Polycarbonate or polythene on a lean-to greenhouse
Updated: 21 October 2026
You are looking at two products that both get called plastic, and the prices are not in the same bracket. A polycarbonate or polythene greenhouse choice in this set is between a sewn polyethylene cover at about £37 to £60 and a panel kit at £157.69. The covers are the VOUNOT houses at £36.99 and £45.99, both printed at 135 g/m², and the Ohuhu at £59.99, which states polyethylene and does not state a grams-per-square-metre figure. The panels are the Outsunny, nominal thickness 0.4 cm. Those figures come from the amazon.co.uk capture of 19 October 2026 in the [lean-to greenhouse comparison](/hub/raised-beds-greenhouses-and-compost/lean-to-greenhouse). Peter F. used the listings and public UK material notes. A U-value was not measured. A qualifying purchase can earn a commission at no extra cost to you.
You are looking at two products that both get called plastic, and the prices are not in the same bracket.
You are looking at two products that both get called plastic, and the prices are not in the same bracket. A polycarbonate or polythene greenhouse choice in this set is between a sewn polyethylene cover at about £37 to £60 and a panel kit at £157.69. The covers are the VOUNOT houses at £36.99 and £45.99, both printed at 135 g/m², and the Ohuhu at £59.99, which states polyethylene and does not state a grams-per-square-metre figure. The panels are the Outsunny, nominal thickness 0.4 cm. Those figures come from the amazon.co.uk capture of 19 October 2026 in the lean-to greenhouse comparison. Peter F. used the listings and public UK material notes. A U-value was not measured. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Skin | Printed spec | Vent | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Ohuhu Ohuhu 210 cm lean-to greenhouse | Polyethylene cover | gsm not stated | 2 mesh windows | 8.2 | about £59.99 | View offer |
| Best value |  VOUNOT VOUNOT 200 cm lean-to greenhouse | HDPE cover | 135 g/m² | 1 mesh vent | 8.2 | about £36.99 | View offer |
| Alternative |  Outsunny Outsunny 6 × 4 ft lean-to greenhouse | Polycarbonate panels | 0.4 cm nominal | 1 roof vent | 7.2 | about £157.69 | View offer |
On this page
What each listing prints
A 135 g/m² cover, a polyethylene sheet with no weight printed, and a 0.4 cm polycarbonate panel are not one material. The VOUNOT bullets say high-density polyethylene at 135 g/m² on both the 200 cm and the 300 cm listing. The Ohuhu bullets say polyethylene and stop there, so you cannot assume it is also 135 g/m². The Outsunny field says polycarbonate at a nominal 0.4 cm, which is 4 mm if you convert the unit. That is not the same claim as 6 mm twin-wall, and the file does not say twin-wall.
Horticultural tunnel film at 180 or 200 micron, sold by firms such as Northern Polytunnels for a different structure, is not a spare skin for these walk-in covers. One Ohuhu reviewer looked for a replacement cover and did not find one on the listing. Glass is the boundary, not a third product in this set. GardenSite calls polycarbonate the safer option against horticultural glass in its own FAQ. Toughened safety glass has its own specification. Do not read that as a test of the Outsunny sheet.
Life, without a fake promise
Growsave, writing about greenhouse materials in general, says single-sheet polyethylene can last up to about five years and less without UV stabilisation, and that horticultural polycarbonate sheet often lasts 10 to 15 years. It also warns that many polycarbonate sheets are not made for greenhouses. Greenhouse Stores, a seller, puts thin single-skin plastic at about three to five years as a seasonal product, and says twin-wall yellows over about 10 to 15 years. Those ranges are not a test of B09RSNJ3T4, and they are not a test of a 135 g/m² sewn cover.
Do not write this polycarbonate lasts 15 years on the Outsunny. Do not write this cover lasts five winters on the VOUNOT. What the reviews do say is narrower. In the shared VOUNOT file a zip left the cover, in one case after a week, and the skin was not waterproof enough for stored tools. On the Ohuhu, one cover started to break up after a season. A higher star line does not mean a longer life. The PE listings show 4.1 and the Outsunny shows 3.6 from 52 ratings, and the lower line tracks a difficult build as much as the plastic.
Heat and the vent
A mesh window is not a roof vent. The VOUNOT lists one mesh vent. The Ohuhu lists two mesh windows. The Outsunny lists one roof vent and rain gutters. The Royal Horticultural Society wants roof ventilation because small houses overheat above about 27°C. On a south wall, a closed PE cover can hold heat you cannot dump except by opening the zip, which also opens the house to wind. A U-value is not claimed for either skin. Polycarbonate is often bought because it feels more rigid and because a panel kit can include a vent. It is not automatically the warmer house in this file, because the file does not measure heat loss.
