11/29/2025
Eaves and Rain Gutter Construction — Six Major Types
California Wood Structure Eaves and Gutter Systems – An Analysis of Six Types
(Written from the perspective of a general contractor + California building code requirements)
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1｜Simplest Form (Simple Eave + Exposed Gutter)
Common in: Warehouses, sheds, factories, and accessory buildings where aesthetics are not a priority.
Key Construction Points
• Install a galvanized iron gutter directly alongside the rafters.
• Suspend with wire or gutter hangers.
• The roof overhangs by only about 2 inches.
• Uses a standard downspout for drainage.
California Code Highlights
• Exposed gutters must have a minimum positive slope of 1/16” per foot.
• CRC R903: Roof drainage must be directed away from the building to prevent ponding water.
• A metal drip edge is required at the wall connection; it's mandatory for new roofs in California.
Pros and Cons
✔ Cheap, simple, and fast to install.
✘ Prone to denting, short lifespan, and unattractive appearance.
✘ Not suitable for residential facades.
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2｜Flat Roof & Parapet (Flat Roof with Internal Drainage)
Common in: Commercial buildings, modern-style homes, and flat-top structures.
Key Construction Points
• Install a metal-lined sump on the inside of the parapet wall.
• Use an internal drainage system (Scupper → Conductor Head → Downspout).
• The roof deck must have a waterproof membrane (e.g., Torch-down, TPO, PVC).
• The sump is the lowest point, channeling water to the metal scupper outlet.
California Code Highlights
• CBC 1503: Flat roofs must have a minimum slope of 1/4” per foot.
• CBC 1503.4: An overflow scupper is required to prevent water ingress from clogged drains.
• Internal drains must have removable covers for maintenance.
Pros and Cons
✔ Clean, modern appearance.
✔ Gutters are not visible.
✘ High risk of clogs with internal drainage.
✘ Higher maintenance costs.
3｜Projecting Cornice (Overhanging Eave with Exposed Rafters and Integrated Metal Gutter)
Common in: Craftsman, traditional American, and exposed rafter-style homes.
Key Construction Points
• Rafters are left exposed.
• The underside is finished with T&G boards for a cohesive look.
• The gutter is closely integrated with the cornice, often using a formed metal channel.
• Cornice projection typically ranges from 12” to 24” depending on the design.
California Code Highlights
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