10mm Twinwall Polycarbonate

We recommend a maximum sheet width of 700mm for 10mm twinwall without extra support. The manufacturer's tables allow wider spans at light loads, but 700mm is the safe figure for a DIY roof. Sheet width alone does not make a roof sound, so check your wind and snow exposure, or call the technical team before you order.

Yes. Fit 10mm twinwall at a pitch of at least 5 degrees, and 10 degrees or more works better for run-off. A steeper slope clears rainwater faster and gives dirt less chance to settle. The flutes, the hollow channels inside the sheet, must run down the slope so any condensation drains out at the bottom edge.

Clear 10mm twinwall passes about 79% of daylight, bronze about 35% and white opal about 30%. Clear suits growing spaces and anywhere you want maximum light. Bronze cuts glare and some solar heat. Opal spreads the light evenly and removes the hard shadows a clear sheet can cast, which many people prefer over a seating area.

One side only. The UV-protected face is marked by the printed protective film, and it must face the sun. Fitted the wrong way up, we have seen sheets yellow and crack within a couple of years. Fitted correctly, the sheet carries a ten-year warranty against loss of light transmission. Keep the film on until the sheet is in position.

10mm twinwall suits light-duty covers: a greenhouse, cold frame, shed roof, small porch or garden canopy. It is light to handle and economical, but it insulates less than 16mm, and we recommend sheets no wider than 700mm. For a lean-to you will use often, choose 16mm. For a conservatory you heat and sit in, go to 25mm or thicker.

What are pre-taped edges on multiwall polycarbonate sheets?

Pre-taped edges mean that protective tapes have already been applied to the open ends of your multiwall polycarbonate sheets before delivery, saving you time during installation.

At The Polycarbonate Store, our complimentary pre-taping service is available on 10mm, 16mm, 25mm, 32mm and 35mm twinwall and multiwall polycarbonate sheets.

The two open ends of the sheet's hollow channels (flutes) are taped differently:

• Top edge – Aluminium sealing tape: Solid silver tape seals the upper end of the flutes, helping prevent water, dirt and debris from entering.
• Bottom edge – Anti-dust breather tape: Helps prevent dust and insects from entering while allowing ventilation and moisture to escape, reducing the risk of condensation build-up.

For a standard sloping roof, the aluminium-taped edge must be positioned at the top, with the breather-taped edge at the bottom, towards the gutter. The tapes should remain in place during installation.

Important: Pre-taping only covers the two open flute ends, not all four sides of the sheet. It does not replace the need for PVC sheet end closures, which should be fitted over the taped edges to provide additional protection and a neat finish. Pre-taping also does not completely prevent condensation.

During preparation, approximately 10mm of protective film is removed from each taped end. This may leave a visible preparation line, which is normally concealed by the roofing accessories. If you need to trim a pre-taped sheet, the newly exposed flutes must be cleaned and re-taped correctly before installation.

For curved roofing or other applications, the required tape arrangement may differ. Please contact us before ordering if you are unsure.

For further information, read our full guide: What Do Pre-Taped Edges Mean on Multiwall Polycarbonate Sheets?