Home Selling Knotweed is knocking £34.12bn off of UK property values

Knotweed is knocking £34.12bn off of UK property values


Moving Home Advice has looked at the value being wiped from UK house prices due to the nation’s growing knotweed epidemic and what this equates to for the average homeowner in different areas across the UK. 

In just two months the Japanese housing horror will start to rear its ugly head again and by June it will have grown to over three metres. 

It’s believed that at least five percent of homes across the UK are affected by knotweed, knocking 10%, or £23,530, of the average UK property’s value. With 29 million homes across the nation, that’s 1,450,000 properties impacted with a huge £34.12bn wiped off in value. 

The cost of dealing with knotweed is hefty and can run into tens of thousands of pounds for even a modest size garden, taking as long as five years to treat fully. 

All the while, the average UK homeowner will see the value of their home slump by £23,530, this is, of course, higher in London (£47,546), the South East (£32,664), the East of England (£29,128) and the South West (£25,976).

With the highest house prices in the land, homeowners in Kensington and Chelsea stand to lose £119,162 on the price of their property if they find it has been infested with knotweed. 

Westminster and Camden are the next largest price losses, facing a loss £93,860 and £86,280 respectively, while South Bucks is the home to the largest loss outside of London at £59,792, followed by Elmbridge (£59,673) and Chiltern (£54,617). 

According to the Japanese Knotweed Removal specialists, Environet UK, it costs the average homeowner £2,500 to treat Japanese knotweed with herbicide and £5,000 upwards to excavate it. Environet has a handy treatment cost calculator on its website which takes into account the size of the visible infestation.

But if you don’t want to pay up, you ignore Japanese knotweed at your peril. Not only will you be putting your property at risk of damage, but you’ll also be liable if the plant spreads to a neighbouring property and you won’t be able to sell up either.

The plant is easier to deal with before it becomes well established, so leaving it to grow and spread will only lead to bigger problems later on. Knotweed that is ignored for years can pose a threat to property, growing through cracks in concrete, patios, asphalt, cavity walls, gutters and drains. It can exploit cracks in brickwork, eventually forcing walls to break apart.

 Mortgage lenders now require the sellers of properties affected by knotweed to provide evidence of a professional treatment plan along with an insurance-backed guarantee for the work, before they will offer a loan. Sellers are also required by law to tell buyers if a property is or has been affected by Japanese knotweed, as a specific question now forms part of the TA6 conveyancing form.

Knotweed is a homeowner’s worst nightmare and there really is no DIY fix for this aggressive backyard vandal. It can take months on end to ensure it has been properly disposed of but can be more costly should you decide to turn a blind eye. 

The quicker you can get on top of the problem the better as a house with a knotweed problem will not only drop in value but will also struggle to find a buyer.

Nic Seal, Founder and Managing Director of Japanese knotweed removal firm Environet UK, commented:

“Although knotweed is causing havoc around the world, Britain leads the way in tackling the spread of the highly invasive weed. There are two main ways to treat it. The traditional herbicide method can be carried out between April and October, because it requires the plant to be in leaf, therefore it usually takes two or three growing seasons – or years – to complete.

Growing in popularity amongst homeowners, and offering a much greater degree of certainty, is the excavation of the entire plant. This can be done in a matter of days, at any time of year, using a mini-digger to remove the rhizome from the ground where every viable piece is separated from the soil. Our Resi-Dig-Out™ method is the most environmentally friendly solution as it requires no chemicals and allows the clean soil to be returned to the ground, so eliminates the need for landfill disposal too.

Those who attempt to deal with the Japanese knotweed themselves, by cutting it down repeatedly, pouring diesel on it, covering it in salt, burning it, burying it and saturating it in over-the-counter weed killers, will find those methods categorically don’t work. Japanese knotweed can lie dormant for up to twenty years only to strike again when you least expect it – and in fact some DIY methods can induce dormancy, making the infestation more difficult to treat by professionals.”

UK – 2019 – overall impact of knotweed
Existing homes – approx 29 million homes
Average UK House Price £235,298
Knotweed impact 10%
Knotweed impact value £23,530 (Nov 2019 ave hp)
5 per cent of UK houses are currently affected by knotweed either directly or indirectly
UK number of homes = 29,000,000
5 per cent affected = 1,450,000
Number of affected homes = 1,450,000
Knotweed impact value (on UK ave hp) = £23,530
Total impact in £ value terms = £34,118,258,466
Largest price impact from Knotweed of all UK areas
Location Current Average House Price Impact on value House Price Afterwards
Kensington And Chelsea £1,191,616 £119,162 £1,072,454
City of Westminster £938,596 £93,860 £844,737
Camden £862,799 £86,280 £776,519
Hammersmith and Fulham £731,044 £73,104 £657,940
City of London £709,998 £71,000 £638,998
Richmond upon Thames £665,390 £66,539 £598,851
Islington £627,907 £62,791 £565,116
Wandsworth £599,334 £59,933 £539,401
South Bucks £597,924 £59,792 £538,132
Elmbridge £596,727 £59,673 £537,055
Haringey £569,364 £56,936 £512,427
Hackney £565,018 £56,502 £508,517
Chiltern £546,167 £54,617 £491,550
Three Rivers £529,439 £52,944 £476,495
Barnet £525,458 £52,546 £472,913
East Midlands £197,792 £19,779 £178,013
East of England £291,281 £29,128 £262,153
London £475,458 £47,546 £427,913
North East £130,712 £13,071 £117,641
North West £169,362 £16,936 £152,425
South East £326,636 £32,664 £293,973
South West £259,758 £25,976 £233,782
West Midlands Region £204,238 £20,424 £183,814
Yorkshire and The Humber £165,642 £16,564 £149,078
England £251,222 £25,122 £226,100
Wales £172,574 £17,257 £155,316
Scotland £154,798 £15,480 £139,319
Northern Ireland £139,951 £13,995 £125,955
United Kingdom £235,298 £23,530 £211,769

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