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Polycarbonate sheets for a greenhouse

Updated: 23 October 2026

The pane has gone milky, or a football has gone through the glass, and you want something you can fit without a crate of horticultural glass. For a typical UK hobby greenhouse, polycarbonate sheets for a greenhouse start at 4 mm twin-wall, with 6 mm if you want a little more insulation. Use one solid 4 mm sheet only for a single glass-sized pane. Do not put a 1 mm roll on the roof. Prices and the light figures below are from the amazon.co.uk listings in our [polycarbonate sheet comparison](/hub/diy-supplies/polycarbonate-sheet), the RHS, and The Glazing Shop. We did not measure your greenhouse. A qualifying purchase can earn a commission at no extra cost to you.

The pane has gone milky, or a football has gone through the glass, and you want something you can fit without a crate of horticultural glass.

Our top picks

Panda Ant Panda Ant 4 mm solid sheet

Best overall

Panda Ant Panda Ant 4 mm solid sheet
7.6/10about £24.99
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CHEOAR CHEOAR 4 mm twin-wall 10-pack

Best value

CHEOAR CHEOAR 4 mm twin-wall 10-pack
7.4/10about £61.99
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SANJIAOJIA SANJIAOJIA sheet, 1 m × 2 m

Alternative

SANJIAOJIA SANJIAOJIA sheet, 1 m × 2 m
5.5/10about £32.90
View offer
On this page
  1. 1.What a greenhouse pane has to do
  2. 2.4 mm twin-wall, and when to step up
  3. 3.The two listings that can be greenhouse panes
  4. 4.Fitting only as it affects the plants

What a greenhouse pane has to do

A greenhouse pane has to let in enough light, survive a stray fork or a falling pot, and hold a bit of the day's heat. Glass still wins on clarity. The RHS puts glass at about 90% light transmission and clear polycarbonate at about 83%. Twin-wall adds a rib pattern and a little insulation, and it is the sheet that survives the knock that writes off a glass side. The RHS points out that the light drop can limit crops that want high light. Brett Martin's own 4 mm twin-wall datasheet lists 0.8 kg per square metre, for their sheet, not a marketplace pack. A lean-to on the house is not this job. Spans, 10 mm, and 16 mm belong on the polycarbonate sheet buying guide.

4 mm twin-wall, and when to step up

The Glazing Shop treats 4 mm twin-wall as the common greenhouse replacement. On their figures it is about 82% light transmission with a U-value of 3.8 W/m²K. Six millimetres is the next step, at about 80% light and 3.5 W/m²K. Do not paste Brett Martin's 3.90 W/m²K figure onto the CHEOAR pack. Choose 4 mm when the house is a standard hobby greenhouse. Step towards 6 mm when the house is exposed, you are heating it, or you want extra stiffness. The CHEOAR listing claims 89% light, above The Glazing Shop's 82% and the RHS figure of about 83%. That 89% is a seller claim, not a number we measured.
Panda Ant Panda Ant 4 mm solid sheet

Testsieger

Panda Ant Panda Ant 4 mm solid sheet
7.6/10about £24.99
View offer

The two listings that can be greenhouse panes

Two of the four listings can be greenhouse panes. The value route for several panels is the CHEOAR 10-pack, about 61 cm by 121 cm by 4 mm twin-wall, at £61.99, rated 4.9 from 23 reviews. The included-components field is NO, so you still buy tapes and fixings. One reviewer said the sheet was thinner than expected. The single-pane route is the solid Panda Ant board, 610 mm by 457 mm by 4 mm, at £24.99, rated 5.0 from six reviews. One buyer fitted two in place of broken greenhouse glass. The manufacturer field reads Exolon. It is a poor match if you hoped one board would skin a whole roof. The SANJIAOJIA rolls are about 1 mm. Do not treat a 1 mm roll as a greenhouse pane.

Fitting only as it affects the plants

The cut-and-fix sequence is on how to fit a polycarbonate sheet. Two parts of it change what the plants receive. The UV face goes out. If the coated face is inside, the sheet hazes and yellows. If the film has no print, do not guess. The flutes stay sealed at the top and breathing at the bottom, with the ribs running down the slope. Open channels fill with algae, and that grey stripe cuts more light than the small gap between 82% and 80% on a data sheet. Vacuum swarf out before you tape. Acrylic on a greenhouse roof is the wrong swap. The RHS notes that acrylic twin-wall is more brittle and tends to crack during fitting.

Common questions

Is 4 mm twin-wall enough for a UK hobby greenhouse?
For a typical hobby greenhouse, yes, when the existing bars support it. The Glazing Shop treats 4 mm twin-wall as the usual glass replacement, at about 82% light and a U-value of 3.8 W/m²K on their figures. It is not the sheet for a conservatory or a wide lean-to, which merchants move up to 10 mm or 16 mm.
When is 6 mm worth it?
When you want a little more insulation and stiffness and you can give up a little light. The Glazing Shop puts 6 mm at about 80% light and 3.5 W/m²K, against 82% and 3.8 for 4 mm. It is worth it on an exposed or heated house. It is not in this amazon.co.uk set, so buy it as a trade sheet.
Will plants get less light than under glass?
Usually, yes, compared with clean new glass. The RHS puts glass at about 90% and clear polycarbonate at about 83%, and says the drop can limit high-light crops. Dirty or broken glass is a different starting point. Twin-wall also draws a rib pattern across the bed. Do not expect the CHEOAR seller's 89% claim to match those merchant figures.
Can I use the thin roll on the roof?
No. The thin listings are about 1 mm, and reviewers report curl and a sheet that is too thin for a shed window. A greenhouse roof needs a flat 4 mm or 6 mm panel that can be taped and fixed. A roll is a cover you can bend, not a pane. Leaving it in the sun is not a promise that it will flatten.
Which listing replaces one broken glass pane?
The solid 610 mm by 457 mm by 4 mm Panda Ant sheet, at £24.99, if that is your glass size. One reviewer fitted two of them as greenhouse glass. The rating is 5.0 from only six reviews. If you are replacing a run of panels, the CHEOAR 10-pack at £61.99 is the closer buy, and it does not include tapes.
Will the sheet yellow?
It is much more likely to yellow if the UV face is fitted inside or if the film never told you which face was coated. Outdoor multiwall is coated on one side. Keep that side to the sun, and take the film off after fixing so it does not stick. Open flutes going green with algae will cut the light even when the plastic itself has not yellowed.

Related pages

Best polycarbonate sheet

Polycarbonate sheet vs acrylic

Polycarbonate sheet

Polycarbonate sheet buying guide for span and type

How to fit polycarbonate sheet without standing on it

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Listings captured 19 October 2026. Updated 23 October 2026.

  1. The Glazing Shop thickness guide (retrieved 19 October 2026)
  2. The Glazing Shop buyers guide (retrieved 19 October 2026)
  3. BSI, BS EN 16153:2013+A1:2015 (retrieved 19 October 2026)
  4. Approved Document B amendments (retrieved 19 October 2026)
  5. Brett Martin TB413 (retrieved 19 October 2026)
  6. Brett Martin Marlon ST (retrieved 19 October 2026)
  7. RHS: choosing greenhouses (retrieved 19 October 2026)
  8. Class E, GPDO 2015 (retrieved 19 October 2026)
  9. The Polycarbonate Store twin-wall (retrieved 19 October 2026)