US 20020046521 A1
A pre-cast building system includes a plurality of modular, pre-cast components. There is an elongate footing component having an upwardly facing longitudinal channel and a longitudinal first keyway section formed therein. One end of the footing component carries a pocket and the opposite end carries an insertion member for interengaging the pocket of an adjacent, aligned footing component. An elongate foundation component is received in the channel. A lower edge of the foundation component includes a second, complementary keyway section that faces the first keyway section to form an elongate keyway that receives a bonding adhesive. An exterior wall component is interengaged with the opposite upper edge of the foundation wall component. A pair of opposing receptacles are formed respectively in the upper edge of the foundation component and the lower edge of the exterior wall component. These receptacles face one another and receive a connector component that interlocks the foundation component and the exterior wall component. The inside surface of the foundation component carries a longitudinal ledge on which a peripheral portion of a pre-cast floor slab is supported. The upper edge of the exterior wall panel includes an inverted receptacle that accommodates a roof tie down component such that the positioning of the component may be adjusted.
1. A precast building system comprising:
an elongate footing component including an upwardly facing longitudinal channel that has a longitudinal first keyway section formed therein;
a foundation wall component received by said channel and having an elongate second keyway section facing and generally aligned with said first keyway section, said generally aligned keyway sections defining an elongate keyway for receiving an adhesive material to secure together said footing and foundation wall components; said foundation wall component further including a first receptacle formed in an upper edge thereof; and
an upper wall component that interengages said foundation wall component and having a lower edge that includes a second receptacle opposing said first receptacle, said first and second receptacles receiving a connector element, said receptacles and said connector element being configured to hold together said upper wall component and said foundation wall component.
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21. A pre-cast building system comprising:
an elongate footing component having a longitudinal first keyway section formed therein;
a foundation wall component interengaging said footing component and having an elongate second keyway section facing and generally aligned with said first keyway section, said generally aligned keyway sections defining an elongate keyway for receiving an adhesive material to secure together said footing and foundation wall components; said foundation wall component further including a first receptacle formed in an upper edge thereof; and
an upper wall component that interengages said foundation wall component and having a lower edge that includes a second receptacle opposing said first receptacle, said first and second receptacles receiving a connector element, said receptacles and said connector element being configured to hold together said upper wall component and said foundation wall component.
 This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/201,235 filed May 1, 2000.
 This invention relates to a pre-cast building system and, more particularly, to a system that employs a plurality of modular pre-cast concrete components that are assembled more quickly and efficiently, and far less expensively than the components of conventional building systems.
 Construction of a conventional cement block building is typically a very involved process, featuring various tasks that must be carefully coordinated. For example, initially a footing trench is excavated and reinforcing steel is arranged in the trench. The job is then halted while the work is inspected. After inspection, concrete footings are poured and cement blocks are installed to create a foundation wall. The dirt within the foundation is then graded and compacted. Construction is stopped again to allow the plumber, air conditioning contractor and electrical contractor to install appropriate pipes and conduits. Each of these installations must undergo multiple inspections. Eventually, a concrete floor is poured and finished. After the floor is allowed to sufficiently harden, concrete blocks are assembled to form the exterior walls of the building. A further inspection of the reinforcing steel used in the blocks is then required. After the cement blocks are installed, the concrete finishing work must be performed. Skilled concrete artisans complete a number of finishing tasks before the roof of the building is installed. Immediately before the roof is constructed, the workers insert steel anchors into the concrete at the top of the wall to fasten the roof framing members to the wall. These anchors must be installed at precise locations and depths. The foregoing construction process is complicated even further when a wood floor system employing a tie beam is involved. Standard poured or pre-cast concrete buildings employ an analogous procedure. Instead of using blocks, concrete forms are utilized to build the foundation and exterior walls.
 The known concrete construction techniques described above are fairly complex, time consuming and expensive. Multiple crews of highly paid skilled tradesmen are required to perform the respective tasks. Work schedules must be precisely coordinated. Delays in the delivery of materials, adverse weather conditions, inspection delays and other problems can be extremely costly and detrimental to the project, particularly when time is of the essence. One or more errors or miscalculations during construction can delay the project and drive up costs even further. Human error frequently accompanies the assembly and installation of the concrete building components. Mistakes are particularly common because each of the primary components (e.g. footing, foundation and exterior wall) is built “in the field”, i.e. at the job site.
