If your home has had previous owners, you can often tell it they’ve done remodels involving structural walls by looking for these red flags : 1) Unusually large rooms for old houses. 2) Unusual seams on ceilings and floors. 3) Floors that slope in some rooms but not others. 4) Mismatched trim work on doors and baseboards. 5) Cracks in the plaster above windows or doors.