Blue Roof Frequently Asked Questions

What happens if a Blue Roof becomes blocked?

Blue Roof maintenance requirements are stipulated to prevent the occurrence of a blockage. Each roof is designed to ensure that no overflow occurs for the prescribed design storm event. However, as a further precautionary measure, one Harmer weir overflow outlet is typically specified for each Harmer BluRoof outlet.

In the event of a storm that exceeds the design storm parameters, the overflow outlets will discharge stormwater in the same manner as a conventional flat roof (i.e. instantaneously). As such, overflows are designed to discharge stormwater that exceeds the Blue Roof storage capacity in accordance with BS EN 12056-3:2000.

How does a Blue Roof impact on the structural capacity of the roof structure it is installed on?

The loads imposed by a blue roof will be checked against the capacity of the roof’s structure by the appointed structural engineer on a project by project basis in accordance with the calculated volume of water attenuated.

How long does the water take to drain from the Blue Roof?

This will be determined by the number of Blue Roof outlets specified, and any key design targets that have been stipulated, i.e. volume of water attenuated, or % reduction in the peak run-off rate.

Taking those targets into account, the roof area will however by designed so that the system entirely discharges of water within 48 hours, in accordance with good SuDS practice.

Can a roof be installed to zero falls?

Installing a roof at zero falls, a key design factor that allows cost and weight savings to be made by omitting the need for a screed to falls, is achievable when specifying Hydrotech 6125 Structural Waterproofing. The monolithic nature and high bond strength of the Hydrotech waterproofing allows for the system to be installed in this manner, which is reinforced by third party accreditation in the Hydrotech BBA certificate 90-2431.

This advantage, coupled with the unrivalled track record of no product failures in over 50 years of installation, makes Hydrotech 6125 the optimum choice for large roof areas, podiums and courtyards, particularly in buried, hard and soft landscaped build-ups.

If you would like to find out more about our BluRoof Stormwater Management System click here, to request a brochure click here.

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