The useful life of farm buildings

Whether we work on a farm or in the city, we all live in a house or apartment. Whether the dwelling is new or a century home, many of us appreciate the charm of an old house.
As we get older we may want ground level access without steps, and doors wide enough to allow wheelchair access. While some homes that are only a few decades old are demolished to be replaced by new, more efficient homes, some old century homes remain very comfortable and saleable to the next generation.
For buildings that are used to carry on a profitable business in — be it an assembly line where Ford cars are built, a barn where animals are housed or a shed where farm equipment is stored — design requirements change.