How To Build A Polytunnel

Once you decide to invest in a polytunnel, you want to be sure you are buying a quality product that is value for money. We always recommend purchasing the best quality product your budget will allow. That way, you are sure to get years of service instead of forking out for repeat repairs. If you are on a tight budget, one way to save money is to install your own polytunnel. Even if you are not a DIY master, you should be able to tackle a basic garden polytunnel.

Although polytunnels constructions are not complicated structures, there's a bit more to it than building a tent. With the help of a friend, you should be able to install your polytunnel over the course of a weekend. Of course, this is a rough guide, and the weather, the ground, tunnel size and your DIY skills will all affect the time it takes. One piece of advice. If the weather is looking windy, don't attempt to build or cover your polytunnel!

Building a Polytunnel

Since their first introduction to the gardening world, not much has changed in the basic design of a polytunnel. Although materials have improved, their construction remains the same.

A standard polytunnel comprises of a steel frame. The frame is a series of hoop sections that are spaced at regular intervals and held in place by stabilisers and a central ridge. Standard practice is to place the polytunnel directly onto the earth so that you can plant straight into the soil. The polytunnel is secured in place by foundation tubes. The tubes are driven into the ground and prevent the structure from blowing away. There is no need for a solid foundation like a greenhouse. However, you can still build a polytunnel on a slab if you wish. Instead of foundation tubes, base plates are used to secure the polytunnel to the slab. 

Once you connect the framework and secure it in place, you are ready to attach the poly cover. 

Covering a Polytunnel

When covering a polytunnel, one of the most important things is to get the polythene cover as taught as possible. A taught surface copes better with rain and snow. You want the water to run off, not collect in the middle of the roof space!  

There are a couple of different methods to get your cover taught. For most domestic or commercial tunnels you dig a trench around the frame of the polytunnel. The edge of the polythene cover is placed in the channel and backfilled with dirt. 

The alternative method is to fit timber or aluminium base rails to the polytunnel frame at ground level. You attached the polythene cover to the base rails and hold it in place with timber battens and nails or PVC infills. The advantage of base rails is you can easily adjust the tension once the cover is in place, unlike the trench method. 

Once your polytunnel cover is in place, it is time to add the doors. We recommend a timber frame door at either end of the polytunnel for access and ventilation. It is a more robust and accessible solution than roll-up or zip doors. A door opening inward will take up extra room but will be less prone to wind damage when you leave it open. Another option is a sliding door or doors, but this does add extra cost.