Special case: Retention on utilized areas

Rainwater retention on utilized areas, e.g. terraces or balconies, is generally not recommended. Instead, retention should be carried out on the roof surfaces. However, if this is unavoidable, increased requirements for planning and execution apply, as the heights of door thresholds and other sealed components are often lower than on unused roof surfaces.

For main drainage with retention, a strong emergency drainage should always be planned.

The following questions/considerations are intended to help the specialist planner or architect assess the particular challenges of official discharge restrictions with retention on utilized areas.

Fundamentals

- How will the area be used later?
- What basic structure and surface covering should the area have?
- Has adequate emergency drainage been considered?

Water levels

- According to DIN 1986-100: 2016-12 Point 5.10 Paragraph 2, flooding on terraces or loggias should be avoided.
- What connection heights of the waterproofing must be considered?
- Is barrier-free use of the balconies desired, with particularly low connection heights?

Stagnant water

- Has attention been drawn to possible odour nuisance from stagnant water?
- Has it been pointed out that greening of the surface structure is promoted by standing water?

Further topics

- Freezing of the utilized area, is the use of heating possibly necessary?
- Is increased reinforcement required due to the increased static load?

Since the topic of retention roof drainage is not yet included in the currently valid standards for drainage, these are fundamentally object-specific solutions.

For further questions, our Mr. Schaper is available at Tel. 05382 - 71 275.