method of shipping used and on local shipping regulations for example greater size flexibility may be afforded when it is practical to ship the units by barge ship or helicopter or when the modules are constructed at a location near the building site access to the unit 12 is afforded by a corridor 42 which opens onto the mezzanine level it will be seen that when multiple units 12 are placed side by side to form a building level the corridors 42 will connect to form a joint accessway to the individual apartment units a pair of units with connected corridor sections 42 can be seen in fig4 shown adjacent to the corridor 42 is a horizontal chase 44 whereby building services such as water pipes electrical wiring communications and security systems and sprinkler and other life safety systems not shown may be provided it is an advantage of this type of building module that access to water pipes and the like may be provided by an access panel not shown on the common corridor 42 removing the necessity for workmen to enter individual apartments when performing maintenance it is a further advantage of the horizontal chase 44 that it facilitates easy connection of building services such as water and electricity pipes and wiring may be preinstalled in the chase when the unit is constructed so that they need only be u201c plugged in u201d to an adjacent unit 12 when the building is assembled on site the prior art almost exclusively uses vertical chases for these services so that pipes and wires must be fed through the chase by hand after.