Deep flow vs standard gutters: which one a veranda roof needs

What the difference actually is

A standard domestic gutter is a shallow half round or similar profile. A deep flow gutter is deeper and usually a little wider, so its cross section is bigger. More cross section means more water can sit in the gutter and flow along it to the outlet during a heavy downpour. Both are sold in the same lengths and connect to downpipes in the same way; the difference is capacity.

How veranda gutters differ from house gutters

Many aluminium veranda systems have the gutter built into the front beam, with the water running down inside one or more of the posts. In that case the gutter size is part of the system, and the choice is more about how many posts carry downpipes and where the water discharges. Where a separate gutter is fitted, standard and deep flow profiles are both options.

When a standard gutter is enough

A modest roof with a short run to a single outlet, draining to an open area or a nearby drain, rarely needs more than a standard gutter. Glass and polycarbonate roofs shed water quickly, so the gutter has to be able to take a sudden rush, but on a small roof that volume is manageable.

When to go deeper or add a downpipe

The signs that point toward more capacity are mostly about the size of the roof and what else feeds into it.

• A wide roof with a long run to one outlet
• A house roof or valley that already drains onto the veranda roof
• Overflow that would land on a doorway, path or seating
• Trees nearby that will partly block the gutter with leaves
• A low pitch, where water leaves the roof more slowly

Downpipes matter as much as depth

A deeper gutter carries more water, but a gutter can only empty as fast as its outlets let it. Adding a second downpipe, so the run to each outlet is halved, often does more than changing the profile. On aluminium verandas this can mean running water down two posts rather than one. We look at both on survey.

Where the water goes

However big the gutter, the water has to end up somewhere sensible: an existing drain, a soakaway or a water butt, not the patio in front of the back door. If the structure sits near a boundary, the gutter must not overhang or discharge onto the neighbour's land. Our guides to veranda drainage and to gutters on shared boundaries cover those points.

If your gutter already overflows

Before blaming the gutter size, check for blockages at the outlet, a gutter that has lost its fall and holds water, or leaves collecting at a corner. Those cause far more overflows than undersized profiles. If it is clear, level and still overflows in heavy rain, extra capacity or another outlet is the fix. Our veranda gutter overflowing guide walks through the checks.