[plumb4u2]

I am recommending hand held saw due to the fact that it is a basement and I am assuming that access may be tight in some areas

A large hand held chop saw is a wonderful tool and easy to use and maneuver....I own both hand held and walk behind

A walk behind is an awesome tool however he is going to be cutting close to the wall and into corners, a walk behind may be too cumbersome in this application

I typically only use the walk behind when Im cutting customers driveways in order to replace sewer or water service