Minimum Freeboard Values
In gutters where overflow can enter the structure, it is necessary to have freeboard to allow for wave action, obstructions, and other unforeseen circumstances. Capacity Calculations allow for these minimum freeboard values.
Minimum Freeboard Values
| Gutter Type | Freeboard |
|---|---|
| Internal gutters | 30 mm |
| Secret gutters | 15 mm |
| Valleys > 8° | 15 mm |
| Valleys < 8° | 20 mm |
| Asymmetrical valleys | 20 mm |
| External Gutters with Overflow | No freeboard required |
| External gutters with no overflow | 15 mm |
/cop/roof-drainage/roof-drainage-design#minimum-freeboard-values
Revision Category:
3 - Substantial change to recommendation