In NSW, retaining walls can fall into one of three approval categories: exempt development (no approval needed), complying development (fast-track approval via a certifier, not council), or development application (full council DA process). Which category applies depends on the height of the wall, the location, any overlays on the land, and specific conditions in the state and local planning instruments.
The bottom line: most retaining walls in the Blue Mountains LGA up to 1.0 metre retaining height can be approved as complying development, provided they meet all the qualifying conditions. Heritage conservation areas, cliff zones, and drainage line proximity can exclude a wall from complying development even when it meets the height threshold.
The Three Tiers of Approval
Tier 1: Exempt Development, No Approval Needed
Under the NSW State Environmental Planning Policy (Exempt and Complying Development Codes) 2008, retaining walls meeting all the following conditions are exempt development:
- Maximum 600mm in height
- Not within an environmentally sensitive area
- Not within 1.0 metre of a drainage line, easement, or watercourse
- Not within a heritage item or in a heritage conservation area where the wall would be visible from a public road
- Not within a cliff zone or near an escarpment
- Not associated with a swimming pool
If all those conditions are met, you can build the wall without any approval, certification, or council contact. A licensed builder or owner-builder can construct it.
Tier 2: Complying Development, Fast-Track Approval
Complying development (CD) is available for retaining walls that don’t qualify as exempt but meet the standards in the Exempt and Complying Development Codes SEPP. A complying development certificate (CDC) is issued by a private accredited certifier, not by BMCC, and approval typically takes 10-20 business days.
Typical qualifying conditions for retaining wall CD:
| Criterion | Standard Requirement |
|---|---|
| Maximum height | Generally 1.0m |
| Setback from drainage line | Typically 1.0m minimum |
| Setback from watercourse | As specified (often 5-10m) |
| Heritage conservation area | Generally excluded |
| Cliff zones / escarpment | Generally excluded |
| Bushfire prone land | May have additional conditions |
| Land category | Standard residential, not environmental protection zones |
Note that complying development standards can change with amendments to the SEPP. Always verify the current standards with your certifier or at [/guides/bmcc-council-approval-retaining-walls/].
Tier 3: Development Application, Full Council Process
A DA through BMCC is required when the wall doesn’t qualify as exempt or complying development. This includes:
- Walls over 1.0m retaining height
- Walls in heritage conservation areas visible from the public domain
- Walls near cliff edges or escarpment zones
- Walls near drainage lines or watercourses where setback cannot be achieved
- Walls in environmental protection zones
- Walls associated with other development that already requires a DA
A DA process at BMCC typically takes 40-90 days, requires preparation of plans and supporting documents, and costs council assessment fees in addition to any consultant fees. See [/guides/bmcc-development-application-retaining-walls/] for the full DA guide.
BMCC-Specific Complications
The Blue Mountains LGA has several overlays and local conditions that frequently push walls out of the complying development tier even when height thresholds appear to be met.
Heritage Conservation Areas (HCAs)
BMCC has extensive heritage conservation areas, particularly in Katoomba, Leura, Blackheath, Mount Victoria, and Springwood. Retaining walls visible from a public road within an HCA are typically excluded from complying development, they require a DA, often with a heritage impact statement.
To check whether your property is in an HCA, use the BMCC mapping portal or the NSW Planning Portal lot search. If you’re in an HCA, assume you need a DA for any wall over 600mm that can be seen from the street.
Cliff Zones and Escarpment Controls
Properties within 40 metres of a cliff edge or escarpment face additional controls that generally preclude complying development for any significant earthworks. Wentworth Falls, Katoomba, Leura, and Blackheath all have extensive cliff zone areas.
Drainage Lines
BMCC’s development control plans map drainage lines across the LGA, and setback requirements from these lines are strict. A wall within 1.0 metre of a mapped drainage line will typically not qualify for CD. In practice, many Blue Mountains properties have drainage lines running through or near their boundaries, always check the BMCC mapping before assuming CD is available.
Bushfire Prone Land
Blue Mountains properties are extensively mapped as bushfire prone land. Some bushfire areas don’t affect complying development eligibility for retaining walls, but BAL-FZ (flame zone) and some BAL-40 sites may trigger exclusions. Consult the NSW Rural Fire Service maps and check with your certifier.
