Copper gutters fail for boringly predictable reasons: undersized outlets, no expansion allowance, cold solder joints and mixed-metal fixings. This guide walks through the six stages of a copper gutter installation the way we specify it on European projects — from rainfall calculation to flood-testing on handover.
1. Size the gutter and outlets before anything else
Copper gutter installation starts on paper. Calculate the effective roof area, apply the local design rainfall intensity, and size the trough and outlets to EN 12056-3. Undersized outlets — not undersized gutters — cause most overflow complaints on heritage restorations.
- Half-round 125 mm suits roof areas up to roughly 60 m² with one central outlet.
- Add a second outlet or a conductor head rather than widening the trough on long runs.
- Use 0.6–0.7 mm copper for domestic work and 0.8 mm where snow or ladder loads apply.
2. Set the fall and bracket spacing
Strike a chalk line from the high point to the outlet before fixing a single bracket. Consistent fall keeps standing water out of the seams, which is what extends the life of the solder joints far more than the copper thickness does.
- Fall of 1:350 to 1:600 — around 3 mm per metre — is the practical range.
- Bracket spacing of 500–600 mm; reduce to 400 mm in snow regions.
- Set a bracket within 150 mm of each joint, stop end and outlet.
3. Allow for expansion — copper moves
Copper expands roughly 1.7 mm per metre per 100 °C. On any run longer than about 8 metres, a rigidly fixed gutter will tear its own seams within a few seasons. Expansion joints are not optional detailing; they are structural.
- Fit an EPDM-sealed expansion joint every 8–10 m and at every change of direction.
- Fix the run at its midpoint and let it move toward the joints in both directions.
- Leave 5–8 mm clearance where the gutter passes fascia returns or masonry.
4. Soldering technique that survives the first winter
Soldered joints outperform sealant on copper drainage — but only when the surface preparation is right. Clean, flux, pre-tin and heat the parent metal rather than the solder.
- Abrade both faces to bright metal and flux immediately; oxide forms within minutes.
- Use 50/50 or lead-free tin-copper solder with a 25 mm minimum lap.
- Heat the copper until it draws the solder through the lap by capillary action; do not puddle.
- Wash flux residue off with clean water so it does not stain the developing patina.
5. Fixings and galvanic isolation
Mixed metals are the single most common failure we are called to inspect. Copper is noble; anything less noble in contact with it, or downstream of its runoff, will corrode.
- Use copper, brass or stainless steel fixings only — never galvanised or aluminium.
- Never discharge copper runoff onto zinc, aluminium or galvanised steel below.
- Isolate copper from steel structure with an EPDM or bitumen separation strip.
6. Commissioning and patina expectations
Flood-test every run before the scaffold comes down, and set the client's expectations about appearance. New copper is bright pink-orange, darkens to brown within months and reaches its green patina over decades depending on exposure.
- Flood-test to the outlet and check every joint and bracket for weep.
- Remove all swarf and steel-wool debris; embedded ferrous particles cause rust freckling.
- Offer pre-patinated stock where the client needs a uniform finish from day one.
Specifying a copper drainage system?
Send your drawings or specifications — we'll quote within two working days and supply shop drawings, fixings schedules and an installation manual with every system.