These barriers are of a very high specification, and all works are carried out in line with the INNSA Standards, informed by the Environment Agency Code of Practice – Managing Japanese Knotweed on Development Sites.
These products are chosen based on the specification of the works, but are generally one of a small number of similar types of fabric which all must meet rigid performance standards
Where barriers are installed to prevent (re-)infestation from Japanese knotweed, we use a product which is guaranteed for 150 years. This product is also permeable, allowing surface water to drain, but still preventing the plant’s tenacious root system from forcing its way through.
On many occasions, we have seen sites and projects where inferior barriers have been used, and JKSL are called in to remediate the previous owner’s (or contractor’s) mistakes.
Landscaping fabrics may stop ordinary garden weeds from popping up, especially when properly covered, but they won’t stop Japanese knotweed (for long). We often see properties where this type of fabric is laid down over winter after clearing Japanese knotweed surface growth – but it almost always comes back just as strong once the summer is underway.
Unfortunately, this is a tactic frequently used by vendors looking to cover up the presence of Japanese knotweed in order to sell their property – so it’s something to watch out for.
A canny buyer should treat signs of recent landscaping as a warning, checking the adjacent properties. If in any doubt, instructing a specialist survey is the best way to proceed.
Vendors who have had Japanese knotweed remediation works done properly should be able to supply specifications (including for root barriers) for any works done, and they should supply an Insurance-Backed Guarantee for any chemical treatment plan.
Insurance-Backed Guarantees are included as standard by all INNSA Contractor Members for all domestic clients having works carried out on their own home.