Corrugated sheet iron in roofing: Which statements about manufacture, properties, protection, and typical use of corrugated iron sheets are correct?

Introduction / Context:
Corrugated iron (or steel) sheets are ubiquitous in roofing and cladding. Corrugations increase structural efficiency, and galvanising mitigates corrosion. Understanding how they are made and why they are used helps in material selection for lightweight roofing systems.

Given Data / Assumptions:

• Manufacturing uses mechanical corrugating rollers.
• The structural role is primarily roofing on pitched structures.
• Protection is via zinc galvanising in most common products.

Concept / Approach:
Corrugation is a geometric stiffening method. The sinusoidal/trapezoidal profile increases section modulus and moment of inertia without adding thickness, thus improving resistance to bending and buckling. Zinc galvanising provides sacrificial protection against corrosion, extending service life in outdoor exposure. Sloping roofs shed rain effectively and suit lapped, lightweight sheets.

Step-by-Step Solution:

Verification / Alternative check:
Product datasheets and roofing handbooks confirm improved structural performance and standard galvanised finishes, with typical use on industrial, agricultural, and residential lean-to or pitched roofs.

Why Other Options Are Wrong:
Options A–D are each correct; thus the comprehensive and most accurate choice is “All of the above.”

Common Pitfalls:

• Assuming strength gain requires thicker metal; shape alone contributes significantly.
• Ignoring the need for corrosion protection in coastal/industrial atmospheres.

Final Answer:
All of the above