How to Choose the Right Block for a Granny Flat

Does the block qualify for the streamlined approval pathway?

Since the introduction of the NSW Affordable Housing SEPP in 2009, property owners have been able to obtain granny flat approval through a private certifier — bypassing the council — provided the lot satisfies all Complying Development Certificate (CDC) criteria. This is generally the fastest and most economical route to getting a granny flat approved. More detail on the full approvals process is available on our Approvals page.

CDC Site-Requirement Thresholds:

Additional CDC conditions worth checking:

The minimum lot area is 450 m². If a granny flat already exists on the property and you want to build a new one, the existing structure must be demolished first — only one secondary dwelling is permitted per lot.

A primary dwelling (the main house) must already be built on, or formally approved for, the block.

On battle-axe lots, the access handle must be no narrower than 3 m.

What if the block does not fully meet the CDC criteria?

CDC conditions are applied consistently across all of NSW — a property either satisfies every threshold or it does not. If one or more criteria are not met, approval may still be achievable by lodging a Development Application (DA) with the relevant local council. Unlike the uniform CDC rules, DA requirements are set individually by each council through their own Development Control Plans (DCPs) and can vary significantly from one local government area to the next.

Some councils impose additional restrictions that do not appear in the CDC framework. For example, certain councils only permit charged stormwater lines for secondary dwellings, which means a granny flat may not be approved if the block falls away from the street at an angle that would require an absorption pit.

Even if you intend to pursue a DA rather than a CDC, the complying development thresholds remain a useful reference point — many council DCPs mirror these numbers closely, so they give a reliable indication of how much space a granny flat will need on the lot.

Are there any easements or covenants registered against the land?

A Title Search (also called a Certificate of Title) identifies the legal owner or owners of the property and discloses any registered interests that could restrict what you are allowed to build.

Easements grant a third party a right to access or use a defined portion of your land. The most common types are right-of-carriageway easements and stormwater drainage easements. Building over an easement without the proper approvals is not permitted under law.

Covenants are binding obligations attached to the title that regulate how the property may be used or developed. They can dictate the materials and colours permitted on external facades, restrict certain types of structures, or require the maintenance of drainage systems. If a covenant exists on a property you are purchasing, it may be possible to have it removed — either with the written consent of the benefiting party or through an application to the Land and Environment Court (the relevant tribunal in NSW).

Title information in New South Wales is maintained by NSW Land Registry Services. A copy of the title is normally included in the Contract of Sale. If you cannot locate it, a duplicate can be ordered through an online conveyancing search provider.

Does a Sydney Water main run through the lot?

A Sewer Diagram indicates the location of both private drainage lines and any Sydney Water mains within the property boundaries. This document is typically included in the Contract of Sale.

When constructing a granny flat, plumbing is usually connected to the property’s existing private drainage — the simplest and most affordable approach. Main sewer lines located outside the property boundary are not a concern. However, if a main passes through the lot itself, its position may dictate where the granny flat can be placed and introduce additional costs.

Every main sewer line carries a “zone of influence” — a buffer area calculated from the pipe’s depth. If the proposed building location falls within that zone, two options are available:

Option A — Design around the zone of influence. Depending on the buffer width, the position of the pipe and the remaining usable area on the block, it may be possible to reposition the granny flat so that it sits entirely outside the restricted zone. This is almost always the cheaper path.

Option B — Build within the zone of influence. Because Sydney Water owns and protects the pipe, any construction within the buffer requires a sewer encasement — the main is enclosed in concrete for the full length of the building that overlaps the zone, plus one additional metre on each side. For instance, if the granny flat encroaches on the zone for 6 m, a total of 8 m of sewer encasement would be required.

A main sewer running through the proposed build area does not mean the project is unviable. Our designers are experienced at producing efficient floor plans that minimise overlap with the zone of influence and keep encasement costs to a practical level.