16mm Triplewall Polycarbonate

We recommend a maximum sheet width of 800mm for 16mm without extra support. The manufacturer allows wider spans at light loads, but 800mm is the safe figure for a DIY roof. That figure covers the sheet alone, not the roof structure beneath it, so check your wind and snow exposure, or call the technical team if you are unsure.

Twinwall has two skins with a single row of air channels between them. Our 16mm is a three-wall sheet: three skins and two layers of trapped air. The extra layer slows heat loss, so 16mm loses about a fifth less heat than 10mm twinwall, and the sheet is stiffer across its width. The trade-off is slightly less light.

16mm is the right choice for a canopy, lean-to or covered seating area. For a heated conservatory you sit in year round, we suggest 25mm or thicker, because 25mm loses about a third less heat than 16mm. Some customers fit 16mm over a conservatory to keep the cost down, but expect higher heating bills in winter.

Fit 16mm sheets at a pitch of at least 5 degrees, and 10 degrees or more works better for run-off. Water and leaf debris clear faster on a steeper slope. Run the flutes, the hollow channels in the sheet, down the slope so condensation drains out through the breather tape at the bottom edge.

Clear 16mm passes about 76% of daylight, bronze about 35% and white opal about 25%. Opal passes the least but spreads it evenly, removing glare and hard shadows. Choose clear where you want brightness, bronze to cut glare on a sunny aspect, and opal for a soft, even light over a seating area.