When should a fire alarm system be brought up to the current standard and building codes?

The repair, restoration, reconstruction, improvement, or remodeling of a public building, a commercial establishment, or a multifamily residential dwelling consisting of four or more units for which the cost exceeds 50% of the building’s value according to the certified tax appraisal roll for the county for the year preceding the year in which the work was begun; or, a change in occupancy classification involving a change in the purpose or level of activity in a building, including the renovation of a warehouse into a loft apartment. For purposes of determining if an improvement is a Substantial Improvement, the applicant for a permit must submit data reflecting cost of the improvement, restoration, reconstruction, improvement or remodeling. Costs shall include the value of all labor and materials. A permit is required prior to the start of any Substantial Improvement.