Would I have to knock down my existing house for a multiple-occupancy development?
Keeping the existing house is possible in some multiple-occupancy designs. In fact, the ACT Missing Middle Housing Design Guide specifically illustrates a detached dual-occupancy layout that retains the existing dwelling, showing that demolition is not an automatic requirement.
The question is whether the existing house is in a useful position.
For example, if it sits toward the front or one side of the block and leaves enough usable land, it may be possible to keep the house and add another dwelling behind or alongside it.
If the existing house occupies the middle of the block, however, it may restrict where additional dwellings, vehicle access, parking and private open space can go. The development also needs to work with matters such as setbacks, site coverage and other applicable planning controls. In that situation, knocking down the existing house and designing the whole site as one development may provide a better outcome.
The Missing Middle Design Guide itself notes that the appropriate layout depends on matters including planning controls, solar orientation, slope, adjoining buildings, block dimensions and block shape.
Reference: Planning (Missing Middle Housing) Design Guide 2026 (NI2026-312) – https://www.planning.act.gov.au/__data/assets/pdf_file/0020/3092411/ACT-Missing-Middle-Housing-Design-Guide.pdf
Short Answer
Not necessarily — but for some blocks, demolition may be the most practical way to achieve a full multiple-occupancy development. Whether the existing house can stay depends largely on where it sits on the block and whether the remaining site can accommodate the additional dwellings and all applicable planning requirements.
So the practical answer is: retention may be possible, but if the goal is to maximise the block’s multiple-occupancy potential, demolition may sometimes produce the more workable development layout.
Detailed Explanation
There is no general requirement under the Missing Middle reforms that an existing dwelling must be demolished before multiple-occupancy housing can be developed. The current reforms expressly enable multi-occupancy housing, including dual and tri-occupancy development, in RZ1 and RZ2.
Whether retention is feasible therefore needs to be determined through the site design. The Missing Middle Housing Design Guide is particularly useful here because its typical layouts include an example of detached dual occupancy retaining an existing dwelling, while also cautioning that layouts require further refinement for matters such as access, parking and site coverage.
If retaining the existing house is important, that should therefore be treated as an early design constraint and tested before assuming demolition is necessary.
No minimum block size does not remove the need for planning assessment.
Would you like to know what these rules mean for your property?
Get a Planning Assessment prepared by our experienced planning team.