Load data for roof garden design

Rooftop Garden Design: Planting Area

1. The weight of different plant types varies significantly. For example, grass turf is around 5 kg/m², small shrubs are about 10 kg/m², large shrubs range from 20–30 kg/m², trees up to 10 meters tall can weigh 60 kg/m², and larger trees (up to 15 meters) may reach 150 kg/m².

2. Artificial planting soil is typically a lightweight synthetic mix with a density between 700–1600 kg/m³. When calculating, it's important to consider the wet density after watering, which can increase by 20% to 50%, depending on moisture content.

3. Drainage layers, such as gravel, vermiculite, or coarse sand, have a much higher density, ranging from 2000–2500 kg/m³. Lightweight materials like ceramsite, on the other hand, only weigh around 600 kg/m³.

Rooftop Garden Design: Water Features

Water bodies add significant weight. For instance, a 30 mm deep water layer contributes 300 kg/m², while a 50 mm depth adds 500 kg/m². The walls of the water feature should be calculated based on the material used, and the height of the pool must be converted into a load per square meter for accurate structural planning.

Rooftop Garden Design: Rockery

Rock structures or rockeries require careful calculation. The actual volume of the rockery is multiplied by a porosity factor of 0.8–0.9, depending on the stone type, and then distributed as a load per square meter.

Rooftop Garden Design: Additional Structures

Any additional structures, such as pergolas, benches, or walkways, must also be considered in the load calculation. These are usually supported by columns or beams, so the weight is concentrated in specific areas. It’s crucial to convert these loads into equivalent uniform loads over the supporting area to ensure the structure can handle the added weight safely.