Square or half-round gutters: choosing a system for your roof

A square gutter gives the eaves a crisp outline. It can complement a plain façade, simple window frames and dark roofing. A half-round gutter has a softer outline and works with traditional roof forms as well. View the colour beside the soffit and downpipes as well as the roof covering.

Square describes the cross-section. Concealed describes how the drainage is installed. A square gutter can be fully exposed. Enclosing the gutter makes access for maintenance and protection against leakage particularly important. Develop this detail at the design stage if you want the gutter out of sight.

Size the system for the roof area, its geometry and the design rainfall intensity. Run length, outlet position, pipe cross-sections and changes in direction all affect performance. Even a large gutter can overflow at a poorly positioned or undersized outlet. Check the path to the receiving drain or storage system.

External width alone is a poor basis for comparing systems. The available flow area and the way the gutter feeds the outlet can differ. Use sizing tables for the chosen product. A large roof may require several outlets, and a larger gutter still leaves a bottleneck if the downpipe is too narrow.

Coated steel and plastic are two common choices. Their thermal movement and installation requirements differ. Check how each connector accommodates movement and how the components are fixed. Use compatible parts. A small difference in gasket shape between two similar-looking fittings may show up only in rain.

Protect steel coatings when cutting and fitting. With plastic, pay close attention to expansion allowances and joint clearances. Both materials need leaves removed and joints inspected. For dark gutters exposed to direct sun, check provision for thermal movement as part of the colour choice.

Typical faults include poor alignment with the eaves, incorrect bracket spacing and joints that cannot move. Position the gutter to catch runoff while allowing for snow sliding from the roof. Provide any required snow-retention measures separately and select brackets and supports for the system and roof conditions.

Follow the system instructions for fall, expansion joints and outlet positions. Exposed and concealed gutters can have different requirements. A connector clamped too tightly can restrict movement. At handover check for standing water and trace the flow through the downpipes and final connection. Inspect the pipe brackets as well.

Access and the surroundings generally matter more for cleaning than the cross-section. Leaves enter either gutter near trees. Guards can intercept coarse debris while fine sediment still collects. Check the outlets, bends and gullies, where blockages can form.

For a gutter screened by a fascia, establish how to remove the cover. Provide safe access for inspection and cleaning. From ground level, note where overflow occurs during rain, then arrange a closer inspection from a safe working position when conditions allow. Keep off a wet roof during a downpour.

Count gutters, downpipes, outlets, corners, stop ends, brackets, clips and connectors. Concealed systems also need enclosure components and protection where they adjoin the façade. Price the whole set, check availability and replacement costs, and keep the parts schedule.

Send the supplier a roof plan with eaves lengths, suggested downpipe positions and the intended destination for rainwater. Obtain a system sized for that roof, then compare appearance and price. Either cross-section should be part of a continuous route that takes runoff to the intended discharge point.