Cross-Gabled Roof

A cross-gabled roof is formed when two or more gable roofs meet, usually at right angles, so that their ridges cross or join. It is the standard way to roof a building whose plan is L-shaped, T-shaped or cruciform, and it is extremely common in houses in North America, the UK, Australia and elsewhere. The equivalent arrangement with hipped roofs is called cross-hipped, or in UK usage, hip-and-valley.

Geometry

Where the two roofs meet, internal corners form valleys, and the main ridge may continue through or be met by the secondary ridge at a lower or equal height. Each wing ends in its own gable, so a cross-gabled house presents gables to two or more directions, which architects use to create variety in the elevations.

Construction

• Framing: valley rafters or valley boards on the main roof carry jack rafters of the intersecting roof. With trusses, the secondary roof is often built over the sheathing of the main roof using valley sets ("California framing" in North America).
• Valleys: the valleys need extra underlayment and an open, closed-cut or woven valley detail in shingles, or a lined valley in tile and slate.
• Ventilation: each roof section needs its own path for intake and exhaust air, which can be complicated by valley framing that blocks airflow.

Advantages

• Follows complex house plans and allows large attic spaces in each wing.
• Gable walls in each wing can carry windows and vents.
• Visual interest compared with a single gable.

Disadvantages

• More valleys mean more places where water concentrates and leaks can occur.
• Multiple gable ends share the wind vulnerability of simple gable roofs.
• Snow can drift into valleys and against higher roof sections.