For those looking for a property specifically to build a granny flat on, the following checks should be made:

Zoning

Check The 149 Certificate to ensure the property is not in a Bush Fire Zone (BAL 40 +), Heritage listed or a Flood Zone.  It is still possible to apply to build a granny flat through the DA process however a Complying Development is not possible if your property is in one of these zones.

Sewer

Purchase a Sydney Water Sewer Diagram to find out where the sewer is.  The best sites have the sewer located downhill from the building site.   An uphill sewer is acceptable as the waste can be pumped to the sewer.  If a sewer line runs near or under the proposed granny flat site, further investigation will be required.  The sewer may need to be encased in concrete to protect it which may add additional costs to your build. You can pick up a Sewer diagram for the property from a local Sydney Water agent or click here.

Boundaries & Drainage

Purchase a copy of the Deposited Plan which shows where the boundaries are, land size and drainage easements if applicable.  These plans can be bought on-line for $13.55 from the Land and Property Information website

Trees

Are there Protected Native trees on or near the property?  Your local Council will have a list of protected trees.   Your granny flat cannot be built within 3m of a significant tree.  You may be able to apply to the Council to have the tree removed.

Drainage

Check the plans to determine where the stormwater drains are located.  If necessary stormwater can be disposed of onsite using a dispersion pit.  This requires some additional yard space.