The Blue Mountains has one of the most extensive networks of heritage conservation areas in regional NSW. Katoomba, Leura, Blackheath, Wentworth Falls, Lawson and Springwood all have designated heritage conservation areas (HCAs) that protect the streetscape character, materials palette and architectural scale of these mountain towns. For retaining walls, particularly those visible from public land, the HCA designation significantly affects what materials and construction approaches BMCC will accept.
Getting material selection right from the outset is far more efficient than building in inappropriate materials and facing a BMCC refusal or enforcement action.
Quick answer (BLUF)
In Blue Mountains heritage conservation areas, retaining walls visible from public land are generally required to use natural stone, primarily sandstone, consistent with the existing heritage character. Concrete sleeper walls and exposed galvanised steel posts are typically unacceptable. Brick, in traditional bond, may be acceptable on properties where brick is the heritage vernacular. Lime mortar (or appropriately coloured cement mortar) is preferred over standard grey cement mortar. A heritage impact statement is required for all retaining wall DAs in HCAs.
Why heritage conservation areas apply such strict material requirements
The heritage value of Blue Mountains towns lies substantially in their landscape character, the combination of sandstone buildings, dry-stone walls, formal Victorian-era gardens, and the bush backdrop. These towns were developed by Sydneysiders of means during the late 19th and early 20th centuries, and the legacy is an unusually coherent streetscape of stone walls, terracotta roof tiles, Arts and Crafts details and deep garden setbacks.
Inappropriate materials, modern concrete products, metallic cladding, exposed galvanised steel, disrupt this character visually in a way that individual small-scale changes can collectively have significant cumulative impact. BMCC’s heritage controls aim to prevent this cumulative erosion of character.
Accepted materials by context
Front boundaries and visible street-facing walls
Strongly preferred: Coursed or dry-laid Hawkesbury sandstone, matching the colour and texture of the dominant stone in the surrounding streetscape. Local quarried sandstone has a distinctive warm grey to honey buff colour that characterises Blue Mountains heritage construction.
Acceptable: Dressed sandstone with lime mortar pointing in a traditional bond; dry-stone sandstone in the local vernacular tradition; other natural stone consistent with local character (rare in the Blue Mountains).
Conditionally acceptable: Brick, where the property’s heritage character is brick-dominant and the new wall is consistent with the existing brick type, bond and mortar colour; rendered masonry where the property is heritage-listed with rendered masonry elements.
Generally unacceptable: Concrete sleepers, concrete block (unless rendered to match), exposed galvanised or coloured steel posts, aluminium, modern cladding materials.
Rear and internal walls not visible from public land
BMCC applies less stringent requirements to walls not visible from the street or public land. Concrete sleepers, besser block and other modern materials may be acceptable in these locations, provided drainage and other technical requirements are met. The heritage impact statement should clearly describe the visibility context of each wall.
Mortar specification in heritage areas
The mortar used in heritage sandstone walls is as important as the stone. Standard Portland cement mortar (the grey or off-white mortar common in modern construction) is often visually incompatible with the original lime-based mortars used in heritage construction. Lime mortar has a lighter, warmer colour and different surface texture that blends more naturally with sandstone.
Lime mortar also has physical advantages in heritage work: it is softer and more flexible than Portland cement mortar, reducing stress cracking in the adjacent stone; it is more porous, allowing the wall to breathe and dry after rainfall; and it can be repointed without damaging the stone face.
BMCC heritage advisers and heritage consultants generally recommend:
- Hot lime putty mortar: The most authentic material; requires skilled tradespeople for correct application
- NHL (Natural Hydraulic Lime) mortar: A more practical alternative with better workability; widely accepted in heritage conservation applications
- Tinted Portland cement mortar: A last resort where lime mortar is impractical; colour must be carefully matched to the surrounding stone
The heritage impact statement requirement
All retaining wall development applications in BMCC heritage conservation areas must be accompanied by a heritage impact statement (HIS). The HIS must:
- Describe the heritage significance of the conservation area and, where relevant, the specific property
- Assess the impact of the proposed wall on the heritage character, fabric and setting
- Justify the proposed materials and construction approach as sympathetic to the heritage character
- Identify any historic retaining walls or features to be retained or demolished
- Propose a statement of conservation intent for any heritage fabric affected
A heritage impact statement is prepared by an accredited heritage consultant, typically a heritage architect or historian with NSW Heritage Register accreditation. Cost is $1,500 to $4,000 depending on the property’s significance and the complexity of the proposal.
Working with salvaged sandstone
Salvaged sandstone from demolished buildings or walls has a particular advantage in heritage work: the stone has already weathered to a colour and surface texture consistent with the existing heritage fabric. Colour-matching salvaged stone to existing walls on the same property or in the same street can satisfy heritage consultants and BMCC officers much more readily than freshly quarried stone, which takes years to weather to the same character.
Salvaged sandstone is available through local demolition contractors and architectural salvage dealers. Quality varies, inspect for cracks, structural weakness and contamination before purchasing.
FAQs
Can I use textured or coloured concrete sleepers to mimic stone in a heritage area?
Generally no. Textured or pigmented concrete sleepers have become more visually sophisticated, but BMCC heritage officers typically still require natural stone for heritage-sensitive applications. The key test is not just colour and texture but also the material’s longevity, jointing character and relationship to the surrounding heritage fabric.
My property is not in an HCA but it’s individually heritage listed. Does this affect my retaining wall?
Yes. Individual heritage listings apply the same material and character requirements as HCAs, and in some cases impose even stricter controls on the curtilage (setting) of the heritage item. Your 149 Certificate will identify any heritage listing.
How do I find out if my property is in a BMCC heritage conservation area?
Check your Section 10.7 Planning Certificate (also called a Section 149 Certificate), which is attached to your Certificate of Title, or use BMCC’s BMaps online tool to overlay heritage conservation area boundaries on your property address.
What if my wall is in disrepair, can I just remove it without consent?
Demolishing an existing retaining wall in a heritage conservation area may itself require consent if the wall contributes to the heritage character of the area or property. Before removing any heritage-era retaining wall, check with BMCC whether a demolition permit is required.