Rooftop sustainable urban drainage solutions (SuDS)
The development and expansion of towns and cities has seen exponential use of impervious surfaces causing artificially high rates of rainwater runoff. In measures to prevent flooding, planners are restricting the amount of rainwater leaving a site via the drainage system which can be limited to 5-10 litres per second per hectare, the same flow rates for regional greenfield sites.
What is a blue roof?
A BauderBLUE roof controls rainwater where it lands, one of the core pillars of SuDS design. The blue roof outlet restricts the discharge of stormwater to a calculated and defined flow rate to significantly slow down the volume of water leaving the site. As the storm passes, water continues to discharge from the roof at a controlled rate over a set period (typically up to 48 hrs).
This rooftop SuDS design has weight load implications and the project’s structural engineer will need to be engaged at an early stage.
There are different options available to the construction designer to achieve a blue roof depending on the finish desired and the volume of water to be attenuated.
When to specify...
A BauderBLUE roof system can be constructed at either rooftop or podium level with a variety of landscape finishes including green roofs, biosolar PV array, or hard landscaping.
Usually required to meet planning when restrictions have been placed on the construction to limit the flow rate of rainwater leaving a site via the drainage system.
Outline of our BauderBLUE solutions
- Three different systems with stormwater flow restrictor outlets.
- Our specification service will confirm suitability of waterproofing system for each roof area.
- Warm, uninsulated and inverted roof design options.
- Single point guarantee to comply with client's insurance company requirement.
Achieving technical objectives
- Detailed, project specific discharge rates to match drainage requirements forthe site.
- Precise volume and weight of water held with overflow to ensure the maximum water level (H-max) is never exceeded.
- Design support to meet relevant British Standards and blue roof guidane criteria.
Contact us today about your project
Each project is unique in its requirements, but we have case studies and examples of our work available to help guide you. If you are looking for a particularroof system, then get in touch with our team to discuss your project’s individual needs.
Discuss your Flat Roof Project
| Categories | STORMsub | STORMcell | STORMvoid |
| Controlled discharge flow rate | X | X | X |
| Inbuild overflow | X | X | X |
| Paving finish | X | X | |
| Green roof finish | X | X | |
| Multiple surface finishes | X | ||
| Low-cost option | X | ||
| High volumes of water storage | X | X | |
| Suitable for inverted blue roofs | X | X | |
| Highest ecological value | X | ||
| Non-combustible build-up | X | ||
| High compressive strength | X | ||
| Low profile blue roof | X | X |
Waterproofing a blue roof
It is critical to ensure the waterproofing system is able to meet the demands placed on it by the blue roof. Additionally, the design should minimise the risk of water ingress by eliminating penetrations within the blue roof areas.
- Reinforced Bitumen Membrane Systems
TheBauder Total Roof System (BTRS) and Bauder Total Roof System Plus (BTRS PLUS) are suitable for a blue roof and both incorporate modified bitumen membranes and a range of insulations. Either system can be specified as a warm or inverted roof construction. See our Reinforced Bitumen Membrane brochure for full details on these systems.
- Hot Melt Structural Waterproofing System
Hot Melt Structural Waterproofing System is a seamless monolithic liquid waterproofing that is hot applied to the deck. This type of waterproofing is popular for podium decks. The durability of this system matches the expected service life of the structure, as stated in BBA certificate 06/4350. Specified as a cold or inverted roof construction. See our Hot Melt Structural Waterproofing brochure for further information
- Incorporating a Green Roof
For either, BTRS, BTRS PLUS, or Hot Melt, a root resistant membrane is specified to prevent plant roots and rhizomes damaging the waterproofing.
- Roof penetrations
The blue roof design must minimise or eliminate penetrations in the area where water is to be attenuated, other than the rainwater outlets or emergency overflows that are required for drainage functionality. In a fewinstances, it is possible to individually isolate the roofpenetration. This is achieved by forming a secondary sealbetween the vapour control layer and the underlay or theunderside of the waterproofing, set 250mm back from the penetrations.
