What are the RICS Updated Guidelines for Japanese Knotweed Treatment

japanese knotweed in summer

Japanese knotweed (Reynoutria japonica) is an invasive, fast-growing weed that can cause damage to structures and property. It grows extremely quickly, penetrating cracks and joints as it spreads. Japanese knotweed can grow to depths of two metres and extend up to seven metres horizontally from the visible part of the plant.

It can also cause damage to buildings that are within seven metres of the above-ground portions of the plant. Plus, it can impact native plants in your garden by releasing chemicals that suppress plant growth and germination. Therefore, it is important to control its spread at the right time.

News RICS Guidelines for Japanese Knotweed Treatment

The Royal Institution of Chartered Surveyors (RICS) implemented an updated guidance note on Japanese knotweed in 2022. The RICS Management Category Assessment for Japanese knotweed now uses a decision tree to categorise infestations into four categories: A, B, C, and D, instead of the earlier RICS Risk Category.

These new management categories will help you assess how, sooner rather than later, you will need a Japanese Knotweed Treatment.

Management Category D

Management Category D applies when Japanese knotweed is off-site but within 3 metres of a property’s boundary. In this category, a specialist remediation contractor should advise on possible encroachment and appropriate management. Lending advice in this category is no mortgage retention except in exceptional circumstances.

A remediation specialist would only be brought in if there was a need for defensive action against neighbouring properties or to help instigate legal action against neighbouring properties.

Management Category C

Management Category C is considered “low impact” by the RICS. In this category, there’s no mortgage retention recommendation. The RICS recommends that the client seek specialist advice. In Management Category C, the knotweed is present but not causing damage or affecting amenity. The impact on value is lower because structures and amenity spaces have not been affected. Remedial costs are at the owner’s discretion.

A private homeowner may still want to seek help from a specialist company.

Management Category B

Management Category B is applied when Japanese knotweed is visible on-site, there is no visible damage to structures, and Japanese knotweed is likely to prevent use of or restrict access to amenity space. In this category, remediation from a specialist company is required, and an insurance-backed guarantee must cover work.

The cost of remediation will be related more directly to the value of the property because no structural repairs will be needed.

Management Category A

Management Category A is the most severe category. It applies when Japanese knotweed is on-site; it’s causing visible material damage to a significant structure; it’s within 3m of a habitable space; it’s likely to affect the value of the property because repair and remediation costs will be incurred. In this category, mortgage retention is advised pending a report from a specialist that highlights the appropriate action required. Lending advice is no mortgage until a specialist report is obtained and a suitable remedial plan is agreed upon.

Non-lending advice is to have a specialist remediation contractor advise appropriate action.

The RICS management categories for Japanese Knotweed Treatment provide a clear framework for assessing the severity of an infestation and determining whether a specialist contractor is needed. If you have Japanese knotweed on your property, it is important to have it assessed by a qualified professional to determine the best Japanese Knotweed Treatment for your needs.

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