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FIELD OF THE INVENTION 
     The present application relates to modular systems and methods for assembling multiunit buildings, and particularly to systems and methods wherein individual units are constructed from multiple vertically stacked modules. 
     BACKGROUND OF THE INVENTION 
     Increasing demand for affordable housing in major metropolitan areas has necessitated the development of creative systems for housing design. One such solution is the renovation of underutilized or functionally obsolete buildings, often former industrial sites, into housing units. One advantage of such units has been the ability to produce “loft” apartments, in which at least a portion of each unit has double-height ceilings. These apartments have become popular in many markets, to the point that demand for such units may exceed the available supply of buildings to retrofit. The present invention provides a solution to this shortage, by providing an affordable system for building such units from the ground up. 
     In addition to the limited supply of buildings suited to be converted to loft apartments, another major impediment to the construction of multiunit housing has been the need to provide adequate parking space for each unit. The present invention also provides a solution which allows inexpensive modular construction of living units over an associated parking area, so that a larger number of apartments may be placed in a given lot while conforming to local zoning codes and providing adequate parking facilities. 
     SUMMARY OF THE INVENTION 
     The present invention provides a modular system of construction of loft apartment buildings. This type of unit is in high demand in many metropolitan areas, and the modular nature of the inventive buildings allows them to be produced quickly and at low cost. In addition, the invention provides a novel system for interconnecting apartments quickly during construction, providing further cost savings. A mix of apartment types, including handicap-accessible apartments, may be placed in each building, with the proportions of different apartment types being tailored to the needs of the local market and the constraints of local building codes. The apartment modules may be sized to permit convenient shipping of modules within the constraints of overland shipping regulations. 
     In one aspect, the invention comprises a multiunit building having a modular structure, in which each unit of the building is formed from a pair of vertically stacked modules. At least one room of the unit (hereinafter referred to as a “great room”) extends from the floor of the lower module to the ceiling of the upper module (i.e., the unit is a loft apartment). 
     In one aspect, the invention comprises a multiunit building of modular construction, wherein multiple units of the building are each formed from two prefabricated modules, a lower module comprising a floor and four wall sections, and an upper module comprising a ceiling and four wall sections. At least one room of the unit extends the full height of the unit, i.e., from the floor of the lower module to the ceiling of the upper module. The unit may have a mezzanine level, in which at least one room is substantially contained within the upper module. The units may be arranged horizontally, vertically, or both. The building may also comprise lobby units, which may be vertically stacked and connected by a staircase and/or an elevator. The modules may be sized to comply with overland shipping regulations for transportation on a flatbed truck. 
     In another aspect, the invention comprises a method of building construction, comprising installing a foundation, placing a lower building module above the foundation, placing an upper building module on the lower module and securing the modules together. The modules combine to form a building unit, in which at least one room spans the distance from the floor of the first module to the ceiling of the second module. Multiple units may be placed vertically, horizontally, or both. Horizontally adjacent units may be connected by a utility feed. The modules may be constructed remotely and transported to the building site. 
     In still another aspect, the invention comprises a multiunit modular building, wherein horizontally adjacent units are connected via a corridor and a horizontal utility chase containing a utility feed. The utility feed may include water pipes, electrical wiring, communications and security systems, and life safety systems. The building may further comprise a lobby unit connected to the building units. Both building units and lobby units may be vertically stacked, and stacked lobby units may be connected via a vertical utility chase. 
