So what is a root barrier? Well in terms of Japanese knotweed, the Environment Agency make a number of specific recommendations, these are:

It must be capable of being used without damage to the root barrier
It must be provided in large sizes, to minimise the need for seals
It must be sealed securely
It must have the physical properties to remain intact for 50 years
If exposed to sunlight, it must be able to resist UV damage
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