Alumasc’s BluRoof – frequently asked questions

Posted by Ashlea Williamson

Q1. Can we purchase an Alumasc Blue Roof outlet without the waterproofing?

Blue Roof build upAlumasc has developed the BluRoof system that benefits from the combined expertise associated with Harmer Engineered Drainage Systems and Alumasc Roofing Systems. The result is that Alumasc is ideally positioned to offer a single-source solution, fully warranted waterproofing and sustainable drainage solution that is integral to a system of this kind.

We do not offer drainage attenuation design as a standalone package to be used in combination with any non-Alumasc product.

Q2. What are the typical flow rates that can be achieved using an Alumasc BluRoof?

BluRoof is an engineered drainage approach that addresses the individual project requirements. Blue Roofs are calculated to a whole rainfall series not just a single value, as intensity will change with time and therefore providing a default flow rate without analysis is not practical.

Q3. What information is required to provide a Blue Roof calculation?

The following key project parameters should be assessed to ensure that they are taken into consideration within our calculation.

1. The total size of the applicable areas in m², and if any other areas are draining onto them, the size of them also. Roof plan
    preferably in .dwg format would be required if the size of area was not advised.

2. The plan size of the applicable void former area in m², if less than the total plan area.

3. Are there any height constraints that would restrict the depth of void former that can be accommodated within the
    proposed assembly.

4. Are there any project targets identified for the Blue Roof to achieve, for example:
    – A particular peak run off rate in litres per second (l/s).
    – The detention volume of water (m³) to be attenuated per roof area.
    – A particular % reduction in the site peak run-off rate


Alumasc offer a free Blue Roof design service and all enquiries should be sent to technical@alumascroofing.com

Blue Roof brochure download

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White House Works, Bold Road, Sutton, St Helens, Merseyside, WA9 4JG