Abstract:
A prefabricated foundation is provided using a plurality of concrete panels that are cast at a factory location to a predetermined uniform form and size. These panels are of a generally rectangular shape and are positioned end to end forming a wall-like structure around the entire perimeter of a prefabricated structure. The lower surface of the panels are then supported by a plurality of precast posts that correspond in position and number to the joints between the plurality of panels. The joint between two abutting precast panels is sealed to provide a weather tight fit between the exterior and interior of the panels. The upper edge of the precast panels are locked in position keeping them from moving in either an inward or outward manner thereby providing a stable platform upon which a prefabricated structure can be placed.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an improvement in the foundation system used on prefabricated structures, such as mobile homes or factory manufactured buildings. More specifically, a foundation system made of a plurality of precast panels that rest on precast posts and not only support the panels but also close in the space between the lower surface of the structure in a manner that is both weather tight and aesthetically pleasing. 
   In the past, prefabricated structures were positioned at their building sites by the use of a poured concrete slab or conventional concrete footings. The use of these foundation systems created two separate problems. The first of these is that they are relatively labor and material intensive resulting in higher costs that to some degree offset the cost saving advantages that are inherent in the factory built methods of constructing housing or other buildings. 
   Secondly, these types of foundation systems require an additional mechanism to close off the open space between the bottom surface of the structure&#39;s rim joist and the surface of the ground. Typically, this space is closed off by the use of wood, vinyl or sheet metal skirting material. The use of these materials is undesirable because they form a barrier that is insecure and that requires a great deal of maintenance to keep it in a good state of repair. Additionally, the use of such construction materials does not provide a weather tight structure that is often necessary in such structures, especially when they are placed in northern areas where there is a need to provide an insulated space between the structure and the surface of the ground. Finally, the use of these materials results in a finished appearance that clearly indicates that it is a prefabricated structure instead of site-built which is an undesirable result to the eventual owner. 
   The prior art has examples of attempts to resolve these problems. The first of these is illustrated in U.S. Pat. No. 5,067,289 issued to Ouderkirk which provides a unified wooden foundation and skirting system for these types of structures. The most obvious problems with this solution is that the use of wood for this purpose is that it results in a foundation system that lacks in structural integrity and which is susceptible to durability problems associated with weathering and material rot. Additionally, this foundation system requires the use of a plurality of foundation units being placed in the center area of the structure for further support. This adds a degree of difficulty to the operation as it requires that all of these additional structural components be placed in a manner so that they are all exactly level in relation to themselves and the remaining components of the foundation. 
   A further solution to this problem is offered in U.S. Pat. No. 6,125,597 issued to Hoffman which provides a foundation and skirting system that employs a plurality of precast concrete panels resting on footing blocks positioned in the ground. The precast panels provide both the foundation and skirting for the prefabricated structure and the blocks are secured in position by the use of anchor rods that extend through them and down into the ground. The problem with this solution is that the placement of the blocks requires the builder dig a trench and prepare that exposed surface in a manner that will adequately support the blocks and the weight of the structure that they carry. This method of construction can result is a susceptibility to settling due to inconsistent ground conditions and types. Additionally, it does not provide a mechanism by which the foundation can compensate for frost heaving conditions that are common in colder climates. Finally, the provided anchoring system for the footing blocks is not secure enough when considering the loads that they must carry during the course of the structure&#39;s life. 
   Therefore, it can be seen that it would be desirable to provide a method of securing a prefabricated structure to a building site that takes advantage of the cost effective nature of such buildings in a manner that not only effectively secures the structure in place but also closes off the area between the bottom of the structure on the surface of the earth. Additionally, it would be desirable to provide a means of closing off this area in a manner that results in an insulated interior space and which results in a finished structure that adds to the aesthetic value of the structure by providing an end product that closely mimics the look of a site built unit. 
   SUMMARY OF THE INVENTION 
   It is the primary objective of the present invention to provide a precast foundation system specially designed for prefabricated housing which not only serves to secure the home to the earth but also to enclose their lower structural elements in a weather tight and attractive manner. 
   It is an additional objective of the present invention to provide such a precast foundation system that does not require that the builder construct concrete footings around the entire perimeter of the prefabricated house which has the effect of reducing building costs through the elimination of excess time and materials in the construction process. 
   It is a further objective of the present invention to provide such a precast foundation system that is composed of precast concrete panels and posts that can be assembled into their final configuration on site in an efficient and timely manner that will further reduce construction costs by standardizing the materials and methods used in the building of such structures. 
   It is a still further objective of the present invention to employ such a precast foundation system having external walls that are cast with decorative construction material patterns, such as mimicking brick or natural stone, thereby adding aesthetic value to the structure without incurring the greatly increased construction costs associated with the actual use of these materials. 
