Ballast, Roof

Definition

Roof ballast is crushed rock or gravel that is spread on a roof surface to form its final protective and functional layer. This ballast is commonly used on flat or low-slope roofs.

Purpose

The primary purpose of roof ballast is to provide a protective layer that stabilizes the roofing membrane, protects it from UV radiation and physical damage, and helps to hold the roofing materials in place, especially in windy conditions. It also aids in drainage and can improve the roof’s overall thermal performance.

Examples of Use

1. Flat Roofs: On commercial buildings with flat roofs, ballast is spread over the roofing membrane to secure it and protect it from weather elements.
2. Green Roofs: In green roofing systems, ballast can be used to provide initial stability before vegetation is established and to create pathways or borders.
3. Inverted Roofs: In inverted or protected membrane roof systems, ballast is placed above the insulation layer to keep it in place and protect the underlying membrane.
4. Solar Panel Installation: Ballast can be used to secure solar panel mounting systems on flat roofs without penetrating the roof membrane.

Related Terms

• Roof Membrane: A waterproof layer used on roofs to prevent water penetration, often requiring ballast to secure it.
• Flat Roof: A type of roof that is almost level, commonly found in commercial buildings, which often uses ballast to protect and secure the roofing system.
• Green Roof: A roof that is partially or completely covered with vegetation, where ballast may be used to stabilize the growing medium and structure.
• Roof Insulation: Material used to reduce heat transfer through the roof, often used in combination with ballast in certain roofing systems.

Notes

• Material Selection: The type of ballast used (crushed rock or gravel) should be appropriate for the specific roofing system, ensuring it provides adequate protection and stability.
• Weight Considerations: The weight of the ballast must be considered in the structural design of the building to ensure the roof can support it without compromising integrity.
• Maintenance: Regular inspection and maintenance of ballasted roofs are necessary to ensure the ballast remains evenly distributed and effective in its protective role.
• Drainage: Proper drainage must be ensured on ballasted roofs to prevent water accumulation, which can lead to damage and leaks.