Platforms, stair units, landings, and guardrails link to create an additional vertical level in a facility, providing additional floor space for work or storage. Their modular architecture enables warehouses and other large facilities to expand their usable space without the mess and interruption that comes with traditional construction. The structure's floor is made up of mezzanine platforms. Lower levels can access the platform via mezzanine stairs and landings. Guardrails on mezzanine platforms act as a barrier, preventing people and equipment from falling over the edge of the platforms.