 A need currently exists for a simpler, more efficient concrete building system, which utilizes modular parts and which can be installed quickly and precisely, with little risk of error, even when inexpensive, unskilled workers are used to perform the work.
 It is therefore an object of this invention to provide a highly efficient pre-cast building system that permits a concrete building to be constructed much more quickly and more accurately, but far less expensively than previously accomplished using conventional concrete and cement block building systems.
 It is a further object of this invention to provide a building system employing modular concrete components pre-cast in a factory rather than in the field so that expense is reduced and quality control is significantly improved.
 It is a further object of this invention to provide a building system that may be installed rapidly and relatively inexpensively, even by a fairly small team of unskilled or semi-skilled workers.
 It is a further object of this invention to provide a building system that significantly reduces the need for multiple inspections at various points of the construction process and which thereby significantly reduces construction delays and costs.
 It is a further object of this invention to provide a building system that may be reliably assembled in a virtually fail-safe manner thereby reducing construction delays and cost overruns.
 It is a further object of this invention to provide a building system that permits roof tie downs to be positioned quickly, conveniently and accurately even by unskilled laborers.
 It is a further object of this invention to provide a pre-cast concrete building system employing modular components that interlock simply and securely and which provide the finished building with exceptionally strong structural integrity and durability.
 It is a further object of this invention to provide a pre-cast concrete building system that exhibits extremely high quality but at far less cost than that of conventional construction systems.
 It is a further object of this invention to provide a pre-cast concrete building system that achieves an aesthetically attractive building.
 It is a further object of this invention to provide a building system that is extremely resistant to severe weather, fire and insect intrusion.
 It is a further object of this invention to provide a pre-cast concrete building system that is extremely energy efficient.
 This invention features a pre-cast building system including a plurality of pre-cast modular components composed of concrete or other suitable building material. Specifically, this system includes an elongate footing component that is installed within a trench in the ground. The footing component includes an upwardly facing longitudinal channel that receives a lower edge of an elongate foundation component. A longitudinal first keyway section is formed in the channel of the footing component. That keyway section faces and is generally aligned with a complementary second longitudinal keyway section formed in the lower edge of the foundation wall component. The aligned keyway sections define an elongate keyway. An adhesive material is introduced into the keyway to secure together the footing component and the foundation wall component. The foundation wall component also includes an interior lip or ledge that supports a floor slab of the building. An upper or exterior wall component includes a lower edge that interengages an upper edge of the foundation wall component. A pair of opposing receptacles are formed respectively in the upper edge of the foundation wall component and in the lower edge of the exterior wall component. The receptacles include complementary configurations that enable the opposing receptacles to receive a connector element that secures together the exterior wall component and the foundation wall component.
 In a preferred embodiment, the abutting keyway sections in the footing component and the foundation wall component have opposing dovetail shapes. The opposing receptacles in the foundation wall component and the exterior wall component may include complementary “T” shapes and each of the opposing receptacles may extend longitudinally for the length of the foundation wall component and the exterior wall component, respectively. The connector element may have a generally “Z” shaped configuration that fits within the aligned “T” shaped receptacles to hold together the foundation wall component and the exterior wall component.
 One of the longitudinal ends of the foundation wall component may include a tongue and the other end of the foundation wall component may include a complementarily shaped groove. When a pair of foundation wall components are aligned and abutted, the tongue of one of the components is receivable in the groove of the other component to interlock the adjoining components. Similarly, each exterior wall component may include a vertical edge that carries a longitudinal tongue. The other vertical edge of the exterior wall component may carry an elongate groove that receives the tongue of an adjacent exterior wall component to interlock a pair of adjoining exterior wall components. One end of each footing component may carry an upwardly facing pocket and the opposite end of the footing component may carry a downwardly facing peg or insertion member. When a pair of footing components are aligned and interengaged, the peg of one of the components is inserted into the pocket of the adjacent component to interlock the adjoining components. The orientation of the pocket and the insertion member may be reversed. An adhesive may be introduced between the tongue and groove interconnections of the exterior wall and foundation wall components as well as between the pocket and peg of the adjoining footer components.
