Roof drainage systems should be designed and detailed by a suitably qualified trade or professional in accordance with the BCA and the Australian Standards. Particular reference should be made to the correct sizing of gutter; quantity and placement of downpipes; and the provision of appropriate overflow devices.

In the design and detailing of a roof drainage system, consideration must be given to a range of factors such as:

• rainfall intensity
• roof catchment area
• gutter size/capacity
• gutter fall
• gutter outlets (sumps, rain heads, nozzles)
• downpipe size, quantity and placement
• overflow consideration
• material selection and

You can view information on the design of roof drainage systems in the brochure for your state:

LYSAGHT® Rainwater Solutions NSW Guide PDF (2.8 MB). Last updated 27 Feb 2019

LYSAGHT® Rainwater Solutions QLD Guide PDF (2.2 MB). Last updated 26 Aug 2016

LYSAGHT® Rainwater Solutions VIC/TAS Guide PDF (1.6 MB). Last updated 23 Jan 2019

LYSAGHT® Rainwater Solutions SA Guide PDF (1.6 MB). Last updated 15 Jun 2017

LYSAGHT® Rainwater Solutions WA Guide PDF (1.7 MB). Last updated 3 Jul 2018