NO! If the Japanese Knotweed is in dormancy, we would strongly suggest you not to build. If you are looking to redevelop/landscape or disturb the ground, complete removal (excavation) of the Japanese Knotweed is advised, and although it would be a very costly program to remove the Japanese Knotweed, it would prevent any new build properties being affected by Knotweed down the line and potential claims being made against the developers.