Buying a Property with Japanese Knotweed Damage? Here’s What RICS Category A Means for You

Over the next few weeks, we’ll be looking at the 4 different RICS Categories from A to D. This week we start with RICS Category A.

If you're house hunting and come across a property with Japanese Knotweed causing visible damage, it's likely classed as RICS Category A—the most serious level of infestation.

This means the knotweed isn’t just nearby—it’s already causing harm, like cracks in walls, damage to drains, patios, or outbuildings. It’s a major red flag for mortgage lenders and can seriously affect the property’s value.

Some lenders won’t lend at all on Category A properties. Others may consider it—but only if there’s a professional Knotweed Management Plan in place from a PCA-approved contractor, along with a 5 or 10-year insurance-backed guarantee, depending on lender requirements. Some lenders will not consider lending on a property with RICS Category A.

Treatment can be expensive and take years, so it’s important to go in with your eyes open. If you’re considering a home affected by Category A knotweed, make sure:
✅ A full survey has been done
✅ You’ve seen the treatment plan and guarantee
✅ You speak to a mortgage adviser who knows which lenders can help

Buying a home with Category A knotweed isn’t impossible—but it needs extra care, expert input, and the right plan in place to protect your investment.