Bamboo and Japanese Knotweed - Encroachment Can Damage Property Value

When it comes to invasive plants, most homeowners are aware of the risks associated with Japanese Knotweed. However, bamboo (often seen as an innocuous garden plant) can cause equally serious damage to properties and their market value.

If bamboo or Japanese Knotweed is spreading from a neighbouring property, you could have a legal claim. At Taylor Rose, we help property owners take action against invasive plant encroachments to protect their homes and investments.

How Japanese Knotweed and Bamboo Affect Property Values

Japanese Knotweed is notorious for reducing property values, sometimes by up to 15%. Mortgage lenders often refuse to lend on properties affected by Knotweed without a professional treatment plan.

Bamboo, particularly running varieties like Phyllostachys aurea, can cause similar problems. Its underground rhizomes can damage structures and spread rapidly onto neighbouring properties. Although bamboo is not currently listed as a controlled species under the Wildlife and Countryside Act 1981, it can still pose serious legal and financial risks.

Mortgage lenders appear to be becoming increasingly cautious, and the stigma attached to properties affected by invasive plants can lead to significant diminution in value.

Case Study: Bamboo Encroachment at a Residential Property

We recently acted for a homeowner whose property was impacted by bamboo encroachment from a neighbouring garden.

Our client’s home was found to have significant bamboo invasion across the boundary, and we therefore instructed an independent RICS Registered Valuer to assess the impact on market value. We instructed the surveyor to attend the property and review a report our client had already procured from Environet and produce a CPR compliant report. The results of the report meant that the value of our client’s claim significantly increased which provided significant leverage in resolving this dispute.

Expert Methodology: How Diminution of Value Was Assessed

The expert applied a structured valuation methodology, using principles established for Japanese Knotweed cases and adapted them to bamboo. The steps included:

1. Establish Unaffected Market Value

The property was valued at £200,000, assuming no bamboo encroachment.

2. Assess Costs Associated with Bamboo Removal

Professional removal and installation of a root barrier: £7,500 including VAT.

3. Allow for Repair Costs

Reinstatement of disturbed paving and structures: £2,000.

4. Account for Disturbance and Inconvenience

A further £500 allowed for the disruption caused by excavation and treatment works.

5. Apply a Stigma/Disclosure Discount

A 2% reduction (£4,000) applied to reflect ongoing stigma, disclosure obligations at resale, and lingering buyer concerns.

6. Calculate Total Diminution

The total loss was assessed at £14,000, reducing the market value from £200,000 to £186,000.

Why This Methodology Matters

Whilst there is currently no specific RICS guidance for bamboo-related valuations, the structured approach used in Japanese Knotweed cases is well-established and was deemed appropriate.

The expert's opinion considered:

• The absence of formal RICS guidance but similarities to Knotweed cases

• Market perception risks, not just physical damage

• Legal disclosure obligations even though bamboo is not yet a statutory plant

• The impact of future media coverage and public awareness

This comprehensive and logical methodology ensures claimants can robustly evidence their losses which is an essential element of any legal action.