How much space must there be between the existing and new dwelling?
The required separation depends on the residential zone, building height, and whether walls, windows or other unscreened elements face each other.
RZ1 & RZ2
| What faces each other? | Minimum separation |
|---|---|
| External wall ↔ External wall | 3 m |
| Non-habitable unscreened element ↔ External wall | 3 m |
| Non-habitable ↔ Non-habitable unscreened elements | 6 m |
| Habitable ↔ Non-habitable unscreened elements | 9 m |
| Habitable unscreened element ↔ External wall | 9 m |
| Habitable ↔ Habitable unscreened elements | 12 m |
| Unscreened element ↔ Centre of another dwelling's minimum PPOS | 12 m |
RZ3, RZ4 & RZ5
| Building height | Wall ↔ Wall / Unscreened element | Unscreened ↔ Unscreened |
|---|---|---|
| Up to 4 storeys | 3 m | 6 m |
| 5–8 storeys | 4.5 m | 9 m |
| 9+ storeys | 6 m | 12 m |
A 12 m separation applies between an unscreened element and a primary window, or the centre of another dwelling's minimum principal private open space (PPOS).
Important: These are building-separation requirements. Boundary setbacks, privacy, solar access, building height and other planning requirements must also be considered. The exact separation required will depend on the design of the existing and proposed dwellings.
Reference: Planning (Residential Zones) Technical Specifications 2026 (NI2026-303), Assessment Outcome 29.1- Planning (Residential Zones) Technical Specifications 2026
Short Answer
The required separation depends on the zoning and the design of the dwellings. In RZ1 and RZ2, separation generally ranges from 3 to 12 metres, depending on whether external walls, habitable-room windows or other unscreened elements face each other.
In RZ3, RZ4 and RZ5, separation generally ranges from 3 to 12 metres, depending on the building height and the elements facing each other.
The exact separation will be determined during the design process, taking into account privacy, window locations, private open space and other applicable planning requirements.
Detailed Explanation
Where an existing dwelling is retained and a new dwelling is added, the development comprises two dwellings and is therefore assessed against the applicable multi-unit housing requirements. The required separation depends on the residential zone and what parts of the dwellings face each other.
For developments in RZ1 and RZ2, the required separation ranges from 3 metres to 12 metres:
- 3 metres – between an external wall and another external wall.
- 3 metres – between an unscreened element of a non-habitable room and an external wall.
- 6 metres – between unscreened elements of two non-habitable rooms.
- 9 metres – between an unscreened element of a habitable room and an unscreened element of a non-habitable room.
- 9 metres – between an unscreened element of a habitable room and an external wall.
- 12 metres – between unscreened elements of two habitable rooms.
- 12 metres – between an unscreened element and the centre of another dwelling's minimum principal private open space (PPOS).
In simple terms, 3 metres is the minimum building separation in the least privacy-sensitive situation, such as two external walls facing each other. Greater separation is required where windows or other unscreened elements create potential privacy impacts.
For developments in RZ3, RZ4 and RZ5, separation is based primarily on the height of the buildings and what elements face each other:
- Buildings up to 4 storeys: generally 3 metres between an external wall and another external wall or unscreened element, and 6 metres between unscreened elements.
- Buildings 5–8 storeys: generally 4.5 metres between an external wall and another external wall or unscreened element, and 9 metres between unscreened elements.
- Buildings 9 storeys or more: generally 6 metres between an external wall and another external wall or unscreened element, and 12 metres between unscreened elements.
- A separation of 12 metres applies between an unscreened element and a primary window, or between an unscreened element and the centre of another dwelling's minimum PPOS, regardless of the above building-height categories.
What does this mean for your property?
There is no single separation distance that applies to every project. For a typical existing dwelling with a proposed new dwelling, the required distance will depend on the zone, building height, room types, location of windows and openings, and the relationship between the dwellings' private open spaces.
These are also building-separation requirements, not boundary setbacks. The proposed dwelling must separately satisfy the applicable front, side and rear boundary setbacks, as well as other requirements relating to building height, solar access, private open space and the building envelope.
The exact separation can therefore only be confirmed once the existing dwelling and proposed new dwelling have been assessed as part of the site and design process.
No minimum block size does not remove the need for planning assessment.
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