Building Extension

Full storey, setback storey or cascading storeys with main and emergency drainage

A building extension or roof topping involves adding one or more additional storeys to an existing building. Typical variants include extensions as a full storey, as a setback storey or as multiple cascading storeys. In building extensions, besides the structural aspects, drainage is particularly important.

1) Building Extension with Full Storey

Full storey with combined main-emergency parapet drainage
Full storey with combined main-emergency parapet drainage

For building extensions with full storeys, main drainage and emergency drainage "only" need to be designed for the one newly created roof area according to current rainfall intensity. If the roof structure of the new full storey is planned as a gravel roof or green roof, the corresponding runoff coefficient is used in the drainage calculation.

Usually, the new full storey is flush with the existing facade, so an external LORO-X parapet drainage is suitable. An internal roof drainage can also be used if the existing flat roof drain can be converted into a pipe penetration.

Drainage Recommendations

2) Building Extension with Setback Storey

Building extension with combined setback storey drainage LORO-X QUATTROFLUX
Building extension with combined setback storey drainage

When extending with a setback storey, part of the previously unused flat roof becomes an accessible roof terrace. Above the other part, a recessed new storey is created with a new roof area.

The rainwater from the (new) roof usually must not be directed onto the lower (new) roof terrace but must be routed in a backflow-proof closed pipe system across the roof terrace.

With the LORO-X QUATTROFLUX setback storey drainage, main and emergency drainage are controlled safely across the roof terrace in one system.

Drainage Recommendations

3) Building Extension with Cascading Storeys

Building extension with cascade drainage LORO-X DUOSTREAM
Building extension with cascade drainage

For larger roof areas, multiple storeys can also be added in cascading construction. This creates a new roof area but also multiple new roof terraces. Each new roof terrace must be drained without directing water onto the respective lower roof terrace.

The LORO-X DUOSTREAM cascade drainage features multi-storey drains for draining the respective roof terrace, which simultaneously guide the water from the upper storeys in a closed system across the roof terrace.

Drainage Recommendations