Rainwater goods
Guttering and downpipes
Half-round, ogee or deepflow in uPVC, aluminium or cast iron, bracketed at 800 mm centres and sized to the roof area that drains into it.
How it works
Gutter size is arithmetic, not preference. BS EN 12056-3 sizes the run from the effective roof area, the rainfall intensity for your postcode and the number of outlets. A 112 mm half-round on a big rear slope with one outlet will overshoot in every heavy shower no matter how well it is bracketed; 150 mm deepflow with two outlets will not.
Guttering is also why a lot of fascia rots. Brackets work loose, the gutter tips back, and water sits against the board. Brackets at 800 mm centres screwed into sound timber hold the fall, and the fall is what makes a gutter a gutter rather than a trough.
A gutter that overshoots is usually undersized, not blocked. Measure the roof area before blaming the leaves.
- Profile
- Half-round 112 mm, ogee 110 mm or deepflow 150 mm
- Material
- uPVC, powder-coated aluminium or cast iron
- Downpipe
- 68 mm or 110 mm, sized to the run
- Brackets
- 800 mm centres, into sound timber
- Fall
- 1:600 to the outlet
- Sizing
- BS EN 12056-3, from effective roof area
