Do Plastic Corrugated Roofs Need Flashing?

Updated March 23, 2017

Corrugated plastic can be a low-maintenance, cost-effective choice of roofing material, and with careful installation it can provide shelter for a long time. The protection provided by flashing will make a roof last a lot longer.

What Is Flashing?

"Flashing" is the term used for protection provided on roofs where there is a junction in roof angles or a break in the roof. This would include the area around chimneys, at the apex of roofs or where a roof meets a wall.

Why It's Needed

Ineffective protection against water ingress causes leaks. Allowing water to regularly seep into the structure supporting the roof or to pool at any section of a roof will cause damage and rotting.


If a corrugated roof has a slight pitch or incline, splashback can occur. This can happen when rainwater splashes back up the channel created between the corrugated plastic and a flat layer of flashing. Water can then seep into the supports under that area of roof and cause dampness, eventually rotting the structure. Using either a filler, shaped flashing or malleable flashing to close off the channels of water ingress will remove this problem.

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About the Author

Louise Jones has been a technical writer since 2006 and is the director of a technical writing company, providing literature for U.K. construction firms such as MITIE and Balfour Beatty. Her work also appears on various websites, focusing on business and technical articles. Jones has a postgraduate certificate in education and has been trained in information technology. She studied English at Cambridge University.