Roof Profile Flow Capacity
Theoretical calculation has shown that apart from Corrugate and V-Rib, all other Dimond roofing profiles are capable of accommodating the water from the most intense downpours (200mm/hr), even where total roof runs (ridge to gutter) reach 200m.
The lower rib, multi channel profiles Corrugate and V-Rib, have the following capacity restrictions for the total run of roof.
| Profile | Max. Channel length (m) | Channel width (mm) |
| Corrugate | 25 | 76 |
| V-Rib | 80 | 101.6 |
These are the recommended maximum length s(from ridge to gutter) of the water channels to avoid side lap leakage.
Where water flows are interrupted (e.g. penetrations, or where water is accumulated and deposited from an upper roof onto a lower roof ), care must be taken to calculate the total length of channel within the catchment area that will be diverted to one roofing channel. This calculated length must then be added to the length of channel (ridge to gutter) the water will be diverted into. The total length must not exceed the calculated capacity (maximum channel length) of the profile used. Where it is anticipated that the profile capacity will be exceeded (thereby causing a risk of water flowing under the side flashing), steps must be taken to divert the water flow to a greater number of channels, or select a profile that can better handle the anticipated water flow.
When using all other Dimond profiles, please contact Dimond if the anticipated catchment area (channel length) exceeds 200m.
E.g. where a penetration interrupts the water flow on Dimond Corrugate
Width of penetration | 1m |
|---|---|
Divided by the width of a Corrugate channel (76mm) | 1 / 0.76mm = 13.15 channels |
Take half this number as only 1/2 the catchment area will be diverted into the channel beside the penetration | 7 channels |
Multiplied by the run of roof from ridge to the back of the penetration | 7 x 3.5m = 25.5m |
Add the length of one full channel (ridge to gutter), as this channel will carry the water collected from behind the penetration to the gutter. | 25.5 + 8 = 33.5m |
As the total amount of channel behind the penetration plus one channel from ridge to gutter exceeds the recommended maximum length of Corrugate channel, the water behind the penetration will need to be diverted into more than one channel to avoid the possibility of side lap leakage, or an alternative profile chosen.