 The building system of this invention may also include assorted comer components. For example, a corner footing component may include a pair of elongate footing sections that are unitarily interconnected at an angle of 90° or otherwise. Each of the elongate footing sections may include a longitudinal channel and a longitudinal keyway section within the channel, analogous to the elements previously described for the elongate footing components. The channel and keyway sections of the respective footing sections interconnect at the same angle at which the footing sections interconnect. Each elongate footing section of the corner footing component may carry at its distal end either a pocket or insertion member as previously described. These parts interengage with complementary connecting parts (i.e. a pocket interengages an insertion member and vice versa) carried by adjoining elongate footing components.
 A corner foundation wall component may include simply an elongate member having a receptacle and an interior ledge as previously described. In this piece, the ledge does not extend for the entire length of the component. Rather, it stops short of one end of the component and thereby forms a notch proximate that end of the corner component. A transverse tongue is formed on the comer component within the notch. The notch receives a complementary end of an adjacent standard foundation wall component such that the groove formed in one end of the latter component receives the transverse tongue of the corner component. As a result, a completed foundation corner part is formed.
 A corner exterior wall component may include a pair of panels permanently interconnected at an angle of less than 180° and preferably about 90°. An elongate wall groove is formed in the distal vertical edge of one of the panels and an elongate tongue is formed along the distal vertical edge of the other panel. Each panel includes a receptacle analogous to that previously described and formed in the bottom edge of the panel. The receptacles in the respective panels intersect proximate the vertex of the component. The corner exterior wall component interengages and interlocks with a pair of previously described exterior wall components. The tongue carried by the vertical edge of one of the corner panels fits into the groove of an adjoining exterior wall component. The groove carried along the vertical edge of the other corner panel receives the tongue of a second exterior wall component.
 The upper edges of the exterior wall component and the corner exterior wall component may include a longitudinal receptacle. That receptacle may have a general T-shaped cross-sectional configuration for receiving a roof truss tie down component in a slidable fashion.
 Each receptacle described herein may comprise an insert that is pre-cast into its respective component. The insert has an opening with the configuration described above (e.g. the “T” shaped configuration) for receiving an associated connector element (e.g. the “Z” shaped connector interengaging the foundation wall and exterior wall components, and the typically “L” shaped roof truss tie down component attached at the upper edge of the exterior wall component).
 An upper surface of the ledge carried by the foundation wall component may include a longitudinal groove. The groove receives a seal that restricts passage of insects between the floor slab and foundation wall component.
 Transverse holes may be formed through the footing components and the corner footing components to reduce the weight of those components.
 Other objects, features and advantages will occur from the following description of a preferred embodiment and the accompanying drawings, in which:
FIG. 1 is a perspective, partially exploded view of a section of a building constructed utilizing the pre-cast building system of this invention; FIG. 2 is a cross sectional view illustrating the interengagement between the footing component, foundation component and upper or exterior wall component of the system;
FIG. 3 is an elevational view of a representative footing component;
FIG. 4 is an elevational end view of the footing component facing the end of the component that carries the insertion member;
FIG. 5 is an elevational end view of the footing component facing the end of the component that carries the pocket;
FIG. 6 is a top plan view of a corner footing component in accordance with this invention;
FIG. 7 is an elevational side view of a representative foundation component according to this invention;
FIG. 8 is an elevational end view of the foundation component taken along line D-D of FIG. 7;
FIG. 9 is a cross sectional top view of a pair of adjoining foundation components, which particularly illustrates the tongue and groove interconnection between those components;
FIG. 10 is a top plan view of a preferred corner foundation component according to this invention;
FIG. 11 is an elevational side view of a representative exterior wall component according to this invention;
FIG. 12 is a cross sectional view of the exterior wall component taken along line F-F of FIG. 11; and
FIG. 13 is a top plan view of a preferred corner exterior wall component according to this invention.
