A roof cornice is the decorative or functional moulding that forms the transition between the top of a building’s facade wall and the edge of the roof, projecting outward to direct rainwater away from the wall surface below.
Purpose and function
The primary function of a roof cornice is to protect the facade from water damage. By extending beyond the plane of the wall, the cornice throws rainwater clear of the brickwork or render, reducing staining, erosion, and damp penetration. In many traditional buildings the cornice also conceals the rafter feet and the junction between roof structure and wall, giving the roofline a clean, finished appearance.
Historically, cornices served as a strong visual element that defined the top of the facade and separated the wall from the roof. In classical architecture, the cornice is the uppermost part of the entablature and often features elaborate moulding profiles such as cyma recta, ovolo, and dentil courses.
Materials
Roof cornices can be made from a range of materials depending on the building style and era:
- Natural stone — limestone or sandstone, carved to profile, common on historic and monumental buildings.
- Brick — corbelled brick courses stepped outward to form a simple cornice, typical of traditional Dutch and Flemish architecture.
- Timber — painted or stained wooden mouldings, frequently seen on residential buildings.
- Precast concrete — a cost-effective option for modern construction that can replicate traditional profiles.
- GRP (glass-reinforced polyester) or EPS (expanded polystyrene) — lightweight replica cornices used in renovation and new build to achieve a period look without the weight.
Application
When designing or restoring a roof cornice, builders must ensure the projection is sufficient to protect the wall below while not creating excessive wind uplift loads. Proper flashing or drip details at the top of the cornice prevent water from running back toward the wall. On listed or heritage buildings, cornice repairs must match the original material, profile, and finish to satisfy conservation requirements.
Related terms
- Eaves
- Fascia board
- Soffit
- Gutter
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.