Rear and side setbacks for granny flat

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Dear Blacktown City Council,

We are planning to build a house and granny flat by knock down the existing house in Blacktown. May I request following information. I tried to go through the BDCP 2015 however couldn't find answers to my queries (most probably due to lack of my knowledge)

Scenario: 556 sqm lot (15m x 36m). Building a doubnle story at the front and 60 sqm granny flat at the back. There are other properties at back and sides of this block. The block is sloping to back around 1m

1. Granny flat setbacks from side and rear fence
2. POS for house and granny flat
3. Can these 2 dwellings share one rain water tank through charged stormwater pipes and then discharge pipe from rain water tank to street by gravity. There is no compliant space for OSD pit. Assuming that neighbours might not be willing for easement.
4. Minimum driverway gradient required as per council to push the rainwater/stormwater away to street
Thanks in advance.

Yours faithfully,


Blacktown Council, Blacktown City Council

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Lewis Warner, Blacktown City Council

Hi KD,

From what you've described it sounds like the lot in question may not be suitable for a granny flat development. I can give more accurate comments if you provide me with the proposed development address.

In response to your individual queries;

1. Side and rear setbacks are both 900mm under DCP part C
2. Granny flat requires 80sqm of POS, primary dwelling requires 80sqm if less than 4 bed, 100sqm if 4 or more bed.
3. No, if developing a primary and secondary dwelling (granny flat) then all roof and surface water must be gravity fed to either the street or the easement. Charged systems are not accepted for this type of development
4. Driveway requirements are available on the residential vehicle crossing form available at the following link

Kind regards,

Lewis Warner
Building Surveyor
9839 5949

[email address]
PO Box 63 Blacktown NSW 2148

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