 There is shown in FIG. 1 a pre-cast building system 10 that comprises a plurality of modular pre-cast components designed to be assembled in a quick, efficient and very inexpensive manner, yet which provide superior structural integrity. It should be understood that each of the components of this system is typically composed of a conventional building material such as concrete. Various alternative substances that exhibit a high strength and that are suitable for use in building applications may also be employed. When cement or concrete components are employed, conventional rebar may be cast within the components to enhance the strength of the components. The specifics of the casting and reinforcing steps are well known to persons skilled in the art and do not comprise a feature of this invention.
 Building system 10 includes, as its principal parts, footing components 12, foundation components 14 and upper or exterior wall components 16. Each component is pre-cast. Components 12, 14 and 16 are interengaged in the manner best shown in FIG. 2. System 10 also includes pre-cast corner components. More particularly, as shown in FIG. 1, there is a corner footing component 18, a corner foundation component 20 and a corner upper or exterior wall component 22. The precise manner of interconnecting these corner components to one another and to the footing, foundation and exterior wall components is described more fully below.
 It should be understood that a typical building comprises a number of sections that include components 12, 14 and 16 interengaged as shown in FIGS. 1 and 2. A typical building will also include a number of interengaged corner components. The structure of a representative one of each of the components is described herein. It should be understood that a similar construction applies for each other modular component of a particular type.
 Footing component 12 is installed in a conventional footing trench formed in the building site. Component 12, which is depicted by itself in FIGS. 3-5, includes an elongate body portion 24 that supports a tapered, upwardly facing surface 26. At the upper end of surface 26 there is formed a raised longitudinal section 27 that contains a longitudinal, upwardly facing channel 28. A dovetail shaped first keyway section 30 is formed in the base of channel 28. Keyway section 30 extends for the entire length of the channel.
 As best shown in FIGS. 1 and 3-5, each footing component 12 carries a pair of extension sections 34 and 36 that are connected unitarily to respective ends of body section 24. Extension section 34 extends from one end of the footing component proximate the top of the component and second extension section 36 projects from the opposite end of the footing component proximate the bottom of the component. As best shown in FIGS. 1 and 4, extension section 34 supports an extension of the previously described tapered surface 26 as well as extensions of raised section 27, channel 28 and keyway section 30. The bottom surface of section 34 carries a downwardly facing insertion member or peg 38. This peg is unitarily connected to the remainder of extension portion 34 and has a generally rectangular or square configuration.
 As shown in FIGS. 1 and 5, each extension section 36 is unitarily connected to body section 24 of footing component 12. Extension portion 36 includes a generally square or otherwise rectangular shaped pocket 40 that faces upwardly. Extension sections 34 and 36 are constructed such that peg 38 and pocket 40 have complementary shapes and sizes and are positioned to interlockably interengage when the upper extension section 34 of one footing component overlaps the lower extension section 36 of an adjacent footing component 12. In this manner, a pair of adjoining footing components are secured together. An appropriate bonding agent may be introduced into the pocket to strengthen this interengagement. Any selected number of adjoining footing components may be interconnected in this manner to form a generally linear footing arrangement. When the footing components are so arranged, the channels 28 and keyway sections 30 of the respective footing components are similarly aligned to define a continuous channel and keyway section along the entire length of the assembled footing. As shown in FIGS. 1 and 3, each footing component 12 may include a plurality of transverse arches or openings 42. These permit the footing components to employ less material so that weight and cost are reduced. At the same time, strength and durability are not sacrificed.
 At each corner of the building, there is formed a corner footing component 18, FIG. 1. This component is similarly disposed in a standard footing trench and is typically interconnected between the ends of two transverse footing components 12. Each such component typically traces a respective side of the building. Corner component 18 is depicted by itself in FIG. 6. The corner footing component includes a pair of elongate footing sections 50 and 52, which are unitarily interconnected at an angle of 90° or otherwise. Typically, the corner footing section is pre-cast or molded in a single piece. Alternatively, multiple pieces may be used. Each footing section of the corner component includes an elongate body 24 a, best shown in FIG. 1. A tapered upper section 26 a extends upwardly from body section 24 a. A raised section 27 a extends upwardly from tapered section 26 a. A channel 28 a extends longitudinally through each of the footing sections 50 and 52. A generally dovetail shaped keyway section 30 a having a size and configuration identical to previously described keyway section 30 is formed through each of the footing sections 50 and 52. As best shown in FIG. 6, the channels 28 and keyway sections 30 a of the respective footing sections 50 and 52 join in a mitered fashion at the junction of sections 50 and 52. As a result, channels 28 a and keyway sections 30 a form a perpendicular angle.
