Japanese knotweed
Does a RICS knotweed management category tell you how much to take off the price?
No. The 2022 categories describe whether knotweed is damaging a structure, affecting amenity, or sitting off site within three metres. The Property Journal notes that the effect on value differs for those reasons. It does not publish a percentage to deduct, and neither does this page.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Category A is visible material damage to a significant structure. Category B is no such damage, but use of amenity space is likely to be restricted. Category C is neither damage nor an amenity restriction, so any remediation is at the owner’s discretion. Category D is an infestation off site within three metres of the boundary. Those are reporting categories. A remediation specialist still has to say what action, if any, is appropriate. The journal says that in all cases where knotweed is seen within the boundaries, the client should be pointed to that specialist.
A price conversation is between you, the seller and your solicitors, using a specialist’s scope if you have one. The category is not an invoice. Lender attitudes differ and are not set by RICS in that journal. Ask the lender what they want. Do not invent a reduction because a forum used one.
What should you ask your surveyor?
- Which category are you reporting, and what did you see that put it there?
- Are you making a valuation deduction, or only a management category?
- What should the specialist be asked to price?
What are the typical next steps?
- Get a specialist’s recommendation before you name a figure.
- Ask your lender what evidence they want. Do not assume every lender treats every category the same way.
- Put any price conversation through your solicitor, in writing.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does category C mean the value is untouched?
The journal says the impact on value is much lower because damage and amenity are not affected, and remediation is discretionary. “Lower” is not a number. Do not write £0 unless the specialist and the lender agree there is nothing to do.
Can you average categories A and D?
No. They are different facts: damage on site, or a plant next door. Report the one that applies.