Gutters matter on a wall. The Outsunny names them. The covers do not, so water off a PE roof can run down the masonry you are leaning on. If the build is the part that worries you, film on both sides and a door rail that reviewers drilled are on how to put up a lean-to greenhouse. The vent is only useful if you will actually open it.
When panels, when a cover
Buy the panels when you will spend the day on a rigid house, you want the roof vent and the gutters, and you can accept 3.6 from 52 ratings and a 62 cm door. That is the Outsunny at £157.69, with the condition that 0.4 cm is the printed thickness and not a 15-year promise. Buy a polythene cover when the job is one season of frost protection, you can stake into soil, and you accept a zip and a skin you may not be able to replace.
The £36.99 VOUNOT is the cheaper of those covers if 180 cm and a shared review file are acceptable. The Ohuhu is the cover to choose when you also want the rack, with the rain pocket as the limit. Who should skip which listing is the best lean-to greenhouse page. If you only have paving, the cover's pegs are the wrong anchor, and the panel kit's ground bolts are the closer match, though they still need a base you can fix. Leave glass, and any EN 12150 toughened-glass specification, outside this choice. They are a different house.
Common questions
Will polycarbonate keep heat in better than a PE cover?
This capture does not measure that. The Outsunny is a rigid panel with one roof vent. The covers are polyethylene with mesh, not a ridge vent. A vent you can open will usually matter more on a hot April day than the name of the plastic. Do not treat a shop U-value for twin-wall as the figure for this 0.4 cm sheet.
How long will 135 g/m² last in a UK winter?
The listing does not say. General notes from Growsave put single-sheet polyethylene at up to about five years, and less without UV stabilisation. That is not a test of the VOUNOT cloth. Reviews in the shared file include both a winter outside and a zip that failed within a week. Plan on a seasonal skin, and check the cover after the first gale.
The Ohuhu page does not state gsm. What do I do?
Do not copy 135 g/m² from the VOUNOT onto it. The Ohuhu file says polyethylene and gives the size, the rack, and the doors. It does not give a cover weight. Judge it on the rack, the 210 cm height, and the review themes, including a cover that started to break up after one season.
Is 0.4 cm the same as 6 mm twin-wall?
No. 0.4 cm is 4 mm, and the Outsunny file does not say the sheet is twin-wall. A 6 mm twin-wall panel is a different product with a different price on specialist sites. Use 0.4 cm as the nominal thickness in this listing, and do not add a light-transmission percentage from another brand's FAQ.
Can I buy a polytunnel sheet to replace the Ohuhu cover?
Unlikely as a direct spare. Horticultural film at 180 or 200 micron is cut for a tunnel, not for this 200 × 100 × 210 cm walk-in with two zip doors. One reviewer could not find a replacement on the listing. A new cover from another brand will not automatically fit the zips or the frame.
Which one has a roof vent?
Only the Outsunny lists a roof vent, and it also lists gutters. The VOUNOT lists one mesh vent. The Ohuhu lists two mesh windows. If dumping heat is the job, the panel kit is the one that names the right part. If you will not open a vent, you have paid for a feature you will not use.
Does a higher star line mean the cover lasts longer?
No. The polyethylene listings show 4.1, including a shared VOUNOT file, and the polycarbonate house shows 3.6 from 52 ratings. The lower score sits next to assembly complaints. The higher score sits next to zip and connector complaints. Stars in this set are not a lifespan test.
Related pages
Sources
Public UK sources named below. amazon.co.uk prices, stars and review counts on these listings were read on 19 October 2026. Page updated 21 October 2026.
- Town and Country Planning (General Permitted Development) (England) Order 2015, Class E (retrieved 2026-10-19)
- GOV.UK permitted development rights for householders, technical guidance (retrieved 2026-10-19)
- Planning Portal outbuildings guide (retrieved 2026-10-19)
- Party Wall etc. Act 1996, section 6 (retrieved 2026-10-19)
- Consumer Rights Act 2015, section 9 (retrieved 2026-10-19)
- RHS ventilation and shading in greenhouses (retrieved 2026-10-19)
- Growsave, alternative greenhouse materials (retrieved 2026-10-19)
- Better Growing Spaces, lean-to greenhouse buying guide (retrieved 2026-10-19)
- amazon.co.uk lean-to greenhouse listings captured 19 October 2026 (retrieved 2026-10-19)