BMCC Development Applications for Retaining Walls: A Step-by-Step Overview

Navigating Blue Mountains City Council’s development consent process for a retaining wall is one of the more common sources of delay and cost overruns on Mountain properties. The rules are more complex than they appear, what qualifies as exempt development on a flat Penrith lot may require a full DA in Leura or Blackheath, especially in heritage conservation areas or close to the World Heritage Area boundary. This guide walks through the process so you know what to expect before you start.

Quick answer (BLUF)

Most retaining walls under 600mm high on residential land qualify as exempt development and need no council approval. Walls 600mm, 1,000mm may qualify for complying development. Anything taller, in a heritage conservation area, near a watercourse, on bushfire-prone land or within a World Heritage buffer zone will generally require a full development application. Heritage overlay properties require extra documentation regardless of height.

Exempt development: no approval needed

Under the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008, commonly called the Codes SEPP, certain retaining wall works are exempt from development consent. The standard criteria include:

• Wall height not exceeding 600mm above natural ground level
• Wall is not within 1 metre of a building or swimming pool
• Wall does not redirect stormwater onto an adjoining property
• Wall is not in a heritage conservation area, draft HCA, or World Heritage Area buffer
• Land is not classified as a flood control lot or critical habitat

In the Blue Mountains, heritage conservation areas cover large portions of Katoomba, Leura, Blackheath and Wentworth Falls. Check your property’s status on BMCC’s online mapping tool (BMaps) before assuming your project is exempt.

Complying development: fast-track approval

For walls between 600mm and 1,000mm that meet the Codes SEPP criteria for complying development, a private certifier can issue a complying development certificate (CDC) without a BMCC DA. This is significantly faster, typically 10-20 days versus 40-80 days for a DA.

Complying development is not available where:

• The wall is in a heritage conservation area
• The site has a heritage listing on the State Heritage Register
• The wall is in a World Heritage Area buffer zone
• The site is within a critical habitat or environmentally sensitive area
• The wall exceeds 1,000mm in height

Many Blue Mountains properties sit in one or more of these categories. If in doubt, a pre-lodgement meeting with BMCC’s development assessment team is free and can clarify your pathway quickly.

When a full DA is required

A development application is required for any retaining wall that:

• Exceeds 1,000mm in height
• Is in a heritage conservation area (regardless of height)
• Is on a heritage-listed property
• Is within 40 metres of a watercourse
• Is on land with a slope steepening clause trigger (common on escarpment lots)
• Forms part of a larger earthworks proposal exceeding BMCC’s exempt thresholds

A DA through BMCC typically takes 40-80 working days from lodgement. Complex proposals involving heritage, flooding, or biodiversity may take longer. You will need:

1. A site plan prepared by a surveyor or draftsperson showing the wall location, height, setbacks and levels
2. A structural engineer’s detail drawing and certificate
3. A BASIX certificate if the retaining wall is part of a broader residential development
4. A statement of environmental effects (SEE)
5. For heritage properties: a heritage impact statement prepared by an accredited heritage consultant

Heritage conservation areas in the Blue Mountains

BMCC heritage conservation areas include significant portions of Katoomba, Leura, Blackheath, Mount Victoria and Lawson. In these areas, retaining wall materials must generally be consistent with the heritage character of the streetscape. Sandstone dry-stone walls and coursed sandstone are typically acceptable; exposed concrete block and galvanised steel posts may require justification.

The heritage impact statement must assess whether the proposed wall is sympathetic to the conservation area’s character, scale and materials palette. This adds $1,500 to $4,000 to the application cost but is non-negotiable in heritage-listed areas. See our guide to heritage conservation and retaining wall materials for detail on what BMCC accepts.

World Heritage Area buffer zone constraints

The Greater Blue Mountains World Heritage Area boundary runs close to developed parts of Katoomba, Leura, Blackheath and Mount Victoria. Within the buffer zone, earthworks are subject to additional scrutiny under both the Blue Mountains Local Environmental Plan 2015 and federal environmental law. Retaining walls that involve significant vegetation removal, drainage alteration or earthwork within the buffer zone may trigger a referral to the NSW Department of Planning and Environment.

Check your lot’s proximity to the WHArea boundary on BMaps before proceeding. Even lots that appear well within the urban area can sit within the buffer zone.

Practical tips for a faster approval

• Start with BMaps: check for heritage overlays, flood planning, biodiversity values and WHArea buffers before engaging a contractor
• Request a pre-lodgement meeting: BMCC officers will advise on what’s required before you spend money on plans
• Use a town planner or certifier: for borderline or complex sites, a $500 to $1,000 investment in planning advice can save weeks of back-and-forth
• Keep the wall below the key thresholds: if your design flexibility allows, a 590mm wall saves a DA; a 950mm wall may allow a CDC rather than a DA
• Engage a heritage consultant early: for HCA properties, their input should shape the design before you submit, not after BMCC rejects your first proposal

FAQs

Can my builder get the DA, or do I need to do it?

Either you or your builder can lodge the DA as the applicant, but the property owner is ultimately responsible for compliance. Most retaining wall contractors in the Blue Mountains either handle the DA themselves or work with a preferred certifier. Confirm this in writing before signing a contract.

How long does BMCC take to approve a retaining wall DA?

The statutory timeframe is 40 working days (about 8 weeks) for a standard residential DA. In practice, many BMCC applications take 10-14 weeks due to referrals and information requests. Factor this into your project timeline.

Do I need development consent for a replacement retaining wall?

If you are replacing a like-for-like wall of the same height and material, you may be able to argue the work is maintenance rather than new development. This depends on the site’s planning controls. A conversation with BMCC or a certifier before demolition is strongly recommended, removing an existing wall and rebuilding it to the same specification still triggers consent if it is in a heritage conservation area.

What happens if I build a retaining wall without consent?

BMCC can issue a stop-work order, a penalty infringement notice, and may require the wall to be demolished and reinstated with consent. Unauthorised retaining walls can also complicate property sales, conveyancers routinely check for unapproved structures.