Section 701 establishes requirements for fire walls, which are complete separations created by noncombustible construction extending from the foundation to the roof deck or above. Fire walls are designed to prevent spread of fire from one building or area to an adjacent one, even if one side experiences complete collapse. Fire walls must extend through all concealed spaces, including cocklofts and crawlspaces, without gaps or penetrations except for approved through-penetration firestopping. Fire walls must be capable of free-standing support on either side, meaning each wall must remain in place even if one adjacent structure collapses. Foundations for fire walls must prevent shifting or separation. Structural framing on each side of a fire wall must be independently supported and capable of withstanding design loads without relying on the fire wall for lateral or vertical support. Window and door openings in fire walls are prohibited except under specific conditions including protected openings with rated frames and closures, or openings in low-hazard storage areas where opening size is limited. Utilities including pipes, ducts, and conduits must not penetrate fire walls unless absolutely necessary, and all penetrations must be protected with fire-rated sleeves and firestopping systems. Rated 2-hour fire walls are most common, though 3-hour and 4-hour ratings are required in certain hazardous occupancy situations. Fire walls separating different buildings are specifically prohibited from having door openings that would permit passage between structures. A fire wall effectively creates two separate buildings for code purposes.