Selecting the correct polycarbonate sheet thickness is critical for ensuring structural integrity, light transmission, and cost efficiency in your roofing or glazing project. This guide covers the key factors to consider when specifying polycarbonate sheets.

Thickness Options and Their Applications

Polycarbonate sheets are available in a wide range of thicknesses, each suited to different applications:

  • 2mm–3mm: Decorative applications, temporary structures, display cases
  • 4mm–6mm: Residential greenhouses, small carports, patio covers
  • 8mm–10mm: Commercial greenhouses, large carports, skylight glazing
  • 12mm–16mm: High-load applications, sports halls, industrial skylights
  • 20mm–25mm: Extreme load requirements, noise barriers, security glazing

Key Factors in Thickness Selection

1. Span Between Supports

The distance between purlins or support structures is the primary factor determining required thickness. As a general rule, longer spans require thicker sheets. For a 1.2m purlin spacing, 8mm twin-wall polycarbonate is typically the minimum recommended thickness.

2. Snow and Wind Load

In regions with heavy snowfall or high wind speeds, thicker sheets or multi-wall profiles are essential. Always consult local building codes for minimum load requirements.

3. Light Transmission Requirements

Thicker multi-wall sheets have lower light transmission than thinner solid sheets. Clear 4mm solid polycarbonate transmits approximately 88% of light, while 25mm multi-wall transmits around 50%.

Solid vs. Multi-Wall Polycarbonate

For most roofing applications, multi-wall (twin-wall or triple-wall) polycarbonate is preferred over solid sheets due to better thermal insulation and higher strength-to-weight ratio. Solid sheets are better for applications requiring maximum light transmission or optical clarity.

Conclusion

When in doubt, always specify one size thicker than the minimum calculated requirement. Contact Bonai’s technical team for project-specific recommendations — we provide free specification support for all orders.