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Eaves gutter

An eaves gutter is the gutter at the edge of an eaves overhang. How it's sized to the catchment and AEP rainfall, and how it differs from valley and box gutters.

By Chalkline. Last updated 28 May 2026. Verified 28 May 2026.

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An eaves gutter is the gutter hung at the lower edge of an eaves overhang to collect water running off the roof and feed it to the downpipes. It is the standard residential gutter, distinct from a valley gutter (which runs along the internal angle where two roof planes meet) and from a box gutter (which sits within the roof line, often between parapets, and carries a more concentrated flow).

What it does

  • Collects roof runoff at the eaves and delivers it to spigots that drop into the downpipes.
  • Sets the catchment unit for the drainage design: each gutter length is sized against the roof area it serves and the design rainfall intensity for the site.
  • Carries the eaves line where the roof meets the fascia, with the gutter front edge typically dropped below the roof line so any overshoot in heavy rain clears the eaves rather than overflowing inside.

How it is sized

NCC 2022 Housing Provisions Part 7.4 sets the residential rules for eaves-gutter sizing (see NCC drainage compliance):

  • The gutter is sized for a 5% AEP (annual exceedance probability) rainfall intensity for the site and the catchment area it serves.
  • An overflow provision (high-front gutter, overflow slots, or an external overflow device) is sized for a more severe 1% AEP event, so a blocked downpipe does not back water into the eaves and the ceiling.
  • The gutter must have continuous fall to the outlet so it drains rather than pools.

Profiles include quad, half-round, square-line, and high-front, each manufacturer’s range carrying a different cross-section and flow capacity.

Why it matters

A gutter undersized for the catchment is a leading source of internal water damage at the eaves: water overflows behind the fascia, soaks the eaves lining, and tracks into the ceiling. Get the catchment area, the AEP intensity, and the overflow provision right and the rest of the drainage falls into place.

Also known as: roof gutter, fascia gutter, quad/half-round/square gutter (by profile).

Category: Roofing / drainage

See also

Last updated: 2026-05-28. Verified: 2026-05-28. Quarterly review for currency.

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