When designing Specialist Disability Accommodation (SDA), many developers and investors instinctively reach for the SDA Pricing Calculator. It is easy to see why: the tool produces a clear, numerical figure of what appears to be the "highest and best use" configuration.
A 1 bedroom apartment with an Onsite Overnight Assistance (OOA) room looks strong.
A row of 1 bedroom villas along a suburban street also looks appealing.
But SDA is not a spreadsheet exercise, and those calculator outputs, while useful, can be misleading when used in isolation.
The reality is that the viability of an SDA home is shaped just as much by the Supported Independent Living (SIL) provider and their roster of care (ROC) as it is by the design category or rental yield in a feasibility model.
Ignore the ROC and your SDA design may be compliant, high yield on paper, and still impossible to staff or lease effectively.
What is a Roster of Care?
A roster of care (ROC) is the structured staffing plan used by a SIL provider to support participants living in an SDA home. It outlines:
- Staffing requirements
- Shift patterns
- Allocation of duties
- Coverage across multiple tenants
- Behavioural considerations and safety needs
For a ROC to be viable, the dwelling must have enough collective SIL funding across all participants to pay for the required staff. The floor plan must also allow efficient staff movement, effective supervision, privacy, safety and independence.
If a dwelling only has one participant with modest funding, the ROC becomes difficult or impossible to deliver. In this scenario the SIL provider cannot safely or economically staff the home, regardless of how attractive the SDA rent appears on paper.
The SDA Calculator Shows Only a Fraction of the Picture
The SDA Calculator assesses a narrow set of design inputs:
- Location
- Design type (house, apartment, villa)
- Carer's room (OOA)
- Fire sprinklers
From these factors (and a few others relating to tax), it produces a rental figure. But the calculator assumes a world where staffing, support delivery, and participant funding do not exist.
The calculator will tell you that a 1 bedroom apartment with OOA has the highest return, and on a per sqm basis, everyone should be building rowhouses of 3 bedroom villas!
None of this reflects whether a SIL provider can staff the home, whether participant funding can support the roster of care, or whether the layout is practical for real-world disability support.
A high-yield design is irrelevant if it cannot be staffed or filled.
The Missing Piece: The SIL Provider and the Roster of Care
Many new SDA investors overlook a fundamental truth: SDA rent only flows if a SIL provider can afford to operate the home.
Participants have two funding streams:
- SDA payments
- SIL funding for care and support
The SDA Calculator only accounts for the first, while daily operations depend entirely on the second.
SIL providers draw on participants' plans to cover support workers, overnight supervision, medication management, behavioural supports, transport and community access.
In a single 1 bedroom dwelling, the sole participant must have an unusually high support package for the provider to cover the full cost of staffing. This is uncommon and creates real financial risk.
One participant means one funding source. One funding source means limited staffing flexibility. Limited staffing flexibility means real operational difficulty.
This is why many single participant designs struggle in practice even though they appear highly profitable in the calculator.
Why Multi Participant Models Often Work Better
If a home can support two or three participants, either within one dwelling or across two neighbouring dwellings, the roster of care becomes significantly more viable.
Funding can be shared indirectly through collective staffing. Examples include:
- One overnight worker supporting multiple participants
- Shared day staff across dwellings
- Reduced labour costs due to efficient supervision
- Greater flexibility in participant compatibility and cohort building
A strong ROC leads to:
- Lower provider costs
- More sustainable service delivery
- Higher tenanting flexibility
- Faster and more stable occupancy
- Reduced vacancy risk
- A stronger long-term investment position
Homes designed with the roster of care in mind almost always outperform homes designed solely to maximise a theoretical SDA rent.
The Most Overlooked Success Factor in SDA
The link between design and care delivery is the element most commonly underestimated by new SDA developers.
It is important to remember:
- A good design is not necessarily a good ROC.
- A good ROC is what makes the home financially viable.
- A financially viable home is what makes the investment strong and resilient.
When developers collaborate with SIL providers early, before locking in a floor plan, they gain crucial insights into:
- How staff operate within the home
- What floorplate elements support or undermine safety
- Participant profiles and compatibility patterns in the local area
- Behavioural support needs
- Practical design considerations that improve safety and functionality
- How to align staffing models with participant funding
Homes designed through this service-led lens lease faster, operate more smoothly and remain tenanted for longer periods.
The Core Message: Build for People, Not for the Calculator
In SDA, the spreadsheet is a guide, not a strategy.
The homes that perform best are those that:
- Support a viable roster of care
- Are practical and safe for participants
- Offer staffing flexibility
- Are economically sustainable for SIL providers
- Attract long-term, compatible residents
- Maintain low vacancy and stable income
You cannot spreadsheet your way to a high-performing SDA investment. You achieve it by designing for people, understanding support models and working hand-in-hand with the providers who deliver the care.