A Home inspection is not a code inspection and should not be confused with code compliance inspections conducted by most municipalities for new constructions and for renovations or certain repairs.
A home inspection is a visual inspection of readily accessible structural components and systems to determine if they are providing their intended function safely at the time of the inspection. It is intended to document visible defects or conditions that in the opinion of the inspector based on his or her knowledge and training would adversely affect the function of the system or component.
Homes built 30-40 years ago were built to a different standard than homes built today and therefore should not be compared to newer homes when inspected. Although many improvements have been made in minimum building standards homes, built 30, 40 or more years ago, when properly maintained are capable of providing many more years of service. As structures and components age they require repair, service and/or replacement. In some cases it may not be possible for components to continue functioning as they were originally installed and designed to function. In that case current standards should be used for the repair or replacement which may also require other areas to be repaired or modified.
To simplify, a component that is providing its intended function safely as it was originally designed and installed to, should in most cases be considered serviceable.
A component that is not functioning safely or is no longer functioning as it was originally installed and designed to, should be properly documented per applicable Standards of Practice depending on the nature of intended function.
Home Inspection Standards of Practice spell out specific standards to be followed when conducting a Home Inspection as well identifying areas that are beyond the scope of a Home Inspection. Links to the Standard of Practice from the American Society of Home Inspectors and the National Association of Home Inspectors are listed below for further reference.