How to fit polytunnel polythene without early tears
Updated: October 2026
You have the sheet, the frame is ready and the weekend forecast looks usable. Learning how to fit polytunnel polythene is mainly about controlling wind, removing sharp contact points and applying even tension so the cover cannot flap. The [greenhouse film comparison](/hub/raised-beds-greenhouses-and-compost/greenhouse-film) helps if you still need a sheet; this guide assumes the piece already spans your frame. It follows UK tunnel-makers’ fitting advice and uses two failures from the comparison as warnings: a sheet cut by cable ties and another ripped when used as a temporary roof.
You have the sheet, the frame is ready and the weekend forecast looks usable.
You have the sheet, the frame is ready and the weekend forecast looks usable. Learning how to fit polytunnel polythene is mainly about controlling wind, removing sharp contact points and applying even tension so the cover cannot flap. The greenhouse film comparison helps if you still need a sheet; this guide assumes the piece already spans your frame. It follows UK tunnel-makers’ fitting advice and uses two failures from the comparison as warnings: a sheet cut by cable ties and another ripped when used as a temporary roof.
Our top picks
| Badge | Product | Cut to size | Anti-drip claim | Stated size | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  GSHUR GSHUR 2 m × 2 m polythene sheet | – | No | 2 m × 2 m | 7.8 | about £7.99 | View offer |
 AGGAFA AGGAFA 150 µm greenhouse film, 2 m × 3 m | Yes | No | 2 m × 3 m | 8.6 | about £12.99 | View offer | |
 Pumtus Pumtus 6 mil greenhouse film, 3 m × 8 m | Yes | Yes | 3 m × 8 m | 6.8 | about £16.14 | View offer |
On this page
Choose the day and the people
Do not start while the film is moving in your hands. Northern Polytunnels advises covering in winds below 15 mph, while First Tunnels recommends a still day and at least two people for a full tunnel. If you cannot hold the loose film without fighting it, wait.
A walking tunnel needs helpers who can lift and centre the film without dragging it. Never walk on the film because grit beneath a shoe can puncture it.
Prepare every contact point on the frame
Run a gloved hand around the structure before opening the sheet. Look for burrs, screw ends, splintered timber, rough joints and old wire. Smooth or cover each point that could rub through moving plastic.
The one UK Pumtus review says the plastic was cut where it passed over cut cable ties. Do not let film bear directly on trimmed ties; reposition or replace them and cover the contact point.
None of the eight compared sheets lists wiggle wire, channel or clips in its included-components line. Buying a piece of film therefore does not buy a complete fitting system. Measure once more after preparing the frame. The relevant dimension is the route over the hoops and into the fixings, not simply the ground width. If your sheet does not provide enough material for that route and the ends, stop before cutting. The polytunnel sizing guide covers that decision separately.
Put the correct face inside and tension evenly
Some horticultural films have a functional inner face. Northern advises fitting printed film with the writing facing inward; this identifies the intended orientation for its product. If a manufacturer states which side carries an anti-drip treatment, follow that instruction. Do not transfer Northern’s rule automatically to an unprinted amazon sheet whose listing merely uses the word “anti-dripping”.
Centre the film before applying final tension. Secure one reference edge according to the frame system, keep the sheet square, then work in an orderly sequence rather than fully tightening one random corner. Northern describes installing wiggle wire from the lintel downwards before tensioning across the hoops.
The finished skin should be taut enough not to flap, without being stretched so aggressively that the film thins or the fixing points take all the load.
Handle folds, small frames and temporary roofs
Several sheets in the comparison arrive folded rather than on a roll. GSHUR reviewers mention pronounced creases, and AGGAFA reviews also discuss folded film. Lay the sheet out on a clean, smooth surface before fitting and give the folds time to relax.
If a crease forms a white stress line, crack or puncture, treat that as damage rather than trying to stretch it away.
The GSHUR raw file contains a warning about using general-purpose polythene as a roof: one UK buyer says it ripped in the first storm. A dust sheet without stated gauge, UV term or designed fixings is not turned into a storm-resistant roof by adding more ties.
Check the cover after fitting
Inspect the tunnel from inside and outside before leaving it. Look for flapping bays, film resting on sharp hardware, distorted clips and water pockets. Re-tension only through the intended fixing system; do not puncture a sound sheet to cure slack.
Ventilation remains necessary. The Royal Horticultural Society advises ventilation and shading to manage greenhouse heat. Keep vents, doors or roll-up sides usable.
If fitting reveals that the parcel is not the listed size, return to the comparison rather than patching several pieces into a larger skin. And if you are deciding between plain film and a sheet with eyelets and rope, read greenhouse film or clear tarpaulin before changing the fixing method.
Common questions
Do I have to wait for a hot day?
No. A warm day makes polythene more flexible, but calm conditions matter more. Northern advises winds below 15 mph and First Tunnels recommends a still day. Postpone if the loose cover is acting like a sail, regardless of temperature.
Which way round does anti-drip film go?
Follow the named film manufacturer’s instruction. Northern says its printed film goes with the writing inward. If an unprinted listing says only “anti-dripping” and gives no face instruction, do not guess that one side has a specific treatment; ask the seller.
What holds the edge if the box has no wiggle wire?
The eight compared sheets do not list fixings, so you need the system designed for your frame. A tunnel may use channel and wiggle wire, while a cold frame may use suitable clips or battens. Avoid puncturing the film or relying on exposed cable-tie ends.
How tight should the cover be?
It should be evenly taut so it does not flap, without visibly stretching at individual fixings. Centre it first and adjust in sequence. Local white lines, sharp wrinkles or distorted clips indicate a snag or concentrated load rather than useful tension.
What if the sheet arrives folded and creased?
Unfold it on a clean surface and let it relax before fitting. Gentle ambient warmth may help. Do not use flame or concentrated heat, and do not pull one corner excessively in an attempt to remove a shipping crease.
Related pages
Sources
Public UK and manufacturer sources from the research digest, used for this page in October 2026.
- BSI — BS EN 13206:2025 greenhouse and tunnel films (retrieved 17.10.2026)
- Northern Polytunnels — Durathermic clear polythene (retrieved 17.10.2026)
- Premier Polytunnels — polythene films (retrieved 17.10.2026)
- Northern Polytunnels — covering a polytunnel (retrieved 17.10.2026)
- RHS — choosing a greenhouse (retrieved 17.10.2026)
- Consumer Rights Act 2015, section 11 (retrieved 17.10.2026)
- GOV.UK — waste duty of care code of practice (retrieved 17.10.2026)
- SEPA — agricultural waste (retrieved 17.10.2026)