The Knotweed and Mortgage Issues


Japanese Knotweed is listed on schedule 9, part 2 of The Wildlife & Countryside Act 1981, making it an offence under section 14(2)(a) of the Act to ‘plant or otherwise cause it to grow in the wild’. It is an invasive and potentially destructive plant, that in certain conditions has the capacity to cause damage to poorly constructed and very old outbuildings, drains, paths, underground services, cause heave in tarmac or poorly laid concrete surfaces.  

As a consequence of numerous cases having gained nationwide publicity in recent years, the existence of Japanese Knotweed on or close to a property will potentially, have an unfavourable impact on future property sale / purchase and may lead to added unforeseen costs. Unfortunately, there is no one particular solution that will categorically ensure that every lender will endorse a mortgage application. Each UK mortgage lender sets their own policies when assessing applications whereby Knotweed is present on or close to the property for sale. We have personal experience of a mortgage lender declining an application when Knotweed was mentioned in a Homebuyers Report, despite the infestation being on adjacent land in excess of 20 metres away from the boundary and double the distance of any ‘permanent structure’ on the property. Conversely, there are other lenders who have adopted a more relaxed outlook and will lend unconditionally, when Knotweed is growing within a few metres of the foundations. Generally speaking however, the majority of lenders policies would stipulate that at the minimum, a treatment plan (often referred to as a management plan – (click here for more details) be put in place, supplemented by an Insurance Backed Guarantee (IBG), as a precursor to a mortgage application being considered.  


The Risk Assessment of Japanese Knotweed  

(Obtained from RICS Professional Information, UK Japanese Knotweed and residential property 1st edition, information paper IP 27/2012).

The below chart displays the criteria adopted by the Royal Institute of Chartered Surveyors (RICS) to assess the risk associated with Japanese Knotweed on residential property and would come into play as a consequence of a mortgage application being made to any individual lender within the UK. The mortgage lender would instigate a fully accredited chartered surveyor to conduct a Homebuyers Survey Report on the given property and should Knotweed be in existence the foregoing criteria would apply.

This risk assessment takes into account the real risk to a property and addresses some of the concerns of the lenders and insurance companies. The term ‘habitable space’ refers to those parts of the subject property associated with daily living (including conservatories) and not ancillary spaces (such as outbuildings and/or garages).

Any Knotweed graded under category 4 and 3 would evoke tension among the majority of mortgage lenders and in the main, an outright rejection of the mortgage application or at least the requirement of a management plan would be required for an agreement to be reached. Even so, as stated previously, the mortgage lenders implement their own ‘in house’ policies when assessing the risk. Naturally the mortgage lender has the final say and in the event of the mortgage application being unsuccessful (due to the Knotweed) the only remedy is to seek an alternate mortgage lender (unless a ‘cash buyer’ is involved in the transfer!).

The irony is that although Knotweed, just like for example asbestos or damp would be an issue to any property owner, the cases of Knotweed actually reaching a point whereby it causes damage to property are very infrequent, and quite often, the root cause may well be due to poor construction, or not having been clinical in the ground clearing process beforehand. It will however, grow between concrete slabs and can 'penetrate' the cement that bonds bricks/stone in its quest for light and water by exploiting the 'weakest' point. A very subtle difference in terminology yet poles apart in reality. Furthermore, after establishing itself in the soil for a number of years, it can without exception take advantage of pre-existing fractures or weaknesses within a poorly constructed or fragmented old wall for example. It can also cause disruption to underground services (normally very old) and cause 'heave' to thinly laid tarmac. 

"It will grow through concrete" and "until it is gone, you won't be able to sell the house" - That's what we were told in 2009 by representatives of two companies who still operate in South Wales to this day. We even believed it for a while and came close to paying the extortionate fees they required in advance, without any guarantee of success.

We have tried to explain in the foregoing paragraph in simple terms what the plant is capable of. Yet "destabilise/grow through foundations"? You should robustly question any contractor or sales representative who tries to exploit these misconceptions, as they simply aren't true.