Choosing the right thickness for a polycarbonate sheet is one of the first specification decisions on any roofing or facade project — and getting it wrong is expensive to fix after installation.
Why Thickness Matters
Thickness affects three things directly: impact resistance, light transmission, and how far the sheet can span between purlins without sagging. A thin sheet over-spanned will deflect visibly within a season; an over-specified thick sheet adds cost with no functional benefit.
General Guidelines by Application
- 4mm solid sheet — small canopies, signage, and short-span skylights
- 6–8mm multiwall — residential pergolas and greenhouse glazing
- 10–16mm multiwall — industrial roofing and wide-span commercial skylights
- 25mm+ multiwall — large-span structural roofing needing insulation value
A sheet specified purely by price, without checking the span table, is the single most common cause of early sagging we see reported by dealers.
Matching Thickness to Purlin Spacing
Every V-LITE multiwall profile has a published maximum purlin spacing for a given thickness and wind-load zone. Always confirm this against the actual site conditions rather than a neighbouring project, since wind zone and snow load change the safe span considerably.
Talk to Us Before You Order
If you are unsure which thickness fits your span and load conditions, share your drawing with our technical team before placing the order — a five-minute check at this stage avoids a costly reinstallation later.
