Using Polycarbonate sheets

Our problem greenhouse

Greenhouse with missing glass panelsCredit: Andrew Green, 2011We have spent the last eight months restoring an abandoned allotment we took over. Our most recent  task, having cleared and prepared the ground and erected a shed for our tools, was to repair the greenhouse we inherited with the site.

Now replacing greenhouse glass might be the simplest of tasks for some people but I am a do it yourself dunce. My wife is better than me:  most people are, but she isn't an expert either. Fortunately a neighbour on the allotment came to our aid by suggesting we replace the greenhouse glass using 4mm polycarbonate sheets.  The site had been vandalised and the shed that once stood there had been burned to the ground so you can imagine that the greenhouse was not in a good state. The basic structure was there but half of the greenhouse glass was missing. We had removed the dangerous and broken glass before turning our attention to other things; but now, with the hard work of preparing the ground behind us , it was time to think about planting and we needed somewhere to bring seeds and tender plants on. It was time to repair the greenhouse.

Polycarbonate sheets

Cross section of polycarbonate sheetCredit: amazon

Polycarbonates are a form of thermoplastic polymer. Thermoplastics are a group of polymers that turn to a liquid when heated and cool to a glassy state when cooled sufficiently. they can be easily worked and shaped to create a range of products including polycarbonate sheets. The glass like properties of Polycarbon are retained up to about 150C and it turns to liquid at about 300C.  So there is no fear of it melting in an English summer! The use of polycarbonates for garden buildings like the greenhouse is fast becoming the norm.  Polycarbonates for greenhouse use are given a special surface treatment to make them scratch resistant.

 Where to buy polycarbonate sheets

For greenhouse use you need 4mm polycarbonate sheets. You need to measure your greenhouse but polycarbonate sheets come in standard sizes for greenhouse use so you should not have a problem. We found a range of suppliers and everything we needed on the Amazon site. 

In addition to the polycarbonate sheeting you will need galvanized wire glazing clips, 25mm aluminium foil tape and, depending how your greenhouse is constructed a set of overlap (or 'z') clips.

Cutting the polycarbonate sheets to size. 

This was the eye opener for me. This stuff is so easy to work with. Much easier to cut than glass and you don't risk cutting yourself. Unless you are careless with the Stanley knife of course but I would always recommend you take care there.

Our 4mm polycarbonate came in 8ft x 2ft sheets so, where we had big gaps it didn't need cutting at all or only needed a trim. But the bits that did need cutting were really easy we shouldn't have worried about it.

Someone recommended we use a pad saw to cut through the sheeting. It took a bit of searching to find one but when it came to it we found it wasn't really needed.  We could cut through the polycarbonate sheets with a combination of a Stanley knife and a good pair of scissors.

Measure up the sheet that needs to be cut to size. It comes with a plastic film on so you can mark the outside with the line where you need to make a cut. Score a line with the Stanley knife  using a straight edge. A steel rule would be ideal. We didn't have one and had to make do with a straight piece of wood. If you have cut deep enough you should be able to bend back the polycarbonate sheet along the line of your cut. It is then an easy matter to cut and trim the sheeting to the size and shape you want.

Fixing the polycarbonate sheets to your greenhouse

How the wire clips sitCredit: Andrew Green 2012

First take your 25mm aluminium tape and apply it to the metal frame of the greenhouse. This helps keep moisture out and makes it a tight fit.

Next you will need galvanised wire clips. These are less complicated than they look.  The straight bits sits behind the glass. The two prongs then clip behind the greenhouse frame. I have attached a picture to show how this looks.

The overlap clips are for use where two sheets need to overlap. These are simple and straight forward.

We got everything in place sooner than we expected and now have a fully functioning greenhouse. If we can do it as non DIY types I'm sure that you could too.