Blurring the boundaries between indoor and outdoor spaces is a popular design trend in Australian homes, enhancing natural light, ventilation, and the overall living experience. However, achieving a seamless transition while maintaining waterproofing integrity and accessibility compliance presents a significant challenge.
A major issue in these designs is the requirement for a set down between internal and external floor levels to prevent water ingress. While this step-down approach is a common solution, it can create accessibility barriers. Fortunately, there are alternative design strategies that allow for a flush threshold while ensuring compliance with waterproofing standards and accessibility regulations.
Understanding Waterproofing and Set Down Requirements
The National Construction Code (NCC) and Australian Standard AS 4654.1 & AS 4654.2 – Waterproofing for External Above-Ground Use set out requirements for managing water drainage and protecting internal spaces from water ingress.
Why is a Set Down Typically Required?
Traditionally, a set down (a lower external floor level compared to the internal floor) is used to:
Prevent wind-driven rain or surface water from entering the home.
Allow for an effective waterproofing transition between the internal and external spaces.
Provide a drainage buffer, directing water away from the home.
However, a set down of 50mm or more can create a trip hazard and hinder accessibility, which is a concern under AS 1428.1 – Design for Access and Mobility.
How to Achieve a Flush Indoor-Outdoor Transition Without a Set Down
To maintain waterproofing compliance while eliminating a step-down, several alternative solutions can be implemented:
1. External Linear Drainage Systems
A high-quality drainage system is crucial when eliminating a set down. Options include:
Linear strip drains placed directly at the transition point to collect surface water.
Rebated stormwater grates that sit flush with external paving to prevent water pooling.
Perimeter trench drains directing runoff away from the entry point.
2. Threshold Drainage and Door System Integration
Modern drainage solutions allow for a completely level transition while keeping water out. Some effective methods include:
Rebated door tracks with integrated drainage that prevent water ingress at the doorway.
Flush sills with concealed drains, particularly in bi-fold and sliding door systems.
Magnetically sealing doors, which create an airtight and waterproof barrier when closed.
3. Flooring Material Considerations
Using continuous or similar flooring materials for both indoor and outdoor spaces enhances the seamless effect, but choosing the right materials is key to waterproofing success:
Non-porous tiles or stone with slip resistance to reduce water absorption.
Composite decking or treated timber with proper drainage beneath.
Polished concrete with a slight fall to direct water toward drains.
4. Slope and Gradient Adjustments
Even without a set down, surface gradients help channel water away:
A 1:100 fall away from the house ensures water moves toward drainage points.
Graded outdoor paving with a slight decline minimizes pooling.
Ensuring external areas have a drainage path to stormwater outlets.
5. Overhead Protection to Reduce Rain Exposure
Minimizing direct rain exposure can lower the risk of water ingress:
Extended eaves or awnings to shield openings from rainfall.
Louvred or retractable pergolas that provide flexible weather protection.
Strategic landscaping elements, such as raised planters, to divert water flow.
Meeting Accessibility Requirements
A flush indoor-outdoor transition is essential for accessibility, particularly for those with mobility impairments. AS 1428.1 requires that door thresholds:
Have no more than a 5mm lip for wheelchair and pram access.
Avoid abrupt level changes that create trip hazards.
Use slip-resistant and stable surfaces to prevent falls.
By integrating threshold drainage systems, proper grading, and weather protection, homes can meet both waterproofing standards and accessibility requirements without compromising on design aesthetics.
Conclusion
A seamless indoor-outdoor transition enhances the flow and functionality of a home, but achieving it requires careful planning to balance waterproofing integrity and accessibility compliance. While a set down is a conventional solution, modern drainage systems, graded flooring, door integration, and weather protection offer effective alternatives that maintain both safety and aesthetics.
With the right design approach, homeowners can enjoy an effortlessly connected indoor-outdoor space that is functional, beautiful, and built to last
