Section 603 establishes the specific fire-resistance ratings required for primary building elements including structural columns, beams, floor-ceiling assemblies, roof-ceiling assemblies, and bearing walls for each construction type. Type IA construction requires 3-hour fire-resistance for primary structural elements, floor-ceiling assemblies, and roof-ceiling assemblies, representing the highest fire-resistance requirement in the code. Primary structural elements include main supporting columns, girders, and beams. Bearing walls are the exterior and interior walls that support floors or roofs above. Type IB construction requires 2-hour fire-resistance for primary elements and floor assemblies, with 1-hour for roof-ceiling assemblies and exterior walls. Type II noncombustible construction has no required fire-resistance ratings but mandates noncombustible materials throughout. Non-structural elements may be unrated in Type II construction if they are noncombustible. Type III construction requires 1-hour fire-resistance for floor-ceiling assemblies and 2-hour for exterior bearing walls. Combustible interior elements are permitted. Type IV heavy timber construction requires 1-hour fire-resistance for floor-ceiling assemblies and 2-hour for exterior walls, achieved through the inherent properties of large solid wood timbers. Type V unprotected construction has no required fire-resistance ratings, while Type V protected requires 1-hour ratings for certain elements including exterior walls and floor-ceiling assemblies in buildings exceeding certain area or height limits.