DH has a condo built in 1989 that's been rented out for many years. It's going to be renovated this year. A flooring issue needs to be addressed.

The floors are a material that looks like plaster (covered with carpet). Over the years, the center of the living room floor has broken down and currently the center of the room (in front of the fireplace and where a living room furniture grouping would typically be placed) is lower than the floor at the edges of the room. It is noticable and would affect recarpeting. The floor needs to be leveled.

How do we determine what is needed and make sure a contractor knows what they are talking about? Any input would be appreciatd.