separate building has simply been placed on top.
You can see examples of completed ANS Design alteration and addition projects on the:
Two additional examples are:
Epping Alteration & Addition – ANS Design
Islington Alteration & Addition, Newcastle – ANS Design
Roof Design Matters
The roof can have a substantial influence on whether a first-floor addition looks balanced or oversized.
Possible design approaches include:
- pitched roofs reflecting the existing dwelling;
- lower-pitched contemporary roofs;
- hipped roofs;
- gable forms;
- skillion roofs; and
- combinations of different forms.
Roof design influences:
- overall building height;
- wall height;
- streetscape presentation;
- solar access;
- stormwater drainage;
- internal ceiling volume; and
- construction complexity.
This becomes particularly important where the project is approaching a statutory building-height limit.
A roof that works aesthetically in isolation may create unnecessary planning difficulties if it adds excessive height.
The roof should therefore be considered as part of both the architectural design and planning strategy.
BASIX and Energy Efficiency
A significant first-floor addition will also usually need to consider NSW sustainability requirements.
Current NSW Planning information states that BASIX applies to alterations and additions to residential dwellings where the project cost is $50,000 or more, as well as certain other residential development.
More information is available from:
BASIX can influence matters including:
- insulation;
- glazing;
- window sizes;
- window orientation;
- shading;
- hot-water systems;
- ventilation;
- energy performance; and
- other sustainability commitments.
Once a BASIX certificate forms part of the approved documentation, the relevant commitments must be reflected in the project documentation and construction.
ANS Design has also prepared a detailed guide explaining BASIX:
BASIX in NSW: How It Impacts Your Home Design
Why Preliminary Planning Advice Is Important
One of the most expensive mistakes in residential design is developing an advanced concept before determining whether the fundamental planning parameters work.
Before committing to a first-floor addition, a preliminary assessment can investigate questions including:
- What is the zoning?
- Is the Housing Code available for the property?
- Are there heritage restrictions?
- Is the land flood affected?
- Is the site bushfire affected?
- What is the maximum building height?
- What setbacks apply?
- How much first-floor area can realistically be achieved?
- Does the position of the existing house create CDC setback problems?
- Is a DA likely to provide a better pathway?
- Could overshadowing become a major planning issue?
- Where can upper-storey windows be positioned?
- Are there easements or other site constraints?
- Is the existing dwelling arrangement suitable for a practical staircase?
These questions can substantially influence what should ultimately be designed.
Spending time on planning due diligence at the beginning can help avoid larger redesign costs later.
For a detailed explanation of the early planning process, see:
Before You Design: NSW Planning Due Diligence – Adam Murphy, ANS Design
A Real ANS Design Example: Putney Alterations and First-Floor Addition
A good example of the opportunities presented by building upwards is the Putney alterations and first-floor addition project undertaken by ANS Design.
The project involved substantial alterations to the existing dwelling together with the creation of a new first-floor level.
Rather than treating the new floor as an isolated extension, the project considered how the existing and proposed areas could work together as a complete home.
This type of design approach can provide significantly more internal accommodation while retaining valuable ground-level outdoor space.
It also demonstrates an important principle of successful residential alterations:
The objective is not simply to make a house larger — it is to make the whole home work better.
View ANS Design’s completed residential work here:
ANS Design Building Design Projects
A Typical First-Floor Addition Design and Approval Process
While every property is different, the process may broadly involve the following stages.
1. Preliminary Planning Investigation
Review the property’s planning controls, constraints and potential approval pathways.
This can include:
- zoning;
- LEP controls;
- DCP controls;
- Codes SEPP requirements;
- heritage;
- bushfire;
- flooding;
- easements; and
- other site-specific constraints.
Read more about preliminary NSW planning due diligence.
2. Site Survey
Obtain an accurate survey showing boundaries, levels and existing development.
For a first-floor addition, vertical information is particularly important because it assists with assessing:
- building height;
- roof height;
- setbacks;
- neighbouring relationships; and
- shadow impacts.
3. Existing Building Documentation
Where accurate original drawings are unavailable, the existing dwelling may need to be measured and documented.
This establishes a reliable base from which the alteration and addition can be designed.
4. Concept Design
Potential solutions can then be developed for:
- staircase position;
- upper-floor layout;
- ground-floor alterations;
- external appearance;
- roof form;
- windows;
- privacy; and
- indoor-outdoor relationships.
5. Planning Review
The evolving design should then be checked against the relevant:
- CDC controls; or
- council LEP and DCP requirements.
Planning and design should ideally occur together rather than treating compliance as something that is checked only after the design is finished.
6. Structural Investigation
A structural engineer may be engaged to assess:
- the existing building;
- proposed load paths;
- structural feasibility; and
- any strengthening requirements.
7. Detailed Design and Documentation
Plans, elevations, sections and supporting documentation can then be prepared for the relevant approval pathway.
