Japanese knotweed is an invasive plant species that poses serious risks to properties across the UK. Known for its rapid growth and ability to damage buildings and infrastructure, it is a significant concern for both homeowners and buyers. If knotweed is present on a property, it can reduce its value, cause structural damage, and complicate mortgage approvals.
In this blog post, we will explore the implications of Japanese knotweed on property surveys, how surveyors identify and assess its impact, and what steps you should take if knotweed is found on a property you own or plan to purchase.
What Is Japanese Knotweed?
Japanese knotweed (Fallopia japonica) is a highly invasive plant species that was introduced to the UK in the 19th century. Despite its ornamental appeal, it has since become one of the most destructive plants due to its aggressive root system. Knotweed can grow through cracks in concrete, walls, and other hard surfaces, causing significant structural damage to buildings, patios, driveways, and drains.
The plant spreads rapidly through its rhizomes (underground stems), and even a small fragment left in the soil can cause a new infestation. It’s not illegal to have knotweed on your property, but allowing it to spread to neighbouring land can lead to legal action.
Why Is Japanese Knotweed a Problem for Properties?
The presence of Japanese knotweed can have serious consequences for a property’s structural integrity, its value, and your ability to secure a mortgage. Some of the key risks include:
1. Structural Damage
Japanese knotweed’s rhizomes can grow deep underground and exert pressure on building foundations, walls, and drainage systems. The plant is capable of growing through small cracks in concrete, tarmac, and brickwork, gradually causing significant damage over time. This can lead to costly repairs and pose safety concerns.
2. Property Devaluation
Due to its reputation for causing damage, the presence of Japanese knotweed can significantly reduce a property’s value. Homeowners may find it difficult to sell a property with knotweed, and potential buyers may be hesitant to invest in a home with an infestation.
3. Difficulty Obtaining Mortgages
Mortgage lenders are often reluctant to approve loans for properties with Japanese knotweed, as it represents a risk to the building’s structural integrity. However, some lenders may approve a mortgage if a management plan is in place to control and eradicate the plant.
How Surveyors Assess Japanese Knotweed
If you’re buying a property, particularly an older home or one located near waterways or railways (common areas for knotweed growth), it’s important to have a qualified surveyor inspect the property for signs of knotweed.
1. Identifying Japanese Knotweed
Surveyors are trained to identify Japanese knotweed by its distinct characteristics:
- Heart-shaped or shield-shaped leaves: Knotweed has green leaves that grow in a zigzag pattern along the stem.
- Hollow stems: Its bamboo-like stems are hollow, often growing to over 2 meters in height during the summer.
- White flower clusters: During late summer, the plant produces small, white flower clusters.
- Deep root system: The rhizomes can spread several meters underground, even if the plant is not immediately visible above ground.
Surveyors will also check for any signs of structural damage caused by knotweed, such as cracks in foundations or paths, or bulging walls.
2. Assessing the Risk
When a surveyor identifies knotweed on a property, they will assess the extent of the infestation and the potential risk it poses to the building. This assessment will typically be categorized based on the RICS Japanese Knotweed Risk Categories, which range from Category 1 (knotweed more than 7 meters away from the building and unlikely to cause damage) to Category 4 (knotweed within 7 meters of the building, with significant damage already observed).
3. Including Knotweed in the Survey Report
If knotweed is found on or near a property, the surveyor will include details of the infestation in the Homebuyers Survey (Level 2) or Building Survey (Level 3) report. The survey will outline the risks, potential damage, and any recommended actions, such as hiring a specialist to remove or control the plant.
What to Do If Japanese Knotweed Is Found on Your Property
If a survey reveals the presence of Japanese knotweed, don’t panic. While knotweed can be challenging to manage, there are steps you can take to control and eventually eradicate the plant:
1. Hire a Specialist
The most effective way to deal with knotweed is to hire a professional knotweed removal company. These specialists are experienced in handling knotweed infestations and will put a management plan in place. Treatment options include herbicide application, excavation, or root barrier installation.
2. Implement a Knotweed Management Plan
If you’re planning to sell a property affected by knotweed, mortgage lenders will likely require a formal knotweed management plan. This plan should be put in place by a specialist company and should include:
- A detailed assessment of the infestation.
- A timeline for herbicide treatment or removal.
- A guarantee (usually 5 to 10 years) to ensure the knotweed does not return.
3. Prevent Spread
It’s important to ensure that knotweed doesn’t spread to neighbouring properties, as you could face legal action if the plant causes damage elsewhere. Regularly monitoring and maintaining the knotweed on your property can prevent it from spreading and causing further issues.
The Impact on Property Value and Sales
While the presence of Japanese knotweed can be a concern for homeowners and buyers, it doesn’t necessarily mean that a sale will fall through. Many properties with knotweed infestations are still sold successfully, especially if there is a management plan in place. However, you may need to adjust your expectations for the property’s value or take additional steps to reassure potential buyers.
1. Selling a Property with Knotweed
If you’re selling a property with knotweed, it’s important to be upfront with potential buyers about the issue. Having a professional knotweed survey and management plan in place can help reassure buyers and lenders that the problem is being handled.
2. Buying a Property with Knotweed
If you’re buying a property that has knotweed, you’ll want to ensure that there is a management plan in place or be prepared to arrange for the plant’s removal yourself. Be sure to discuss the issue with your mortgage lender, as they may have specific requirements before approving the loan.
How Lyman Marshall Chartered Surveyors Can Help
At Lyman Marshall Chartered Surveyors, we understand the serious implications of Japanese knotweed on properties. Our RICS-certified surveyors are trained to identify knotweed during property surveys and provide expert advice on how to manage the situation.
Whether you’re buying, selling, or simply concerned about the impact of knotweed on your property, we can provide detailed surveys that highlight the risks and offer guidance on the best course of action.
Conclusion
Japanese knotweed is a serious concern for property owners and buyers due to its ability to cause structural damage and reduce property values. However, with the help of professional surveyors and knotweed removal specialists, it’s possible to manage and eventually eliminate the problem.
If you suspect Japanese knotweed is present on your property or are purchasing a home where it may be an issue, contact Lyman Marshall Chartered Surveyors today to arrange a comprehensive survey and ensure you’re taking the right steps to protect your investment.