     In yet another aspect, the invention comprises a method of constructing a modular building comprising installing two units, each containing a corridor section and a horizontal utility chase section containing a utility feed, and connecting the units and the utility feeds. The utility feeds may include water pipes, electrical wiring, communications and security systems, and life safety systems. The units may each comprise two vertically stacked modules as described above. The building may further contain one or more lobby units which may be connected to the utility feeds, and which may be stacked. Stacked lobbly units may be connected via a vertical utility chase. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention is described with reference to the several figures of the drawing, in which, 
     FIG. 1 is a cutaway view of an assembled apartment building comprising four apartment types according to the invention; 
     FIG. 2 is an exploded view of a “base” apartment of the building of FIG. 1, showing how two modules are stacked to form the apartment; 
     FIG. 3 is a cutaway view of the apartment unit of FIG. 2; 
     FIG. 4 is a perspective view of two units as shown in FIG. 2, illustrating corridor access and utility chase connections; 
     FIG. 5 is an exploded view of an “intermediate” apartment of the building of FIG. 1; 
     FIG. 6 is a perspective view of two units as shown in FIG. 5, illustrating corridor access and utility chase connections; 
     FIGS. 7 a - 7   f  are perspective and cutaway views of each unit as placed in an assembled building; and 
     FIG. 8 shows a lobby unit for use with the units pictured in FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     The invention is described below with reference to certain preferred embodiments, in which an assembled apartment building comprises three types of living units, placed upon a conventional (nonmodular) semi-depressed parking level. It will be understood by those skilled in the art that this represents only one embodiment of the invention, and the invention encompasses many modifications and variations of the structures described herein. For example, the number, size, and shape of the living units may be varied over a wide range. The apartment units need not all be loft units; in fact, it may be desirable to include some single-level units in order to comply with handicap-access regulations. The outer walls of each unit need not be coplanar as shown below; 
     the invention also contemplates staggered or offset arrangements of units. Further, the principles of the invention may be applied to the construction of multiunit office or industrial buildings, as well as living units. Commercial and dwelling units may even be mixed in a single building, within the constraints of local building codes. 
     An apartment building according to the invention is illustrated in cutaway view in FIG. 1, generally as  10 . The building  10  comprises three types of living units: base units  12 , two stories of intermediate units  14 , and top units  16 . The illustrated building  10  also comprises a semidepressed parking level  18 . The size and shape of units  12 ,  14 , and  16  may be more clearly seen in FIGS. 7 a - 7   f.    
     An exploded view of a base unit  12  is shown in FIG.  2 . The unit comprises a lower module  20  and an upper module  22 . Lower module  20  comprises a floor  24  and four vertical outer walls  26 . Upper module  22  comprises a ceiling  28 , four vertical outer walls  30 , and a floor section  32 . Floor section  32  spans only a portion of the module. Thus, when the modules are stacked to form the apartment unit, the unit comprises a great room  34  which has a floor-to-ceiling height spanning the two modules. Large windows  36  are preferably provided for the great room  34  to further increase the spacious feeling of the room afforded by the high ceiling. The rear section  38  of the apartment comprises floor-level rooms having section  24  as their floor, and mezzanine rooms having section  32  as their floor. Internal stairs  40  (more clearly seen in FIG. 3, a cutaway view of the same unit) allow access to the mezzanine level from the floor level. 
     It is preferable that modules  20  and  22  conform to overland shipping regulations for easy transportation. For example, a module may have a width not exceeding 14 feet, a length not exceeding 66 feet, and a height not exceeding 11 feet. These sizes are exemplary, and may be adjusted depending on the 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 FIG.  4 . 
     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 “plugged in” 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 the building is assembled. 
     The ease of connection of the building services also facilitates on-site “finishing” of the apartment unit. In this concept of building construction, module  22  is stacked atop module  20 , and chase utility feed connections to the previously installed adjacent unit are immediately made. The newly installed unit  12  is then immediately powered, and workmen can simply turn on the preinstalled lights and plug power tools into existing wall outlets in order to finish securing the modules together and to the adjacent unit, and to install cosmetic elements such as molding to cover the module joints. In addition, construction site security can be maintained by immediate connectivity to a central security monitor specifically equipped for temporary duty on the active construction sites. Sprinkler systems can be activated far in advance of conventional construction methods, reducing the risk of damage by fire. 
     A second type of unit  14  is illustrated in FIG.  5 . The modules  46  and  48  making up the unit  14  are of approximately the same size and shape as modules  20  and  22 , but they combine to form different apartment shapes. The apartments does not stretch across the full width of the building  10  as does unit  12 ; instead, each apartment is approximately one-half the length and twice the width of unit  12 , and separate apartments are placed on opposite sides of the corridor  50 . The units on either side of the corridor need not be identical in space or layout, if it is desired to have a building with a variety of apartment configurations. In order to provide utility feeds for apartments on either side of the corridor  50  in this configuration, it is preferable to place the horizontal utility chase  52  under (as shown) or over the corridor  50 . Access panels may be placed in the floor (or ceiling) corridor  50  if desired, but it will generally be found preferable to access the utility chase  52  from inside the apartment units in this configuration. FIG. 6 is a perspective view of two assembled units  14 , with corridor  50  and utility chase  52  connections extended for clarity. 
