I know if we cut into the party walls to set in the RSJ this will invoke PWAs. But what if we leave the end portions of the old wall standing and rest the RSJ on those. Will this avoid a PWA..S Builders New Member. The party wall should be 9 inch thick so you can take out 4 inches which (will be your side)without disturbing the neighbours.Even tho you will only have 100 -110mm bearing this is ok in this situation.