Which tradesman to contact or how to describe a job

We had a leak in the connection to our washing machine (now repaired). We live in a tenement flat, staining has been caused to our downstairs neighbour. A surveyor has advised taking out the plaster board, brushing down the ash and removing the tiles under the washing machine to assess the joists. If the joists are affected, we will need to contact our insurance company to claim. I'm keen to get the wrk done ASAP, but not sure who I would need (builder or joiner) or which job drop-down best describes the work required. Thanks in advance.