If a building which houses a nonconforming use is destroyed accidentally due to fire, explosion or other cause to an extent not exceeding 50% of its true value, as determined by the City Tax Assessor, such building may be restored within one year in substantially the same size, form and location, and the same nonconforming use may be reinstated without being extended. If destroyed to a greater extent, such building may be restored but only to house a conforming use.