 Each corner component 18 also includes a pair of corner extensions 54 and 56, FIGS. 1 and 6. Each extension projects from the distal end of one of the sections 50 and 52 and, more particularly, from the body section 24 a of that particular footing section. A rectangular pocket 40 a having a size and shape that are analogous to previously described pocket 40, is formed in each of the upwardly facing surfaces of extension sections 54 and 56. Each of the pockets lockably receives a respective peg 38 that projects downwardly from and adjacent footing component 12. Once again, a suitable adhesive may be placed in pockets 40 a. In this manner, each linear section of interconnected footing components 12 is secured to a respective section 50, 52 of corner footing component 18. In alternative versions, the insertion members and pockets may be reversed such that the corner component carries pegs and the elongate footing components have pockets that engage those pegs. As with the linear footing components 12, corner component 18 includes a plurality of transverse arches or holes 42 a, which reduce material, weight and expense, while maintaining strength of the component.
 A representative one of the linear foundation components 14 is depicted in FIGS. 7 and 8. Component 14 includes a panel 60 that features a flat outer surface 62. The inner surface 64 of component 14 carries a unitary lip or ledge 66. As best shown in FIG. 2, ledge 66 supports the peripheral edge of a standard concrete floor slab 68. The ledge is positioned along inside wall 64 of component 14 such that when slab 68 is laid within the foundation, the upper surface 70 of the slab is generally level with the upper edge 72 of component 14. The upwardly facing surface of ledge 66 preferably includes a longitudinal groove 74. That groove receives a seal 76 that interengages ledge 66 and the bottom surface of slab 68. Seal 74 prevents insects from intruding into the finished building between foundation component 14 and slab 68.
 Foundation component 14 includes lower and upper edges 72 and 74 respectively. As best shown in FIG. 2, lower edge 74 is received within longitudinal channel 28 of footing component 12. A second dovetail shaped keyway section 78 is formed longitudinally in lower edge 74 of component 14. Keyway section 78 faces the first keyway section 30 formed in footing component 12. As a result, the opposing keyway sections 30 and 78 define an elongate locking keyway. Foundation component 14 is inserted into footing component 12 in the manner shown in FIG. 2. An adhesive grout or similar bonding substance is pumped through the aligned keyway sections 30 and 78. This material is allowed to harden, which permanently secures foundation component 14 within channel 68 of footing component 12. Channel 68 is approximately 2″ deep so that the foundation component may be adjusted relative to the footing component. This enables the foundation component to be quickly and conveniently leveled when necessary.
 A receptacle 80 is formed in upper edge 72 of wall component 14. Receptacle 80 preferably extends for the entire length of component 14 and includes a generally inverted T-shaped cross sectional configuration. The receptacle may simply comprise a void formed or cast into the upper edge of the foundation component, although preferably, the receptacle is defined by a metal or plastic insert having the cross sectional shape depicted.
 As best shown in FIGS. 7 and 9, one vertical side edge of component 14 carries an elongate tongue element 82. The opposite vertical side edge of the foundation component includes an elongate groove 84 formed therein. Tongue 82 and groove 84 include complementary tapered shapes, best shown in FIG. 9. Each component 14 includes a tongue along one vertical edge and a groove in the other vertical edge. Accordingly, adjoining components 14, illustrated in FIG. 9, are interengaged by introducing the tongue 82 from one of the components into the groove 84 of the adjoining component. This interlocks adjacent foundation components. An adhesive may be introduced between the tongue and groove interconnection to enhance the interconnection.
