Reviewed and updated: 17 October 2026. Original archive publication date retained.
A butterfly roof is an inverted roof form, with opposing surfaces falling towards an internal valley rather than rising to a central ridge. It can create a distinctive silhouette, but appearance is only one part of assessing a roof for a home.
Design the whole assembly
The roof shape needs to work with the building’s structure, insulation, weatherproofing and drainage. Ask the designer to show how water reaches outlets, what happens if an outlet becomes obstructed and how the relevant parts can be inspected and maintained.
RIBA’s project directory includes an architect’s example of an inverted butterfly roof forming part of an open-plan living space. That demonstrates a design use, not a universal performance advantage or a standard solution for every site.
Assess the particular building
For an existing roof, establish its construction, repair history and condition. A visually attractive valley may conceal details that need specialist inspection. Do not assume that changing the outer shape alone resolves a drainage defect.
For new work, obtain the necessary design and approval advice before comparing quotations. Ask each contractor to price the same specification, including access and future maintenance arrangements.
A butterfly roof is not automatically cheaper, greener or more valuable than another form. Its suitability depends on the actual design, workmanship and how the completed roof will be cared for.