How to Erect Your Polytunnel Greenhouse

How To Construct Your Polytunnel & Polycarbonate Greenhouse


A polytunnel provides an ideal opportunity to extend the growing season and to grow your produce all year round.

By providing an enclosed space gardeners and food growers can take advantage of the warmer temperatures a polytunnel offers as well as the protection from the worst of the elements it provides. 

Selecting Your Polytunnel Site

Polytunnels come in all shapes and sizes, allowing you to find the right one for your garden or allotment space. You will want to ensure the site where you erect the polytunnel is level and fairly well protected from the wind if possible.

Look to have one side of the polytunnel facing the direction of the prevailing wind rather than having this gusting in through the doors. It is also best to avoid locating a polytunnel beneath or too close to trees to avoid damage from falling branches.

Finally, make sure there is at least a one meter space all around the perimeter of the tunnel’s ‘footprint’ to give you manoeuvring room to make its construction easier.

Before You Begin

In the flush of excitement on delivery of your brand new polytunnel there is the urge to crack on and get it built. However, take a deep breath and first make sure all the pieces which should be included are included.

Lay out all the kit and tick each item off against the manufacturer’s list of contents. Take a little time to look through the accompanying construction instructions to familiarise yourself with the process.

Regardless of prior DIY experience follow these instructions through the process to try and prevent any unnecessary mishaps. Then wait for a pleasant, warm day to construct your polytunnel.

As well as making the plastic covering more pliable and easier to fit, you will be more likely to take your time when the weather is favourable and less likely to try and rush the job through.


Although polytunnels can manage with a slight slope it is best to level off the ground as much as possible. If you are planning to grow plants directly in to the soil rather than in containers it can also be best to prepare the plot prior to constructing the tunnel.

Although the construction of polytunnels follow the same basic methods, check with the manufacturer’s instructions to see if any additional groundwork is required such as a trench around the perimeter to bury the cover to keep it tight.

For accuracy’s sake use the 3,4,5 triangle method of measurement to work out the position of the framework’s ground tubing before beginning the construction.

Erecting the Frame

To put up the frame closely follow the manufacturer's instructions. Most polytunnels will require tubes to be driven in to the ground to provide stability. Generally it is best to start by erecting the horizontal elements of the frame before applying the upper parts and door frames. Provided you follow the instructions this should not be too difficult a task.

Applying the Plastic Cover and Doors

This is the part of the job where you will be better off having at least one additional work-mate to help. Best done on a wind-free day, stretch the covering across the frame and attach it at the base of the polytunnel as per the manufacturer's instructions.

The plastic cover needs to be tight without any gaps where the wind can penetrate and potentially relocate your newly acquired polytunnel elsewhere in the neighbourhood.

For this reason ensure you have enough time to complete the job in one go. On the same day you apply the plastic cover you should also fit the polytunnel doors.