In a residential or commercial district where any sign does not comply with the provisions of this chapter, such sign and any supporting structures may be maintained but shall not be replaced, reconstructed, moved, structurally altered, repainted or relighted except in compliance with the provisions of this chapter and may continue in use unless subject to removal under other provisions of this chapter. The removal, replacement, reconstruction, moving or structural alteration for any cause whatsoever shall be considered as loss of nonconforming status.