1. Key Factors Influencing Thickness Choice
Structural Role (Most Important Factor):
Retaining Walls or Load-Bearing Walls: If the wall is earth-retaining or supports significant load, the thickness must be determined by a structural engineer through calculations based on soil pressure, height, and span. Thickness can range from 6 mm to 20 mm or more in these cases.
Free-Standing Non-Load-Bearing Walls (e.g., garden screens, decorative walls): These primarily need to support their own weight and resist wind loads. Common thicknesses are lighter, typically between 3 mm and 8 mm.
Sculptures: The choice is highly artistic. For large, self-supporting sculptures, thicknesses of 6 mm to 12 mm are common to prevent flexing and ensure stability. Smaller sculptures might use 3 mm to 6 mm.
Sheet Size and Panel Stability:
A fundamental rule is that larger, unsupported panels require greater thickness to prevent oil-canning (a wavy, buckling appearance) and to resist vibration from wind.
For example, a large, flat panel might need to be 6-8 mm thick to feel rigid, while the same panel with frequent stiffeners (e.g., welded ribs or a folded hem) could be made from 3-4 mm sheet and achieve the same stability.
Fabrication and Forming Requirements:
Bending and Welding: Thicker plate (e.g., >10 mm) requires more powerful machinery for bending and cutting and greater skill for welding. Thinner sheets (3-6 mm) are much easier to form into curves and complex shapes, which is crucial for sculptures.
Edge Details: Thicker material allows for more dramatic beveling or profiling on edges for aesthetic effect.
Aesthetic Desired ("Heft" and Permanence):
The thickness contributes to the perceived mass and permanence of a structure. A 12 mm thick wall feels solid and monumental, while a 4 mm wall can feel more delicate and modern.
Corrosion Allowance:
While the patina protects the steel, a minimal loss of material over decades (on the order of microns per year) is considered. For a structure designed to last 50+ years, an extra 1-2 mm of thickness (the "corrosion allowance") may be added beyond the structural requirement, though this is often minor for weathering steel in atmospheric applications.
