I am in the process of extending and renovating my house. Whilst stripping the main bathroom, the builder removed what used to be the shower bath. I noticed some rotten timbers and joist beneath. I expressed concern about this to him, and he assured me that he would simply replace the damaged bits then move on. I have asked him to replace all the floorboards instead, since he is placing new floorboards in the extended area of said bathroom. He has now placed a new (greenwood) joist in the floor directly against the old rotten one. Apparently, when asked if it was best to remove it, he stated that this isn't necessary. Am I just panicking unecessarily or should he have removed part of the old joist before placing the new one? Any advice...?