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How to choose your Thickness of Polythene

Polythene Thickness (Thicker isn't always better!)

Polytunnel Polythene comes in a range of thicknesses, i.e....
600 gauge / 150 micron
720 gauge / 180 micron
800 gauge / 200 micron 

From a manufacturing perspective Polytunnel Polythene could be made as thick as say a Damp Proof Membrane Polythene which would be 1200 gauge / 300 micron.  The reason this is not done is simply because the thicker the polythene the more difficulty the light has getting through, which obviously does not create the best growing environment.

Thick 'numb' polythene would also be very difficult to stretch over a polytunnel to get the 'drum tight' fit that is so important to the long life of the polythene. Polytunnel covers fitted loosely endure repeated movement caused by the forces from the weather, which can subsequently cause damage, polythene that  is tightly stretched over your polytunnel will have minimal movement and will therefore be less likely to be subject to mechanical damage from movement (remember your guarantee on the polythene is a UV stabilisation guarantee - not a guarantee against damage caused by badly fitted polythene).

720 gauge /180 micron has become a 'happy medium' in polytunnel polythene thickness.  It has to also be remembered that the 'thickness' of polythene does not relate to how strong the polythene is.  Due to additives such as metalocene, polytunnel polythene of all thicknesses are as strong as each other in respect of Break Points and Tear Strengths.

It is also worth remembering that thicker doesn't mean a longer lifespan.  It is the UV stabilsers that are added to the polythene during manufacture, that gives the polythene its long life.  If you took a piece of very thick Damp Proof Membrane Polythene (1200 gauge / 300 micron) and left it outside in the sunshine, it would only last about 6 months !  All our polytunnel polythene is of course UV stabilsed with a lifespan UV guarantee of 5 years, although its expected lifespan is in excess of 8 years. Some of our long term customers have reported lifespans of 10 or more years.

To sum up - it is not as simple as thicker is better!

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