SDA Design Categories Explained: What Investors Need to Know

Every SDA dwelling in Australia falls into one of four design categories. The category determines the accessibility features the dwelling must include, the types of participants it can house, and the NDIS funding rate it attracts. For investors, the design category is one of the most consequential decisions in an SDA project.

The SDA Design Standard

The NDIS SDA Design Standard was published in October 2019 and took effect on 1 July 2021. It defines four design categories across 25 individual design elements. Every new SDA dwelling enrolled after that date must be certified against one of these categories by an independent third-party assessor.

If you are new to SDA entirely, start with our guide on what SDA is and who qualifies. This article assumes you understand the basics and focuses on what the four categories actually require.

1. Improved Liveability

Improved Liveability dwellings provide reasonable physical access combined with enhanced provisions for people whose primary barriers are not physical but sensory, intellectual, or cognitive. The focus is on making the environment easier to understand and use.

Key features include:

• Luminance contrasts between surfaces, walls, and fittings
• Improved wayfinding through layout and visual cues
• Reduced spatial complexity
• Enhanced lighting throughout the dwelling
• Acoustic considerations to minimise sensory overload

Improved Liveability attracts the lowest SDA funding rate of the four categories, reflecting the lower build cost relative to the more physically complex categories.

2. Fully Accessible

Fully Accessible dwellings offer a high level of physical access for people with significant physical impairment. These are homes where a person using a manual or powered wheelchair can move freely through every space.

Key features include:

• Comprehensive wheelchair access throughout
• Wider doorways and corridors
• Accessible bathrooms and kitchens
• Step-free, level entries to the dwelling

Fully Accessible sits in the middle of the funding spectrum. It requires more specialised construction than Improved Liveability but less than the top two categories.

3. Robust

Robust housing is built to withstand significant wear. These dwellings combine high physical access with materials and fittings designed to reduce reactive maintenance and minimise safety risks. The goal is a home that stays safe and functional even under demanding conditions.

Key features include:

• Secure windows and doors
• High-impact wall lining
• Resilient fittings and fixtures
• Soundproofing between rooms and dwellings
• Laminated glass
• Durable finishes across all surfaces

The Robust category has seen the fastest growth of any design category in recent years. Over the two years to March 2025, Robust dwellings grew by 63%, with 549 new dwellings added to the enrolled stock. That growth reflects increasing recognition of unmet demand for housing suited to people with complex behaviours.

4. High Physical Support (HPS)

High Physical Support is the most complex and highest-funded SDA design category. An HPS dwelling includes every requirement of the Fully Accessible category, plus additional features that support people who need substantial daily physical assistance.

Additional features beyond Fully Accessible:

• Kitchen appliances accessible from both seated and standing positions
• Structural support for ceiling hoists (in bedrooms and bathrooms)
• Provisions for assistive technology integration
• Emergency power supply (backup generator or battery)

HPS receives the highest NDIS SDA price limits, reflecting the significantly higher build cost and specialist features required. Over the two years to March 2025, HPS saw 49% growth with 1,645 new dwellings enrolled — the largest absolute increase of any category.

How design categories affect investment returns

The design category is not just a technical specification. It directly shapes the financial profile of an SDA investment. NDIS pricing varies significantly between categories, and so do construction costs, participant demand, and vacancy risk.

HPS dwellings attract the highest payments but cost more to build and require more specialist design input. Robust dwellings have their own cost profile driven by durable materials and soundproofing. Improved Liveability is cheaper to construct but attracts lower NDIS payments.

The right choice depends on the local demand profile — which design categories are undersupplied in that region, and what type of participants are waiting for housing. Building an HPS dwelling in a region where demand is concentrated in Robust will not solve the problem for participants, and it will not fill your vacancy.

For a detailed look at what can go wrong, see our guide to SDA investment risks. For the step-by-step process of getting a dwelling designed, built, and enrolled, read the SDA development process.

How dwellings are certified

Every SDA dwelling must be assessed and certified by an accredited third-party SDA assessor. The assessor must be independent from the developer, the builder, and the SDA provider. They cannot certify a project they designed, built, or surveyed themselves. This independence requirement exists to prevent conflicts of interest and ensure the dwelling genuinely meets the standard.

A dwelling is certified for a single primary design category. While higher categories incorporate the requirements of lower ones (HPS includes everything in Fully Accessible, for instance), the dwelling is enrolled under one category for pricing purposes.

Frequently asked questions