A well-designed roof works much like a wide-brimmed hat, akin to those worn by rice field farmers. Just as a hat provides shade and directs rain away from the wearer, a good roof protects a home from harsh weather while efficiently shedding rainwater away from the structure. However, the concept doesn’t stop at the roof—good site design follows the same principle, ensuring water is directed safely across the property, preventing flooding, erosion, and foundation issues.
By embracing this principle in both roofing and site planning, homeowners can extend the life of their home, minimize maintenance costs, and make use of valuable rainwater resources.
The Role of Roof Design: Shedding Water Effectively
A Roof’s Primary Functions: More Than Just Shelter
A roof’s role in a house goes beyond providing cover—it directly influences water management, shading, insulation, and even the energy efficiency of a home.
A well-designed roof should:
✔ Keep water out—preventing leaks and structural damage.
✔ Direct water away from the home—reducing erosion, splashback, and foundation damage.
✔ Provide shade and passive cooling—reducing heat gain in summer.
✔ Enable rainwater collection—for sustainable water use.
Key Roof Design Features for Effective Water Shedding
Pitch & Slope: Steeper roofs shed water faster, preventing pooling and reducing long-term maintenance.
Eave Overhangs: Wide eaves (600mm–1200mm or more) help direct rainwater away from walls and protect windows and doors from water damage.
Gutter Systems & Downpipes: Well-designed gutters prevent uncontrolled runoff, directing water safely to drainage or storage.
Roof Material Selection:
Corrugated metal roofing is great for quick water shedding and rainwater harvesting.
Tiled roofs provide durability but require well-placed gutters to handle runoff.
Green roofs absorb water and reduce runoff but need careful structural planning.
Integrated Drainage Points: Avoid placing downpipes where they cause excessive splashback or erosion. Instead, connect them to rainwater storage or garden beds.
Practical Example: A Home Built for Rain Management
A well-designed passive solar home in Canberra might feature a north-facing roof with an extended overhang to provide shade in summer while allowing low winter sun to warm the interior. The roof would slope to direct rain into a water tank, with overflow safely directed into a landscaped rain garden. This ensures efficient water use and prevents damage from uncontrolled runoff.
Extending This Concept to Site Design
A home’s ability to manage water isn’t just about the roof—it must extend into the overall site layout and landscape design. Just as a hat sheds water away from the body, a house must shed water away from its foundations and structures while making use of natural fall and gravity.
1. Preventing Water Accumulation Near the Home
If water is allowed to pool around a house, it can lead to:
❌ Foundation issues from prolonged dampness.
❌ Erosion of surrounding landscaping.
❌ Mould, mildew, and rot on external walls and footings.
To avoid these issues:
✅ Ensure the ground slopes away from the house (typically a 1:50 gradient or greater).
✅ Use gravel drains or swales to guide water away.
✅ Avoid placing paved areas directly against walls without proper drainage.
✅ Install subsurface drainage (such as ag pipes) near footings if necessary.
2. Avoiding Water Shedding onto Neighboring Properties
A poorly designed house can unintentionally flood a neighbor’s yard or street if drainage is not properly considered.
To prevent disputes and compliance issues:
✅ Ensure water runoff remains within your property boundary.
✅ Direct water into on-site drainage systems rather than onto neighboring lots.
✅ Install rainwater detention tanks to slow the release of excess water.
3. Using Natural Slopes to Your Advantage
Instead of fighting against a site’s natural topography, work with it.
On sloping sites, position driveways and paths so that water naturally flows into gardens or retention areas.
Use terracing and retaining walls to slow down and control runoff.
Position rain gardens at low points to catch and filter water before it leaves the site.
Opportunities for Water Capture and Reuse
Rather than seeing runoff as a problem, a well-designed home turns rainwater into a resource.
1. Rainwater Harvesting for Home Use
Roof runoff can be captured into rainwater tanks for garden irrigation, toilet flushing, and even potable use (if properly filtered).
Above-ground or underground tanks can be sized according to rainfall levels and site requirements.
First-flush diverters improve water quality for domestic use.
2. Permeable Surfaces for Reduced Runoff
Instead of letting water run off hard, impermeable surfaces, consider using:
Permeable pavers for driveways and pathways.
Gravel or crushed rock in low-traffic areas.
Vegetated swales to filter and absorb water.
3. Bioswales & Rain Gardens for Passive Irrigation
A bioswale is a landscaped channel that slows water flow and filters pollutants before it enters stormwater systems.
Rain gardens collect runoff in planted areas, allowing it to soak into the soil instead of washing away nutrients.
4. Retention Ponds & Soak Pits
For larger properties, retention ponds can hold excess rainwater, preventing flooding and allowing gradual infiltration into the ground. Soak pits (gravel-filled drainage holes) can be placed in lower sections of the site to manage heavy rainfall events.
Future-Proofing Your Home’s Water Management
With climate change increasing extreme weather events, homes must be designed to handle both heavy rain and drought periods.
✔ Ensure gutters, downpipes, and drainage systems can handle heavy rainfall events.
✔ Plan for future expansion—if you may add extensions, ensure existing drainage can accommodate increased runoff.
✔ Integrate smart water use technologies like greywater recycling and automated irrigation.
Final Thoughts: A Thoughtful Approach to Roof & Site Water Management
By applying the wide-brimmed hat principle, homeowners can create:
✔ More resilient homes that resist water damage.
✔ Low-maintenance designs that don’t require constant repairs.
✔ Sustainable water systems that reduce reliance on mains water.
✔ Harmonious landscapes that work with nature rather than against it.
A well-designed roof doesn’t just shed rain—it works with the site to control and utilize water efficiently. Whether you're designing a new home or retrofitting an existing one, thoughtful roof and landscape planning can make a huge difference in comfort, sustainability, and long-term performance.