[OrrieG]

Ditto, crawl underneath with a screwdriver. Rust never sleeps, if the PO did not at least cut out the bad and just covered from the top and tried to hide the bottom you have a problem. If he cut out the bad, and seal up the joints between the new and old then not so bad. Finishing it is your preference; leave it alone, smooth and paint, shag carpet??? If they replaced the whole floor and nothing else moved (window or door openings) its a bonus.