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Polycarbonate greenhouse panels that fit the frame

Updated: October 2026

A pane has cracked, and you want polycarbonate greenhouse panels in the same aluminium bars. The new sheet has to match the opening and the clip. A title that says 4 ft and a bullet that says 120 cm are not a measurement until you have taped the empty slot. Tapes and the UV face are on [how to fit twinwall polycarbonate](/hub/diy-supplies/twinwall-polycarbonate/sub/twinwall-polycarbonate-how-to-fit). The packs are on the [twinwall polycarbonate comparison](/hub/diy-supplies/twinwall-polycarbonate). Peter F. used UK glass sizes, clip listings, and the extracts on 16 October 2026. If you buy through our links, a qualifying purchase can earn us a commission at no extra cost to you.

A pane has cracked, and you want polycarbonate greenhouse panels in the same aluminium bars. The new sheet has to match the opening and the clip.

Our top picks

Warmfay Warmfay 10-pack 4 mm

Best overall

Warmfay Warmfay 10-pack 4 mm
5.6/10about £54.99
View offer
TEOV TEOV 14-pack 4 mm

Rank 2

TEOV TEOV 14-pack 4 mm
6.8/10about £62.29
View offer
CHEOAR CHEOAR 10-pack 4 mm

Alternative

CHEOAR CHEOAR 10-pack 4 mm
6.0/10about £61.99
View offer
On this page
  1. 1.Measure the pane you have
  2. 2.Clips and thickness
  3. 3.Which packs in this set are greenhouse-shaped
  4. 4.Packs that are not a 610 mm pane

Measure the pane you have

Take the broken pane out and measure the opening in millimetres, then the thickness the clip was made for. Horticultural glass in the UK is commonly 610 × 610 mm, 610 × 457 mm, or 730 × 1422 mm, in 3 mm glass. Me and My Glass quotes a cutting tolerance of about ±2 mm. Your house may be none of those three. The tape is the specification. On glass sellers, two foot means 610 mm. On some packs, 2 ft sits next to 600 mm, which is 10 mm narrower. Four feet on a title is often 1200 mm in the bullet, not 1220 mm. A 600 mm sheet can drop through a 610 mm slot. A spring clip cannot make a narrow sheet wider. Which thickness you needed is on the buying guide.

Clips and thickness

Omega’s W-clip is stated for 3 mm glass or 4 mm twinwall. That is the clip many aluminium houses already use. A 4 mm twinwall pane in that clip is the swap the clip maker describes. A 6 mm sheet in the same clip is a different experiment. One UK review in the UMIG extract says 6 mm stayed put after 4 mm panes blew out. Another text in the same dump calls the panels floppy. Both lines sit in one file that is also on the 12-pack. One retailer says a clip about every 12 inches. That is their line, not a British Standard. Match the clips already on a full pane. Extra clips will not hold a sheet that is 10 mm too narrow. Use 6 mm when the bar and the clip are made for it.
Warmfay Warmfay 10-pack 4 mm

Testsieger

Warmfay Warmfay 10-pack 4 mm
5.6/10about £54.99
View offer

Which packs in this set are greenhouse-shaped

CHEOAR’s 4 mm pack, B0F94D8L99, at £61.99, states 61 × 121 cm. That is the 610 mm width. Ten sheets, 5.72 kg, no fixings in the box. The 4.9 from 23 is shared with the 6 mm CHEOAR, so read it once. If your tape says about 610 mm, this is the listed size that matches the module. Your measurement still decides. The 6 mm CHEOAR, B0F94CP53Q, at £71.99, is the same width and a heavier 8.1 kg pack. Use it when the slot is wider than 4 mm. Warmfay, B0F9PHRC24, and TEOV, B0GXDZ5W59, are both 1210 × 605 mm at 4 mm, so both are 5 mm narrower than 610 mm. How those two are split is on the best twinwall polycarbonate page.

Packs that are not a 610 mm pane

UMIG’s 6-pack states 120 × 60 cm, with a model code that still says 4MM. The 12-pack’s title, bullet, and highlight disagree on length. Neither is a clean 610 mm pane. The Truly PVC sheet is one 10 mm opal panel, 2.1 × 4 m, and it will not enter a 4 mm clip. The generic 1 × 3 m sheet does not state twin-wall or a thickness. Measure, match 4 mm unless the clip is made for thicker, then pick the pack whose millimetres agree.

Common questions

Can I swap glass for 4 mm twinwall in the same clips?
Often, when the clip is the type Omega states for 3 mm glass or 4 mm twinwall, and the new sheet matches the opening. A 6 mm sheet in a 4 mm W-clip is not that swap. Read the clip you already have before you order.
Will a 600 mm sheet sit in a 610 mm bar?
It is 10 mm narrower than the module. A 605 mm pack is 5 mm narrower. Glass sellers talk about ±2 mm. A clip cannot stretch the sheet. In a slot cut for 24 inch glass, about 610 mm, a 600 mm pane can drop through. If the opening is 610 mm, buy a 610 mm sheet.
Is 6 mm always better in wind?
No. One UK review said 6 mm stayed after 4 mm blew out. The same dump calls panels floppy, and Omega’s W-clip is specified for 4 mm twinwall. Use 6 mm when the slot and the clip are made for it. Extra thickness does not fix a width error.
How many clips on a pane?
Match the pattern already on the house. One retailer says about every 12 inches, and that is their line, not a standard. Replace missing clips. Do not expect extra clips to hold a sheet that is too narrow for the bar.
Do I tape a small greenhouse pane?
Yes, if the flutes are open at the ends. Blanking tape goes on the top, breather tape on the bottom, and the UV face stays outwards. None of the packs in this set includes that tape, so it is a separate buy. The steps, and which silicone to avoid, are on the fitting page.
What if the title says 4 ft and the bullet says 1200 mm?
Use the millimetre line you can check, and only if the page has one such line. Four feet is often 1200 × 600 mm on the same listing, while glass sellers mean 610 mm by two foot. If the title, the bullet, and a highlight disagree, do not order.
Is opal right for crops?
No. Opal is a shade. On trade 10 mm figures it is about 30% light. A crop house wants clear 4 mm or 6 mm that fits the slot. The 2.1 × 4 m opal sheet in this set is a canopy panel, not a replacement pane.

Related pages

Twinwall vs solid polycarbonate

Twinwall polycarbonate

Best twinwall polycarbonate for a measured UK slot

Twinwall polycarbonate sheets: what to order in the UK

How to fit twinwall polycarbonate on a UK greenhouse

Sources

Public UK sources on the product standard, fire classification, outbuildings, and the description of goods. Prices, stars, and review counts are the amazon.co.uk figures in the extracts. The Polycarbonate Store prices are from 16 October 2026. Prices move.

  1. BS EN 16153:2013+A1:2015, light-transmitting flat multiwall polycarbonate sheets (retrieved 16 October 2026)
  2. Approved Document B, 2025 amendments (retrieved 16 October 2026)
  3. GPDO 2015, Schedule 2, Class E, buildings incidental to a dwellinghouse (retrieved 16 October 2026)
  4. Consumer Rights Act 2015, section 11, goods to match the description (retrieved 16 October 2026)
  5. Palram SUNLITE technical guide (retrieved 16 October 2026)
  6. The Polycarbonate Store, twinwall polycarbonate (retrieved 16 October 2026)
  7. Marlon ST installation guide (retrieved 16 October 2026)
  8. Omega greenhouse glazing W spring clip, pack of 100 (retrieved 16 October 2026)