 As shown in FIG. 1, corner foundation component 20 interconnects two lengths of adjoining foundation components 14 at a 90° angle. Other non perpendicular angles may be utilized. Component 20 is shown alone in FIG. 10. That component actually comprises a pair of individually pre-cast components 90 and 14 a that are joined in the manner described below. It should be noted that component 14 a features a construction that is analogous to the previously described linear foundation components 14. FIG. 10 shows component 14 a looking down on upper edge 72. The ledge 74 that projects from the inside surface of component 14 a is also clearly visible. A groove 84 is formed in one vertical end and a tongue 82 is formed on the opposite vertical end of component 14 a.
 Corner component 20 also includes an elongate piece 90. This piece is modified somewhat from the previously described foundation pieces. In particular, piece 90 includes a vertical groove 84 a formed in one side edge thereof. However, piece 90 does not include a tongue at its opposite edge. A receptacle 80 a having a generally inverted T-shaped configuration extends form the base of groove 84 a to the opposite end of component 90. A ledge 74 a is formed on the inside surface of component 90 a. Ledge 74 a does not extend for the entire length of component 90. Rather, it terminates a distance from the vertical edge of piece 90 opposite the edge in which groove 84 a is formed. As a result a recess 93 is formed proximate one end of component 90. The distance that the ledge terminates is approximately equal to the thickness of piece 20. A transverse, tapered tongue 94 extends from piece 90 into recess 93. As best shown in FIG. 10, components 14 a and 90 are interengaged to form an angle of 90°. In particular, one end of piece 14 a fits into recess 93 at the end of piece 90. Tongue 94 of piece 90 fits into groove 84 of piece 14 a in a generally mating fashion. As a result, pieces 14 a and 90 form an angle of 90°. Once again, an appropriate adhesive may be introduced between groove 84 and tongue 94. The distal end of piece 14 a carries a vertical tongue 82 that fits into a complementary groove formed in an adjoining foundation component 14. Similarly, groove 84 a formed in piece 90 receives the tongue of an adjoining foundation component. In this manner, two lengths of interconnected foundation components may be joined at the corner of the building by corner component 20.
 As shown in FIGS. 1 and 2, exterior wall component 16 is mounted upon foundation component 14 such that lower edge 100 of component 16 directly inter-engages upper edge 72 of component 14. As shown in FIG. 1, at least some of the exterior wall components 16 may include windows W or other standard features formed therein.
 A representative component 16 is shown by itself in FIGS. 11 and 12. In particular, this component includes a panel 102 that has a generally rectangular configuration. The panel includes opposing lower and upper edges 100 and 104, respectively. As illustrated in FIGS. 1 and 2, a relatively thick portion 106 may protrude from the outer face of each exterior wall component proximate upper edge 104. Such a protrusion is not depicted in FIGS. 11 and 12.
 Each wall component 16 includes a lower receptacle 108 that is formed longitudinally in lower edge 100. As best shown in FIGS. 2 and 12, receptacle 108 has a generally “T” shaped cross sectional configuration that is identical or closely analogous to the shape of receptacle 80 in upper edge 72 of foundation component 14. Once again, receptacle 108 may comprise a void or opening or, more typically, may include a steel or synthetic insert. Receptacles 108 and 80 abut in the manner best shown in FIG. 2 such that they are generally opposed to and aligned with one another. In this condition, the aligned receptacles 80 and 108 slidably receive a connector element that comprises a “Z” shaped bar 110. This Z-shaped bar fits in the aligned receptacles such that foundation component 14 and wall component 16 are interlocked with one another and prevent it from separating. As a result, the wall components are securely connected to the underlying foundation components. Receptacles and connector pieces having differing configurations may also be used within the scope of this invention.