     A third type of unit  16  for placement on the top level of the building  10  is shown in FIGS. 7 e  and  7   f . As pictured, this unit comprises three modules and is three times the width of unit  12 . It will be apparent to those skilled in the art that other unit shapes and sizes may also be used. As shown, unit  12  is a single-level unit (which may be made handicap-accessible if desired), but the top unit may also have a mezzanine if preferred. The modules making up this unit preferably comprise integral membrane roofing and roof drains, and may further comprise skylights, coffered ceilings, clerestories or the like to enhance the perception of light and space in the units. Unit  16  comprises horizontal chases, as do the other units  12  and  14 , for rapid connection of adjacent units. 
     Buildings according to the invention are extremely economical in space usage. For example, in a preferred embodiment, the height X of units  12  and  14  may be 18 feet. The height Y of units  16  may be 10.5 feet, and the elevation of ground floor units  12  above the grade Z may be 5.5 feet, for a total building height of 70 feet. This configuration falls within the Building Officials and Code Administrators (BOCA) International standard for Type  3 A construction of a multi-family, fully sprinklered building. (Because mezzanine areas are limited to ⅓ the area below them under the BOCA definitions, the pictured unit is considered a four-story building, and falls within the five story limit for a building of this type. Because the standard allows a five story building of this height, it may be desirable for the upper levels in one floor of apartments to be expanded, offering greater flexibility in apartment design). 
     At least one vertical chase  54  is provided for the building in order to connect the daisy-chained horizontal chases of each level of the building to a central utility feed. This vertical chase may run parallel to an elevator shaft  56 , for example, in order to provide further space savings. FIG. 8 shows a modular unit for a lobby area, from which two rows of units  14  may extend. (While the pictured unit is configured for connection with unit type  14 , it will be apparent to those skilled in the art that lobby units for connections to unit types  12  and  16  can easily be constructed). Apertures  58  are provided for connection with the corridor  50 , and apertures  60  are provided for connection with the horizontal chase  52 . The lobby further comprises emergency stairs  62 . 
     The length of base units  12  is preferably somewhat longer than that of the upper modules. This additional length ensures an interior width inside the foundation walls suitable for ease of parking and maneuvering, and serves as a basis for articulating the architectural base of a building constructed according to the invention. The extra length further serves continuous, uninterrupted bearing walls for the units above. 
     All units  12 ,  14 ,  16  are preferably constructed with “hard-shell integrity,” allowing improved fire safety and sound deadening (high STC for residential construction). The integral roof construction of the top units  16  means that any roof failure is localized and the possibility of collateral or residual damage is minimized. 
     The buildings of the invention can be constructed extremely rapidly. An exemplary  96 -unit building in the configuration shown in FIG. 1, for example, may be constructed in a period of about 16 weeks. Preferably, construction begins with laying of the building foundation and construction of the semidepressed parking structure, if included. A column of level lobbies, containing the elevator shaft and vertical utility feed is then constructed, and building units can then be placed in one or more wings extending from the lobby area. It will generally be found preferable to add modules to the building in stacks, placing all levels over a given base unit  12  before placing the next base unit, but construction may also proceed by placing all ground level units, followed by all second level units, etc. 
     It will generally be preferable for modules to be finished as much as possible in the factory, before shipping to the building site. This is facilitated by the horizontal chase structure which allows utility feeds to be placed in the chase during manufacturing, so that only splices between units need be completed in the field. The attachment of the lower module  20  to the upper module  22  must be accomplished in the field, but much of the initial machining (e.g., drilling holes, providing quick-connect fittings for ductwork and plumbing) may be accomplished at the factory, and all necessary hardware may be placed in one of the modules during the manufacturing process, allowing quick and easy connection of the modules. Carpeting, windows, etc. may all be preinstalled at the factory, allowing improved working conditions for installation personnel and lower costs for the manufacturer. 
     Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Summary:
A modular system of construction of loft apartment buildings. This type of unit is in high demand in many metropolitan areas, and the modular nature of the inventive buildings allows them to be produced quickly and at low cost. In addition, the invention provides a novel system for interconnecting apartments quickly during construction, providing further cost savings. A mix of apartment types, including handicapped-accessible apartments, may be placed in each building, with the proportions of different apartment types being tailored to the needs of the local market and the constraints of local building codes. The apartment modules may be sized to permit convenient shipping of modules within the constraints of overland shipping regulations.