A gutter is chosen on three things: how much water it has to carry, what the building looks like, and how long you want it to last. British houses carry half round, ogee, square and deep flow profiles in plastic, aluminium, steel, cast iron and copper, and the choice is not only aesthetic because the profiles carry different volumes.
The profiles and what they carry
Half round is the traditional shape and the most common. Ogee, with its decorative front face, suits period frontages and is widely used on newer houses too. Square reads as modern. Deep flow profiles exist because a standard half round is not always enough for a large or steep roof, particularly where a house has been extended and more area now drains into the same run. Choosing by looks alone is how an undersized gutter gets fitted to a roof that overwhelms it.
Materials, honestly compared
Plastic is cheap, light, and the default on most houses, with ultraviolet degradation and joint seals as its weaknesses. Coated aluminium is often seamless, formed on site in one length, which removes the joints that fail. Steel is strong and depends on its coating. Cast iron is heavy, long lived, needs painting and is frequently what a period or listed property should keep. Copper is the most expensive, needs no coating, weathers to a green patina and lasts generations, which is why it appears on buildings whose owners are thinking in decades.
Roof and gutter work as one system
Water leaves the covering at the tile line, has to land in the gutter rather than behind it, and reaches the downpipe by falling along the run. Get the gutter too low and driven rain overshoots it. Too high and it fouls the tiles. Get the underlay dressed short of the gutter and water runs behind the fascia instead of into the channel. That last one is a common and invisible defect on re roofed houses.
Below the downpipe: the gully gutter and the soakaway
At the bottom the downpipe discharges either into a gulley connected to a drain or onto a shoe over a soakaway. A gulley silts up and is a frequent cause of water backing up around a wall base, and it is the part of the system nobody looks at. Where the discharge is to a soakaway it has to be far enough from the building and sized for the roof area, which Approved Document H sets out.
Gutter flashing, where the gutter cannot reach
Some junctions cannot be drained by a gutter and are sealed instead. Where a roof abuts a wall, where a lean to meets the house, or where a gutter run ends against brickwork, a flashing carries the water out onto the covering. Lead is traditional and durable; proprietary substitutes are lighter and easier to form. A mortar fillet used instead of a flashing will crack, and it is one of the most common defects found on older British roofs.
Questions people ask about roof guttering
Is copper guttering worth the cost?
On a building you intend to keep, and where the look is wanted, it is a genuine long life choice that needs no painting. On an ordinary house it is a considerable premium over coated aluminium for a similar service life.
What size gutter do I need?
It follows from the roof area draining into the run and the outlet positions rather than from the length. A contractor who asks about the roof area, and about any extension added since, is sizing it properly.
Can I mix materials on one house?
Functionally yes, visually it usually shows, and joining dissimilar metals can cause corrosion at the junction. Keep a single elevation consistent at the least.