Selecting the correct size of polythene cover is crucial for the durability and efficiency of your polytunnel. An appropriately sized cover ensures optimal protection and climate control for your plants. To assist you in determining the exact dimensions required, we’ve developed this comprehensive guide.
Please note
These calculations are based on Northern Polytunnels single span structures – including our EasyBuild Polytunnel – we can’t guarantee the measurements will work on other polytunnel brands.
Understanding Polytunnel Cover Measurements:
To calculate the appropriate size of your polytunnel cover, you’ll need to determine both the width and length of the polythene sheet.
Calculating the Sheet Width:
Measure the Width of Your Polytunnel: Begin by measuring the external width of your polytunnel structure (C).
Consider the Fixing Method: The method used to secure the polythene affects the width required.
Use the table below to determine which roll width you’ll require.
| Width of Polytunnel (C) | Trenching into the ground | Fixing to a base rail | Fixing to a side rail |
| 8ft (2.44m) | Use 9.2m roll width | Use 7.3m roll width | Use 7.3m roll width |
| 10ft (3.05m) | Use 9.2m roll width | Use 7.3m roll width | Use 7.3m roll width |
| 12ft (3.66m) | Use 9.2m roll width | Use 9.2m roll width | Use 7.3m roll width |
| 14ft (4.27m) | Use 9.2m roll width | Use 9.2m roll width | Use 7.3m roll width |
| 18ft (5.49m) | Use 11.1m roll width | Use 11.1m roll width | Use 9.2m roll width |
| 21ft (6.40m) | Use 14m roll width | Use 11.1m roll width | Use 9.2m roll width |
| 24ft (7.32m) | Use 14m roll width | Use 14m roll width | Use 11.1m roll width |
| 27ft (8.23m) | Use 14m roll width | Use 14m roll width | Use 11.1m roll width |
| 30ft (9.14m) | N/A | Use 14m roll width | Use 14m roll width |
Calculating the Sheet Length
Measure the length of your polytunnel (B) and add 6 metres to the total length. This allows 3 metres at either end to accommodate fixing to the door frame.
For instance, for a polytunnel that is 6 metres long, you should order a 12 metre long polythene sheet to allow for proper end fixings.
Now you have the size you require, you can order your polythene here.