ANS Design provides:
Residential Building Design, DA, CDC and Approval Documentation
8. Consultant Coordination
Depending on the property and project, consultants may include:
- structural engineers;
- surveyors;
- BASIX/NatHERS assessors;
- stormwater engineers;
- arborists;
- bushfire consultants;
- geotechnical engineers; and
- other specialists.
9. DA or CDC Submission
The completed documentation can then be lodged through the appropriate pathway.
For information about Development Applications:
NSW Planning – Local Development and DA Process
For information about complying development:
For an overview of both pathways:
NSW Planning Approval Pathways
Before You Start Designing a Second Storey
If you are considering adding another level to your home, some of the most useful information to establish early includes:
- the property’s planning controls;
- an accurate survey;
- the dimensions of the existing dwelling;
- the construction and condition of the existing house;
- the rooms your household actually requires;
- how the existing ground floor could be improved;
- likely structural implications; and
- the approximate construction budget.
Try not to begin with a fixed assumption that the new floor must contain a particular number of bedrooms or achieve a predetermined floor area.
Instead, determine what the site, planning controls, existing structure and household requirements can reasonably accommodate.
The resulting design is often substantially better.
Planning a First-Floor Addition in Sydney or NSW?
Adding a second storey can completely transform an existing home, particularly on properties where preserving backyard and landscaped area is important.
But a successful first-floor addition requires more than simply designing an attractive new upper level.
The project needs to consider:
- the appropriate planning approval pathway;
- building height;
- wall height;
- side and rear setbacks;
- overshadowing;
- neighbouring privacy;
- structural capacity;
- staircase design;
- roof form;
- sustainability;
- buildability; and
- the relationship between the existing and proposed dwelling.
Early investigation can identify potential planning and structural issues before substantial time and money are committed to detailed design.
ANS Design provides Building Design, Planning & Development Solutions across Sydney and NSW, including:
- alterations and additions;
- first-floor additions;
- new homes;
- secondary dwellings;
- DA documentation;
- CDC documentation;
- Construction Certificate documentation;
- BASIX and NatHERS coordination;
- planning and compliance advice; and
- consultant coordination.
Explore:
ANS Design – Building Design, Planning & Development Solutions
About Adam Murphy – Principal Building Designer
About Adam Murphy
Adam Murphy is the Principal Building Designer at ANS Design, a Sydney-based residential building design practice providing design, planning and approval documentation across Sydney and NSW.
Adam works directly with homeowners, builders and property owners on residential projects including alterations and additions, first-floor additions, new homes, secondary dwellings and approval documentation.
Learn more:
About Adam Murphy – ANS Design
Important Note
The information in this article is general in nature.
Planning and building requirements vary according to the property, local government area, zoning, site constraints, approval pathway and proposed design.
The fact that another first-floor addition has been approved under CDC or through a Development Application does not mean that the same pathway will necessarily apply to another property.
Current legislation, mapping and site-specific controls should always be reviewed before substantial design work is undertaken.
Useful Links and Resources
ANS Design
ANS Design Home
https://ansdesign.com.au/
Building Design Services
https://ansdesign.com.au/building-design-services-sydney/
Completed Building Design Projects
https://ansdesign.com.au/building-design-projects-sydney/
Adam Murphy – Principal Building Designer
https://ansdesign.com.au/about-adam-murphy/
ANS Design Service Areas
https://ansdesign.com.au/service-areas/
Contact ANS Design
https://ansdesign.com.au/contact-building-designer-sydney/
Before You Design: NSW Planning Due Diligence
https://ansdesign.com.au/nsw-planning-due-diligence-da-cdc/
Can a CDC Be Varied in NSW?
https://ansdesign.com.au/can-a-cdc-be-varied-in-nsw/
BASIX in NSW: How It Impacts Your Home Design
https://ansdesign.com.au/what-is-basix-nsw-design/
Epping Alteration & Addition Project
https://ansdesign.com.au/projects-alteration-addition-epping-nsw/
Islington Alteration & Addition Project
https://ansdesign.com.au/projects-islington-alteration-addition-newcastle/
NSW Government
NSW Housing Code
https://www.planningportal.nsw.gov.au/development-assessment/codes-sepp/housing-code
NSW Planning Approval Pathways
https://www.planningportal.nsw.gov.au/development-and-assessment/planning-approval-pathways
Development Applications / Local Development
https://www.planningportal.nsw.gov.au/onlineDA
BASIX
https://www.planningportal.nsw.gov.au/basix/about-basix
BASIX and Planning Approvals
https://www.planningportal.nsw.gov.au/basix/about-basix/BASIX-and-planning-approvals
NSW Planning Portal
https://www.planningportal.nsw.gov.au/
NSW Legislation
https://legislation.nsw.gov.au/
Disclaimer: This article provides general information about planning and building requirements in NSW as at September 2026. Requirements may change and individual properties may be subject to additional planning, building, environmental, title or infrastructure restrictions. The information should not be relied upon as confirmation of development eligibility or approval. Project-specific planning, building and consultant assessments should be undertaken before proceeding.
Adam Murphy
Principal Building Designer
ANS Design
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