1. Zoning and permissibility
Dual occupancy is permitted in most low-density residential (R2) and medium-density (R3) zones across Sydney, but the exact rules live in your council's Local Environmental Plan (LEP). Some councils permit dual occupancy widely; others restrict it or set extra conditions. The Section 10.7 planning certificate for your property confirms the zoning and the controls that apply.
2. Lot size and frontage
Two numbers do most of the work: your lot area and your street frontage. Under the Low Rise Housing Diversity Code, a common Complying Development (CDC) benchmark is a minimum 450m² lot with a 12m frontage. Many councils set their own minimums in the LEP for a Development Application (DA). If you're under these numbers, a duplex may still be possible via DA, but it's the first thing to check.
3. Approval pathway, CDC or DA
If your site meets every standard, a CDC can approve the duplex in as little as around 20 days. If it doesn't, because of an overlay, a shortfall, or design merit, a DA assessed by council is the path. Knowing which pathway fits shapes the entire design.
4. Overlays and constraints
Flood, bushfire (BAL), heritage, easements, significant trees and foreshore controls can all change what's possible, and often move a project from CDC to DA. A quick overlay check early saves expensive surprises later.
5. Your subdivision goal
If you want to sell or hold two separate titles, subdivision (Torrens or strata) has to be planned from the first sketch, it isn't automatic just because you build two dwellings. Deciding this early affects the design, the party wall and the approval strategy.
Frequently asked questions
Send us your address. We check zoning, lot size, frontage and overlays against the current controls and give you a preliminary read, usually the same conversation.
Authoritative sources: NSW Planning Portal, NSW Low Rise Housing Diversity Code.