CDC or DA: which granny flat approval do you actually need in NSW?

CDC and DA are the 2 approval pathways for a granny flat in NSW. CDC is a tick-the-boxes approval issued by a private certifier: if your block meets every standard, it cannot be refused. DA is a merit assessment by your council, used when your block does not meet those standards. CDC is faster and cheaper. DA is the fallback, not a failure.

Which one applies to you is not a choice. It is determined by your block.

Both pathways sit under the State Environmental Planning Policy (Housing) 2021. The complying development standards for secondary dwellings are in Schedule 1 of that policy.

The logic is simple. Meet every standard in Schedule 1, and you qualify for CDC. Miss any one of them, and you go to DA.

There is no partial credit and no negotiating with a certifier. A certifier has no discretion, which is exactly why CDC is fast. A council does have discretion, which is why DA takes longer but can approve things CDC never could.

BlueGum’s published timeframes are 4 to 6 weeks for CDC and 3 to 6 months for DA. Those are indicative. Council workload, requests for further information, and site complexity all move them.

This is the part most guides get wrong. Nearly every article you will read states NSW setbacks as flat numbers, usually “900mm to the side and 3m to the rear”. Those figures are only correct for one band of lot sizes. The standards are tiered by how big your lot is.

Here is what Schedule 1 actually says.

• Minimum lot area of 450 m² (section 54(2)(c))
• Land in a residential zone. Zone R5 Large Lot Residential is excluded from CDC, even though a granny flat is permitted there with consent (section 54(1)(a))
• Only one principal dwelling and one secondary dwelling on the lot when finished
• The lot cannot later be subdivided (section 51)
• On a battle-axe lot, the access laneway is excluded when working out the lot area

Capped at 60 m², unless another planning instrument covering your land allows more (section 52(2)(c)). This is a hard ceiling on both pathways, not just CDC.

Maximum 8.5 m above existing ground level for the granny flat itself. Detached outbuildings are capped at 4.8 m and fences at 1.8 m.

Then add 25% of any building height above 3.8 m. A 5 m tall granny flat on a 600 m² block needs 0.9 m plus 25% of 1.2 m, so 1.2 m in total.

The height loading catches people out. On a 600 m² block, going from 3.8 m to 4.8 m tall pushes the rear setback from 3 m to 6 m, which can cost you the whole building envelope.

Normally the average of the 2 nearest dwelling houses on the same side of the street within 40 m. If there are not 2 within 40 m, it falls back to 4.5 m for lots between 450 m² and 900 m², 6.5 m up to 1,500 m², and 10 m above that. Classified roads require 9 m.

At least half of that landscaped area has to sit behind the building line.

• Basements
• A roof terrace on the topmost roof
• Land the Codes SEPP excludes, which includes certain environmentally sensitive land and heritage items

Bush fire prone land, flood control lots and land near the Siding Spring Observatory have their own additional standards in sections 57 to 59.

You go to DA. That is not a dead end, and it is worth being clear about why.

A DA is assessed on merit, which means council weighs the proposal against its own planning controls and can approve something that does not fit the CDC checklist. Plenty of granny flats that fail CDC by a small margin get approved through DA without much drama.

Common reasons a Sydney block ends up on the DA path:

• Lot slightly under 450 m², which is very common in the inner and middle ring
• Frontage under the tier threshold, particularly on older subdivided blocks
• Heritage listing or a heritage conservation area
• Flood affected land
• Bush fire prone land above the lower BAL ratings
• An existing structure or tree that cannot be moved
• Zone R5

DA costs more and takes longer. It is still an approval.

You will see CDC timeframes quoted as 10 to 20 business days. That figure comes from certifier practice, not from the legislation, and it assumes a complete application with nothing outstanding. The clock in practice starts when your documents are actually finished, not when you first ring a builder.

Realistically, the drawings, survey, soil test and BASIX certificate take longer than the certifier does.