I recently bought a single family frame house in NYC that was built around 1920. During renovations, my contractor pointed out that the 2nd floor saggs about 1 3/4" towards the center of the house. The floor joists are 2x6, 16" on center, spanning a 16 foot width with wood plank sub-flooring. The house is 16 ft x 40 ft. During demo, there is evidence of gas and water pipes indicating that the main area that sags may have been a kitchen. Everyone I've spoken to said that for the age of the house, a 1 3/4" sag is nothing to be concerned about. I know fixing it would be very costly. I'm wondering if once my I move in, will it continue to sag further and cause more problems in the future. Does anyone have any advice about this?