The roof is an irregular shape, consisting of forms that are not of regular configuration.

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Irregular curved roof, Experience Music Project Museum, Seattle, USA (S. Brzev)

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An irregular roof, an arrangement of multiple roof shapes and pitches on a single building, New Zealand (A. Charleson)

The roof is a complex combination of roof forms with a degree of regularity such as symmetry.

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Complex regular roof, a symmetrical arrangement of multiple pitched gable roofs, New Zealand (A Charleson).

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Complex regular roof, a repeating arrangement of multiple pitched gable roofs, New Zealand (A Charleson).

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Complex regular roof, Phom Penh, Cambodia (C. Scawthorn)

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A school building in Padang, Indonesia - roof form derives from water buffalo horn (C. Scawthorn)

Cast-in-place concrete joists with hollow clay tiles and cast-in-place reinforced concrete topping, sometimes overlaid with roofing. These roofs may or may not have reinforced concrete ring beams at the perimeter.

Hollow clay tiles with cast-in-place concrete joists and topping, Slovenia (WHE Report 73)

Hollow clay tiles with cast-in-place concrete joists and topping, Slovenia (M. Lutman and M. Tomazevic, World Housing Encyclopedia Report 73)

Prefabricated reinforced hollow clay tile beams, with reinforced concrete ring beams, Italy (Maffei et al., 2006)

Prefabricated reinforced hollow clay tile beams, with reinforced concrete ring beams, Italy (Maffei et al., EERI, 2006)

Cast-in-place concrete joists with hollow clay tiles and cast-in-place reinforced concrete topping, sometimes overlaid with flooring. These floors may or may not have reinforced concrete ring beams at the perimeter.

Hollow clay tiles with cast-in-place concrete joists and topping, Slovenia (WHE Report 73)

Hollow clay tiles with cast-in-place concrete joists and topping, Slovenia (M. Lutman and M. Tomazevic, World Housing Encyclopedia Report 73)

Prefabricated reinforced hollow clay tile beams, with reinforced concrete ring beams, Italy (Maffei et al., 2006)

Prefabricated reinforced hollow clay tile beams, with reinforced concrete ring beams, Italy (Maffei et al., EERI, 2006)

Reinforced concrete cast onto steel decking, supported by beams or loadbearing walls.

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Composite steel deck and concrete slab (SteelDecking, UK)

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Steel trusses (open web steel joists) supporting composite steel and concrete floor system, Canada (S. Brzev)

Steel beams supporting composite steel and concrete deck flooring, USA (S. Brzev)

Steel beams supporting composite steel and concrete deck floor, USA (S. Brzev)