Drainage and water retention are related but different functions within a green roof. water retention drainage boards should be selected to provide the specified balance of stored water and discharge. The useful question is how the product fits the roof build-up and planting requirements, not simply whether its cavities appear deep.

Another proposal may use roof garden drainage mats within a different drainage arrangement. Compare each complete layer sequence, including filters and accessible outlets. This article explains the purchasing questions that prevent retention volume from being mistaken for drainage capacity.

State the planting objective

Identify vegetation, growing medium and irrigation strategy for landscape review. The drainage or reservoir layer is one component of that plan. Avoid promising a plant outcome from a board's cavity volume alone. The planting specialist should assess the proposed balance alongside climate, maintenance and the other layers.

Separate storage and flow figures

Request the definitions and conditions behind stated water-retention and drainage values. Record the installed orientation and product model. A stored-water figure does not explain how excess water exits. Keep the two functions on separate lines in the comparison so a larger reservoir is not automatically ranked as a better drainage layer.

Keep outlets serviceable

Show drains and access around them after the planting is complete. Specify how the filter and board connect without closing the discharge path. Water retained by design should be distinguished from water trapped by an incomplete outlet detail. Inspect these transitions before growing media makes them difficult to reach.

Coordinate loads and levels

Include the accepted roof loading information and full layer depth. Changing reservoir capacity or board thickness can affect the build-up and should be reviewed. Do not select a taller board independently of fixed thresholds, media depth and structural requirements. Use the coordinated section as the basis for alternatives.

Issue a balanced enquiry

Send Suneco New Materials the required retention function, drainage requirements and roof section. Ask for exact-model data and connection guidance. The accepted product should support the complete planting and drainage proposal rather than be chosen from a single cavity or flow number.