Installation of Guttering and Gutter Brackets

A gutter is a system, not a single length of metal or plastic. Each part has to fit the next one:

• Gutter brackets carry the gutter and set its fall
• Gutter lengths are joined end to end with union pieces
• Stop ends close off the ends of each run
• The outlet lets the water drop into the downpipe
• Internal and external angles are needed when the roof is more than a simple pitched shape

Eaves guttering is the usual choice on houses with a pitched roof and an overhang. You can see it, it is easy to clean, and when something goes wrong the water spills over the front edge. With concealed or box gutters, a fault often means water inside the roof structure.

The order matters. If the outlet position or the run length is only worked out after the pieces are joined, several metres of gutter often have to come apart again.

1. Measure the eaves and decide where the downpipe will go. As a rough guide, one downpipe serves about 10 metres of gutter.
2. Fix the first bracket at the high point, usually at the end furthest from the downpipe.
3. Work out the drop: multiply the run length in metres by the chosen fall, usually 2 to 5 mm per metre. For an 8 metre run with a 3 mm fall, the drop is 24 mm.
4. Fix the last bracket next to the outlet lower by this amount, then stretch a string line between the two end brackets.
5. Fit the intermediate brackets exactly to the line. Bend long brackets with a bracket bender, not a hammer, so the coating is not damaged.
6. Cut the outlet hole at the low point, keeping the distance from the gutter end that the manufacturer specifies. Clean up the edges and turn them down slightly.
7. Lay the gutter into the brackets from the high point towards the outlet: slide the back edge in, then secure the front edge with the bracket clip.
8. Join the lengths with the system's unions and rubber seals, then fit and seal the stop ends.
9. Connect the downpipe and test with water.

Each bracket is fixed with at least two screws, long brackets usually with three. Screws should be stainless steel or galvanised. Ordinary black wood screws rust quickly outdoors.

Which gutter size to choose

Choose the size by the roof area the gutter has to drain, not by looks. What counts is the plan area, meaning the roof as seen from above, not the sloping surface. Every manufacturer publishes a sizing table for this. Larger family houses often use a 150 mm gutter. On steep roofs the water runs off faster, so going one size up is sensible.

Galvanised steel, aluminium, copper or plastic

• Galvanised and coated steel is common, strong and copes well with snow.
• Aluminium is light and does not rust, but it needs careful, precise workmanship.
• Copper and titanium zinc tend to be chosen for more demanding architecture or historic buildings.
• Plastic is quiet and light, and suits garages, carports and smaller houses. It expands a lot with heat, so it needs expansion joints. On shaded north-facing roofs in snowy areas, where snow lies for weeks, it is more vulnerable.

Half-round or square profile

A half-round gutter flushes itself out better, because dirt has no corners to collect in. A square or box profile of the same width holds more water and suits modern houses, but it needs more thorough cleaning. So pick the shape to match the house and the size to match the roof area.

Bracket types

Long rafter brackets are fixed to the rafters or battens before the roof covering goes on and give a very strong fixing. Short fascia brackets are screwed to the fascia board, so they can be fitted to a finished roof, but how much they can carry depends on the condition of the board. Always buy the brackets from the same manufacturer as the gutter. A difference of a few millimetres in the profile is enough to stop the gutter seating properly.

A new roof is the straightforward case: the brackets go on before the covering, the walls are not yet finished, and the tinsmith works from scaffolding that is already up. The job takes longer and costs more when there is:

• A two-storey house that needs scaffolding or a lift
• A complex roof with hips, dormers and several levels
• Old guttering and brackets to remove first
• A rotten or uneven fascia board that has to be repaired first
• A finished roof where long rafter brackets can no longer be used
• Restricted access, for example over a neighbour's land or a public footpath

Gutter fitting is work at height, so leave it to a tinsmith or roofer with proper equipment and fall protection. If you live in a flat, replacing the gutters is a matter for the building management or owners' association, not for individual owners. A like-for-like replacement usually needs no permit. If the house is a listed building, lies in a conservation area, or the appearance of the roof changes, check with your local building authority before work starts.

Most gutter problems come from details of the installation, not from the material. These are the mistakes seen again and again:

• No fall, or a fall the wrong way. Water stands in the gutter, dirt settles and the water freezes in winter.
• Brackets too far apart. The gutter sags under wet snow. Brackets are usually placed roughly every 50 to 80 cm. Plastic gutters and snowy areas need closer spacing, and the manufacturer gives the exact figure.
• Gutter fitted too high. In a heavy downpour the water shoots over the front edge and runs down the wall. The top edge should sit slightly below the line of the roof covering extended outwards.
• Joints relying on silicone alone. Sealant only supports the system's rubber seals. On its own it stops sealing after a few seasons.
• No allowance for expansion in plastic. In summer the gutter bows and the joints pull open. Unions usually have a mark that shows how big a gap to leave for the temperature on the day.
• Fitting in frosty weather. Below about 5 °C plastic becomes brittle and sealants do not bond well.
• Mixing parts from different manufacturers. A common cause of leaks.

Before you accept the work, run a hose into the far end of the gutter for at least a few minutes, then step back and look along it. Check that:

• Water flows steadily to the outlet with no puddles left behind
• No joints, stop ends or the outlet drip
• Water does not spill over the front edge at full flow
• The gutter looks straight from a distance, with no sags or waves
• Brackets are evenly spaced, including near the ends and on both sides of the outlet
• Brackets do not lift the roof covering or block the roof ventilation gap
• Screws are stainless steel or galvanised
• The site is tidy and the roof covering and walls are undamaged

If you can, photograph the brackets before the roof covering goes over them. The photos are useful for any complaint or later roof work.