 An additional receptacle 112, FIGS. 2 and 12, is formed in upper edge 104 of wall component 16. Receptacle 112 is typically constructed in a manner identical or similar to the previously described receptacles. In this case, receptacle 112 comprises an inverted “T” shaped cross sectional configuration. The receptacle extends longitudinally through the upper edge of the wall component. A standard roof truss tie 114 features an L-shaped configuration including a foot 116 that fits within the base 118 of receptacle 112. The vertical portion 120 of tie 114 likewise fits slidably within the vertical portion 122 of receptacle 112. The receptacle at the top of wall component 16 allows standard truss ties 114 to be slid into position as shown in FIG. 1. In this manner, the roof of the structure may be mounted to the assembled exterior wall components. The truss ties may be located quickly and conveniently even by unskilled workers. If the positioning is initially incorrect, the truss ties may be quickly repositioned by simply sliding them through the upper receptacles 112 into their proper positions.
 Each wall component 16 carries a longitudinal tongue 124 along one vertical side thereof. A longitudinal groove 126 is formed in the opposite vertical edge of the exterior wall component. The tongue and the groove have complementary tapered cross sectional shapes similar to those previously described for the tongue and groove formed in the foundation component. Adjoining wall components 16 are interlocked by simply inserting the tongue 124 from one of the wall components into the groove 126 of the adjoining wall component. The adjoining wall components thereby abut in an aligned manner analogous to that previously described for the foundation components shown in FIG. 9.
FIG. 1 depicts a representative corner wall component 22, which contains a door D. It should be noted that doors and/or windows may be formed in one or more of the wall components 16, as well as in the corner wall component 22. Corner component 22 is shown by itself in FIG. 13. In this version, the component comprises a single unitary piece although, alternatively, multiple pieces may be featured. More particularly, component 22 includes a pair of wall panels 130 and 132 that are pre-cast or molded together at an angle of 90° or at other, non-perpendicular angles. As a result, component 22 has a generally L-shaped cross sectional configuration best shown in FIG. 13. A pair of longitudinal upper receptacles 112 a, which are analogous to the previously described receptacle 112, are formed within the upper surface 104 a of component 22. One of the receptacles 112 a extends longitudinally through panel 130 and the other receptacle 112 a extends longitudinally through panel 132. The receptacles 112 a intersect and form an angle of 90° that intersect at point 140 and define an angle of 90°. The distal vertical end of panel 130 includes a groove 126 a and the distal end of panel 132 similarly includes a tapered tongue 124 a. The tongue and groove of the corner wall unit 122 have respective shapes and lengths that correspond to the tongues 124 and grooves 126 carried by the exterior wall components 16. As a result, adjoining wall components are interlocked and interengaged with corner component 22. A first wall component 16 abuts the distal end of panel 32 such that the groove 126 in component 16 receives the tongue 124 a of panel 132. Similarly, an adjoining wall panel 16 abuts the distal end of panel 130 such that the tongue of the wall component is received by groove 126 a in panel 130. When the wall components are assembled in this manner, the upper receptacles 112 in the wall components are aligned with the receptacles 112 a formed in the corner panels with which the wall components abut. A continuous linear receptacle is formed so that the truss tie downs can be freely adjusted along the length of the walls of the building.
 It should be understood that the pre-cast components described herein may have various sizes and configurations other than those shown herein. Additionally, the components may be assembled in a wide assortment of arrangements within the scope of this invention. A particular building project may utilize various numbers and types of the components described herein. The corner components may form angles other than 90°.
 The use of the above described modular building components permits a concrete building to be assembled quickly, precisely and efficiently. Few, if any, delays are encountered. The modular components may be assembled by a small crew of even unskilled or semi-skilled workers. The individuals components are manufactured at a factory rather than in the field. This improves quality control and eliminates manufacturing miscalculations and costly and time consuming construction errors. The secure, reliable interconnection between the components achieves a building of superior structural integrity. The building resists severe weather conditions and is also quite fire resistant.
 From the foregoing it may be seen that the apparatus of this invention provides for a pre-cast building system. While this detailed description has set forth particularly preferred embodiments of the apparatus of this invention, numerous modifications and variations of the structure of this invention, all within the scope of the invention, will readily occur to those skilled in the art. Accordingly, it is understood that this description is illustrative only of the principles of the invention and is not limitative thereof.
 Although specific features of the invention are shown in some of the drawings and not others, this is for convenience only, as each feature may be combined with any and all of the other features in accordance with this invention.
 Other embodiments will occur to those skilled in the art and are within the following claims: