Got Knotweed Next Door? Here's What RICS Category D Means

We’ve talked about Categories A to C—now let’s look at RICS Category D, which covers Japanese Knotweed growing on neighbouring land, not on your property.

Even if knotweed isn’t inside your boundary, lenders and surveyors still pay attention. That’s because there’s a chance it could spread—especially if it’s close by and not being managed.

The good news? Category D is considered low risk. In most cases, the impact on your property’s value is small. But if the knotweed next door is extensive or unmanaged, it could raise questions—maybe even legal concerns. Some lenders might hesitate if the infestation looks severe.

You can’t force your neighbour to remove or treat it, which can be frustrating. But since it’s out of your hands, most lenders won’t expect you to fix it.

If you’re in this situation, don’t panic. It’s usually manageable. Just keep an eye on the growth and, if needed, speak to a knotweed specialist for advice. Being informed is your best defence—and can save a lot of stress during a sale or mortgage application.