Yes, urban planer boxes can be successfully used on a flat roof with a waterproof membrane, but it requires careful planning and specific precautions to protect the roof's integrity. The primary concern is preventing damage to the waterproofing layer, which is the roof's most critical component.
Before installation, a structural assessment is essential to ensure the roof can support the added weight of planters, soil (especially when wet), plants, and people. Always consult with a structural engineer.
To protect the membrane, use these key strategies:
1. Place a protective layer, like a root barrier or a geo-textile fabric, between the planter bottom and the membrane. This prevents abrasion and punctures from the planter itself.
2. Ensure your planter boxes have adequate drainage holes. They should never sit directly on the membrane and block water flow. Use pot feet or a similar support to elevate them, creating an air gap that allows water to drain freely towards the roof's drains or scuppers.
3. Select lightweight planting mediums and consider the mature size of plants to manage weight and root spread. Avoid invasive species with aggressive roots.
By implementing these measures—focusing on weight limits, a protective layer, and proper drainage—you can create a beautiful and sustainable green space on your flat roof without compromising its waterproofing system.