The LiveRoof Integrated RoofBlue® Riser is engineered to provide temporary water detention underneath LiveRoof systems.  When used with control flow drains, RoofBlue expands the usefulness of a green roof system as a stormwater management tool:

  • Reduces burden on stormwater systems (may allow for reduced sized drains).
  • Could reduce or eliminate the need for cisterns, underground storage tanks, detention ponds, etc.
  • May reduce stormwater utility charges or qualify for zoning incentives.
  • May allow for overall reduced project cost by combining retention of a green roof and blue roof in a smaller area to meet minimum local stormwater management requirements.

Maximum water detention capacity:
At 3.5”maximum water depth, RoofBlue provides up to 455 cubic inches (approximately 2 gallons or 7.4 litres) of water detention per square foot.

Frequently Asked Questions

What is a blue roof?

A blue roof is designed to slow or store stormwater runoff, easing the burden on the stormwater systems.  When combined with the LiveRoof® brand green roof system—which in itself is an effective stormwater tool—the RoofBlue system maximizes rooftop stormwater management capability.  This may greatly reduce the need for other onsite stormwater management tools, such as cisterns, detention ponds, or underground storage tanks.

What is the difference between rooftop detention and rooftop retention?  And, which is RoofBlue recommended for?

Retention means that a specific volume of water is retained on the roof for an indefinite period of time.  Detention means to temporarily detain stormwater before discharging it as runoff.  RoofBlue is intended for use as part of a water detention system, whose main function is to delay and control the flow of stormwater runoff.  This delay allows more time for municipalities to treat runoff, which helps to prevent stormwater and combined sewage systems from overflowing untreated runoff into local waterways.

How much water can be stored underneath the LiveRoof system using RoofBlue risers?

  • The riser raises the modules an additional 3.5” from the roof surface.  The riser void space is approximately 90.5%.
  • At 3.5”maximum water depth, RoofBlue provides up to 455 cubic inches (approximately 2 gallons or 7.4 litres) of water detention per square foot.
  • The control flow insert height should be set so that at the lowest point of the green roof installation, the water will not exceed 3.5” in height.  This ensures that the plant roots kept out of standing water.

What is a control flow drain?  And, how do I select the right one for my blue roof application?

Control flow drains are designed to meter the rate of runoff from roofs where uncontrolled water flow would burden storm drain systems.  These drains typically have an insert with a weir that regulates the flow of water through the drain.  They are available in a variety of heights.  Generally, flat roofs have lower weir heights than sloped roofs.  Some models have adjustable weirs which can be set for each drain / location.  For added security, consider copper drain flanges and monitored leak detection systems.  All control flow drain systems should be carefully designed by a licensed professional engineer.  These manufacturers sell controlled flow drains:

  • Raintrol® by JR Smith
  • Zurn®
  • Josam Flo-Set®
  • Thaler Metal
  • Accuflow by Mifab
  • Watts Accutrol
  • Lexcor
  • Wade

How much additional load does a blue roof add?

RoofBlue applications should be designed to hold no more than 3.5” of water beneath the green roof system.  Each inch of water weighs approximately 5.2 pounds per square foot, so at maximum water detention, the blue roof solution would add up to 18.2 pounds per square foot of load (in addition to the load of the green roof system).  For the saturated weights of the green roof system, see the LiveRoof System Options page.

What is the maximum amount of time that rainwater may stand on the rooftop?
In our experience, most roofing assemblies recommend that water does not stand for longer than 24 hours.  However, we recommend that architects and engineers confirm the maximum amount of time allowable for detention with the membrane manufacturer before specifying the size and placement of drains and pipes. 

Which LiveRoof System Options are recommended for use with RoofBlue®?
The RoofBlue riser is compatible with all LiveRoof module sizes.  The riser will raise the green roof system by an additional 3.5”, which means that taller aluminum edge restraints are required to surround the entire blue / green roof assembly.   When RoofBlue is used with the LiveRoof Lite (2.5”) system, the 6.5” RoofEdge® should be used, and for the LiveRoof Standard (4.25”) system, the 8.5” RoofEdge should be used.

LiveRoof does not manufacture an edging product taller than 8.5” – to use deeper profiles, use a custom fabricated taller edge restraint.  Alternatively, use one or more rows of LiveRoof Standard (4.25”) vegetated roof modules at the perimeter and transition to the LiveRoof Deep (6”) or Maxx (8”) systems in the field of the installation.  The modules are designed to integrate between these sizes without edging.

What type of waterproofing system should be used on blue roofs?
Most membrane manufacturers will have special requirements for blue roof applications.   In the early stages of blue roof design, is absolutely critical for engineers and specifiers to work with membrane manufacturers to select appropriate materials, thicknesses and to provide assembly instructions according to local code.

Also, confirm that the waterproofing specification complies with code.  Some municipalities have specific requirements for blue roof applications.  For example, New York City has required a secondary, redundant waterproofing membrane for rooftop water detention.