Practical points for fitting eaves gutter and downpipes so roof water is collected and carried away cleanly.
Rainwater (surface water) guttering looks simple, but it only works if it is set out and supported correctly. Use this as a revision checklist of good practice, then size the system from current guidance.
- Set the designed line. Use the manufacturer’s fall and capacity instructions; some layouts are rated level. Where a fall is specified, set it evenly towards the outlet without dropping below the roof-edge catching position. Avoid local sags.
- Position under the roof edge. Set the gutter so water shedding off the roof falls into it and is not thrown over the front in heavy rain.
- Support it properly. Use the selected profile’s bracket centres, fitting fixings and loading requirements. Check the fascia and supports, including any additional brackets required at joints, angles or stop ends.
- Make the joints. Assemble unions, angles and outlets so they seal and allow for thermal movement, as plastic gutter expands and contracts noticeably.
- Fit the downpipes. Run downpipes from the outlets down to the drainage point, clipped to the wall, with offsets (swan necks) to clear the eaves where needed.
- Discharge correctly. End the downpipe at a suitable point such as a gully, a back-inlet gully or a soakaway, keeping surface water separate from foul where the system is separate.
- Size for the roof. Calculate the effective roof area and design rainfall flow and check each gutter arm, outlet and downpipe. Provide the specified safe overflow route rather than assuming design sizing prevents overflow in every storm.
Maintain the designed line, support and seal the system and send the water to a suitable outfall. Confirm sizing and discharge options against Approved Document H.