Home insurance for properties with Japanese knotweed

Find out what your legal responsibilities are when it comes to Japanese knotweed, how to get rid of it and whether it affects your home insurance

amy smith
Amy Smith
Updated 07 December 2019   | 3 min read

What is Japanese knotweed?

Japanese knotweed is a non-native, invasive plant that can grows extremely fast, reaching up to 3 metres tall with roots that spread for metres in all directions.

It won’t be stopped by tarmac and can spread from even the smallest piece of root left in the ground, making it a risky plant to have near your home.

Key points

  • Most home insurance policies don’t cover knotweed damage or removal.
  • Having knotweed on your property shouldn’t affect the price of your home insurance as it’s not included in the cover.
  • Japanese knotweed is notoriously tricky to get rid of. It can grow back from a tiny piece of root and can take years to kill with chemicals.

How does it affect home insurance?

If not properly maintained or removed, knotweed can cause subsidence and structural damage to your property.

However, most home insurance policies don’t cover knotweed damage or removal, so you won’t be able to make a claim.

On the bright side, having knotweed on your property shouldn’t affect the price of your home insurance as it’s not included in the cover. We don’t ask you about it during our quote process.

Your legal responsibility

It’s perfectly legal to grow knotweed on your premises. However, there are some rules you need to abide by:

  • The weed can’t grow onto or damage another persons’ property
  • If you sell your house, you must declare if there is Japanese knotweed growing on your property by filling out a property information form (TA6). You’ll also need to include an eradication plan, set out by a professional company.

Disposal of the weed is strictly controlled, too. You could face a fine up to £5,000 and up to 2 years in prison if you don’t dispose of it correctly. You can view the full rules on the website.

How to spot Japanese knotweed

There are certain characteristics that make it easy to identify Japanese knotweed. Look for:

  • Shield-shaped, 10 to 15cm green leaves with a flat base
  • Zig zagging, purple-speckled stems
  • Rhizome crown at base of plant with white shoots

The weed dies back during the winter and begins to grow again during the spring. Here’s how to spot Japanese knotweed throughout the year:

Spring: Purple shoots emerge from the ground, eventually forming thick canes

Summer: The canes develop purple flecks. By late summer they sprout spiky clusters of off-white flowers

Autumn and winter: The flowers die off leaving dead, hollow brown bamboo-like canes

How to get rid of Japanese knotweed

Japanese knotweed is notoriously tricky to get rid of. It can grow back from a tiny piece of root and can take years to kill with chemicals.

Hire professionals

The best way to get rid of knotweed is to hire a company that specialises in removing it.

Doing this could get expensive though, so this might be an option when you have a large amount of persistent knotweed.

Make sure any professionals you hire are registered waste carriers, so you'll know the knotweed will be disposed of correctly.

Chemical control

It’s possible to get chemicals to spray on the plants to help prevent them spreading.

This can take up to 3 years to render the plant dormant, making it extremely time consuming.

Professional contractors will have access to more powerful chemicals which could speed up the process. Weigh up the cost of the treatment against the inconvenience of doing it yourself.

Burn it

It’s possible to dig up the knotweed and burn it yourself.

You'll need to make sure to dig up all the weed, or it could continue growing from the left-over root. You also need to wait until the weed is dry before you can burn it, and you may only do so in line with your local bylaws.

Businesses wanting to burn Japanese knotweed will need to tell the Environment Agency at least a week before they burn it, and the environmental health officer at your local council.

Burning alone doesn’t always destroy the rhizomes, so you’ll need to properly dispose of the remains after.

Bury it

You must check with the Environment Agency before you bury non-native invasive plants.

You can deeply bury Japanese knotweed at the site it’s growing if you:

  • Cover the plant remains with a material that doesn’t allow the plant to grow, such as a root barrier membrane
  • Do not bury it with any other types of waste
  • Bury it at a depth of 5 metres

You must also make sure the membranes used are:

  • Undamaged
  • Large enough to minimise the need for seals
  • Sealed securely
  • Able to remain intact for at least 50 years
  • UV resistant

It’s generally recommended that you hire a professional company to bury Japanese knotweed for you.

Can I get a mortgage on a property with Japanese knotweed?

For properties with Japanese knotweed, your mortgage lender will want to see assurances that it’ll be eradicated before agreeing to your mortgage payment.

If you're buying a home in an area with a large risk of knotweed but it hasn’t been discovered on your property yet (or if it’s been successfully treated in the past), your conveyancer may advise you to take out indemnity insurance.

Indemnity cover provides protection to buyers, mortgage lenders and successors in title if knotweed is discovered.

This could cover the cost of a survey report to confirm the presence of knotweed, the cost of treatment, repair of any damage caused and legal defences in the event of a third party being affected.

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