Downpipe Spreaders

All downpipes that discharge onto a lower roof must have a spreader to dissipate energy and ensure wide distribution of the water. A spreader should be used over multiple troughs.

For corrugate, a spreader should not discharge into a lapped trough. When using the COP calculator, discharge may be into a lapped trough of a trapezoidal or a trough profile.

The area of discharge holes from a spreader should equal the cross-sectional area of the downpipe.

The Maximum Area Above Spreader Calculator enables users to determine the maximum upper roof area that a lower roof can discharge for a given combination of rainfall intensity, roofing profile, and lower roof pitch.

Downpipe Spreader design

Downpipe Spreader Design

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