Geotechnical Hazard Areas
Areas with potential geotechnical hazards (unstable slopes, landslip risk, subsidence) may also exclude complying development. The Blue Mountains has significant areas with these constraints given the terrain.
The Complying Development Certificate Process
If your wall qualifies for CD, here’s how the process works:
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Engage a private accredited certifier, not BMCC. A certifier (also called a PCA, principal certifying authority) will assess your proposal against the complying development standards.
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Prepare documentation, typically: a site plan showing wall location and dimensions, wall type and construction details (drawings), drainage plan, and a basic site analysis.
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Certifier assessment, the certifier checks the proposal against all qualifying conditions. If everything meets the standards, a CDC is issued. Typically 10-20 business days.
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Commence work, work can commence after the CDC is issued. The certifier will likely need to carry out one or more inspections during construction (drainage, footings, final).
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Final occupation certificate (if required), for walls associated with other development, an occupation certificate may be needed at completion.
Estimated cost of CD process: Certifier fees for a residential retaining wall CDC typically range from $800 to $2,500 depending on the complexity of the documentation required.
What Needs to Be in the Plans
Whether you’re applying for CD or a DA, the documentation needs to show:
| Document | Typical Requirement |
|---|---|
| Site plan | Wall position, setbacks from boundaries and drainage lines, topography |
| Wall drawings | Cross-section showing height, materials, H-post size and spacing, footing depth |
| Drainage plan | Ag pipe location, gradient, outlet point |
| Engineering certificate | Required for walls over 1.0m and some lower walls |
| Geotechnical report | Required for walls near escarpments, drainage lines, steep slopes |
| Heritage impact statement | Required if in heritage conservation area |
For walls that require a DA, BMCC’s pre-DA advice service is valuable, a 15-minute call to the duty planner can clarify what documents are needed and flag any issues before you spend money on plans. See [/guides/bmcc-development-application-retaining-walls/] for the DA process guide.
Do I Need an Engineer for Complying Development?
Engineering certification is not always mandated for complying development retaining walls, but it is strongly recommended for any wall that:
- Approaches the maximum qualifying height (e.g., 900mm, 1.0m retaining)
- Is above a structure, driveway, or vehicle area
- Has significant soil loads from steep upslope ground
- Is on a site with uncertain soil conditions
Even without a DA, your builder or you as the owner can face liability if a non-engineered wall fails and causes damage. An engineer’s certificate shifts that liability appropriately and ensures the wall is designed to carry the actual loads.
See [/guides/engineer-certificate-retaining-wall/] for detail on engineering certification.
Common Mistakes That Invalidate Complying Development
Projects sometimes proceed as complying development and then face enforcement action from BMCC because:
- The property was in an HCA and the wall was visible from the road, DA was actually required
- The wall height was measured incorrectly, 1.0m is the maximum retaining height (difference between retained ground level and finished surface on the low side), not the visible face height
- The drainage line setback wasn’t checked on BMCC maps, the wall was within the setback
- The site had a heritage item in the vicinity triggering controls the owner wasn’t aware of
Always do the due diligence before starting work. See [/guides/bmcc-consent-retaining-wall-thresholds-overview/] for the threshold overview.
FAQ
Can a certifier approve my retaining wall, or does it have to go to BMCC? Yes, complying development is approved by a private accredited certifier (not BMCC council). This is usually faster and sometimes cheaper than a DA. The certifier must be registered with the NSW Building Professionals Board.
How long does complying development approval take in the Blue Mountains? A CDC for a retaining wall typically takes 10-20 business days once the certifier has all the required documents. This is faster than a DA, which runs 40-90 days through BMCC.
If I’m in a heritage conservation area, do I always need a DA? Walls visible from the public road in a heritage conservation area generally require a DA. Walls at the rear of the property not visible from the street may still qualify as exempt or complying development, check with BMCC or a certifier for your specific situation.
What happens if I build without approval when one was needed? BMCC can issue a stop-work order, require demolition and reinstatement, and issue fines. Unapproved structures can also cause difficulties when selling the property. It’s always cheaper to get approval first. See [/guides/diy-retaining-walls-nsw-rules/].
Can Blue Mountains Retaining Walls help me navigate the approval process? Yes. Your enquiry can be referred to a contractor who works through both the complying development and DA process, and we can point you to certifiers and heritage consultants experienced with BMCC requirements.
Get expert guidance on your retaining wall approval, contact us at /contact/#quote