Could bamboo be the next Japanese knotweed?

 Guest article written by Emily Grant at Environet

As awareness of the problems caused by bamboo grows, it’s being flagged up more frequently during property transactions. Emily Grant, Director of invasive plant specialist Environet, explains what surveyors need to watch out for.

Surveyors are well aware of the issues around Japanese knotweed, yet there is no obligation to flag up bamboo on a property survey, despite the fact it can be equally invasive and cause just as much – if not more – damage to property.

There are well over 1,000 varieties of bamboo, but those that fall into the ‘running’ category are the most problematic. Once established, they very quickly send out long, lateral rhizomes that can travel several metres from the parent plant, emerging in new locations – often in neighbouring properties. Bamboo rhizomes are incredibly tough and resilient, easily working their way into building foundations, exploiting joints and weaknesses, as well as drains and pipework, patios and pathways.

We’ve seen several cases of bamboo travelling under buildings and emerging inside. In one particularly memorable case in Hampshire, it had travelled from next door’s garden, penetrated the damp proof membrane of the house and emerged between the skirting board and the wall of the living room. It also made an appearance behind the washing machine in the kitchen and through the study floor. The entire ground floor slab of the house had to be broken up and removed to allow the bamboo rhizome to be excavated, resulting in a home insurance claim exceeding £100,000. This is an extreme case, but it shows how bamboo can easily exploit weaknesses in a property’s structure.

‘Clumping’ varieties tend to remain confined to one area of the garden and are usually much slower to spread, but even they can become invasive over a long period of time.

Impact on property transactions

We are increasingly encountering cases where a surveyor has identified a bamboo infestation and recommended further investigation via a specialist bamboo survey.

As buyers become more aware of the associated risks, and with 8% of UK homes affected by bamboo according to a survey we undertook with YouGov, many are insisting that problematic infestations are addressed prior to purchase – or an appropriate price reduction is applied.

This can cause delays and disagreements between buyers and sellers over who should bear the cost of the survey – and potentially the plant’s removal. It can also lead to transactions falling through where an agreement can’t be reached, or the buyer isn’t prepared to accept the risk of buying the property with the plant in situ.

One of our clients, a first time buyer in Bristol, had noticed bamboo in both the front and back gardens of the terraced house she planned to buy before her surveyor flagged it on his Level 2 report, recommending further investigation. Our team carried out a bamboo survey which determined it was a ‘running’ variety which was already posing a threat to underground pipework and encroaching into the neighbouring property.

The buyer requested a reduction in the price to pay for the bamboo to be removed, but the vendor (supported by their estate agent) refused, stating the work was unnecessary. It was only when they withdrew their offer that the seller finally agreed to a price reduction covering half the removal costs.

Encroachment risks

In addition to the potential damage to their own property and the associated removal and repair costs, buyers and surveyors must also consider the risk of future legal action if the plant has spread or is at risk of spreading to a neighbouring property. One of our clients recounted the shock of answering a knock on the door the day after she moved into her new home, only to be met by her new neighbour asking what she planned to do about the bamboo which had crossed the boundary into their garden. Not the ‘welcome to the neighbourhood’ she might have been hoping for.

Of course, sellers are legally obliged to declare any resolved or ongoing disputes with neighbours, but conflict may not yet have arisen over the issue – or the neighbour may at that point be unaware that the bamboo has already spread beneath the ground into their property.

Other invasive plants

Japanese knotweed remains the most feared invasive plant in the UK due to the associated difficulties selling affected properties and the knotweed ‘stigma’ that continues to impact property values. However, RICS surveys and the TA6 form have proven to be very effective backstops protecting buyers from knotweed risk, forcing sellers to confront the issue by stating whether or not they believe the plant to be present – and providing a route to legal recourse if they fail to carry out proper checks or answer honestly.

There are several other plants that have the potential to damage property, which surveyors should be aware of and be able to identify. Buddleia will grow happily almost anywhere including in walls, chimneys and guttering and can cause cracks in walls, damage to render and damp inside the property. Virginia Creeper grows vigorously using tendrils and disk-like suckers that cling onto structures, blocking air vents, trapping moisture against surfaces and in the worst cases contributing to damp and mould inside. Even ivy, much loved by gardeners across the UK, requires proper maintenance to prevent its adventitious (aerial) roots damaging brickwork, lifting roof tiles, pulling gutters away from walls and blocking light from windows.

However, there’s no doubt that bamboo is the plant most likely to cause serious damage to property or legal repercussions for buyers, without the specific lending restrictions and TA6 question in place to protect them, as with knotweed. They are therefore relying on surveyors as their first line of defence to identify any bamboo issues and flag them up for further investigation.

Environet specialises in expert consultancy as well as the treatment and removal of invasive plants.