   These objectives are accomplished by the use of a plurality of concrete panels that are cast at a factory location to a predetermined uniform form and size before their transport to a building site. These panels are of a generally rectangular shape and are positioned end to end in a vertical fashion with their shorter sides forming the vertical component of the rectangle. This positioning of the panels forms a wall-like structure around the entire perimeter of a prefabricated structure in a position that corresponds to the location of the rim joist (the external frame of the structure upon which its remaining components are built) of the structure. The lower surface of the panels are then supported by a plurality of precast posts that correspond in position and number to the joints between the plurality of panels. Additionally, these precast posts are positioned in a manner so that the joint between two abutting panels falls at the midpoint of the upper surface of the post. This positioning of the posts relative to the panels ensures that each end of the panels has a solid point of contact through which it can transfer the load of the structure through the post to the earth. 
   The precast posts are anchored to the earth through the use of a corresponding number of vertical holes evacuated from the ground in a line that matches the outer dimension of the structure and its rim joist. Prior to the precast posts being positioned within the holes, the lowest section of each hole is filled with uncured concrete, or similar material, to form a solid base upon which the post will rest. The concrete forms perfectly to the contours of the inner surface of the hole which effectively transfers the load carried by the posts to the earth by broadening its foot print ensuring that the lower portion of the post will not sink further into the earth than it was designed to. Therefore, the use of the precast posts and their respective concrete bases forms a solid base upon which the panels of the present invention are placed to in turn provide a solid platform upon which the structure is placed. Additionally, the design of the present invention and its major components is resistant to frost heaving and settling ensuring that the structure and its horizontal and vertical surfaces that it supports will remain plum and square, thereby extending its useful life. 
   The joint between two abutting precast panels is sealed to provide a weather tight fit between the exterior and interior of the panels. This seal is accomplished through the use of a strip of panel joint seal which is a length of compressible foam that is placed between the precast panels prior to their being placed on the precast posts. As the precast panels are forced into their final position, the panel joint seal is squeezed between the two and forms an air tight seal within the joint. This seal is then reenforced by the placement of a bead of all weather caulking in the joint on the outside of the panel joint seal. Thus, the use of the described sealing system ensures a weather tight seal at the joints of abutting precast panels and reduces the risk of frost damage occurring to the precast panels at their joints. Additionally, the joint between the upper surface of the precast panels and the lower surface of the rim joist is sealed with a similar material called the sill seal which is compressed between the two surfaces when the structure is placed on the positioned precast panels. 
   The precast panels are maintained in the proper vertical orientation by the use of a number of different components. The first of these is a plurality of stakes that are driven into the earth directly behind the inner surface of the precast panels at evenly spaced intervals. The purpose of these stakes is to ensure that the lower edge of the precast panels is not at any time forced inward which could result in their losing contact with the upper surface of the precast posts, a situation that could possibly result in system failure. The upper edge of the precast panels are kept from moving inward by the placement of joist angles that attach to the appropriate floor joists of the structure and extend for a short distance on either side of every panel joint in the body of the invention. Finally., the precast panels are kept from moving outward by the use of the rim joist angles which are attached to the lower surface of the rim joist and bend over the outside edge of the upper surface of the precast panel. Thus, the upper edge of the precast panels are locked between the vertical surfaces of the joist and rim joist angles which keeps them from moving in either an inward or outward manner thereby providing a stable platform upon which a prefabricated structure can be placed. 
   For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the present invention which illustrates the manner in which the precast panels of the present invention are arranged to form a foundation for a prefabricated structure. 
       FIG. 2  is a perspective view of a precast panel component of the present invention illustrating its manner of construction and the way that it interacts with the appropriate components of the prefabricated structure. 
       FIG. 3  is a side elevation view of the precast post component of the present invention illustrating the manner in which it is positioned within the hole and its connection to the lower surface of the precast panels. 
       FIG. 4  is a rear elevation view of a precast panel component of the present invention illustrating the mechanisms used to keep the panels in their proper position after installation between the precast posts and rim joist of the prefabricated structure. 
       FIG. 5  is a side elevation view of the junction between the upper portion of the precast panel and the rim joist of the prefabricated structure of the present invention illustrating the manner in which it is held in the desired location. 
       FIG. 6  is a top elevation view of the joint between two abutting precast panels of the present invention illustrating the use of panel joint seal and caulking to provide a weather tight seal between the interior and exterior of the wall formed by the connection of the panels. 
       FIG. 7  is a side elevation cut-away view of precast panel component of the present invention taken along line  3  of  FIG. 6  and illustrating the manner of construction of the precast panels. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, and more specifically to  FIG. 1  which illustrates the general configuration of the precast foundation  10  and its position relative to the prefabricated structure  12  (in the present instance illustrated as a prefabricated single family home). As illustrated, the precast panels  14  are lined up end to end to form a wall-like structure that forms an enclosing skirt that surrounds the lower perimeter of the prefabricated structure  12 . Additionally, the precast panels  14  are either end wall panels  16  or side wall panels  18 . The end and side wall panels,  16  and  18 , differ only in the fact that the end wall panels  16  can be equipped with vents  20  which provide a mechanism by which the air space beneath the prefabricated structure  12  can interact with the air on the outside. This ensures that the air contained within the space defined by the outside edge of the precast panels  14  will be maintained at the proper temperature and moisture content to avoid the structural problems associated with sharp temperature and humidity contrasts. 
   This FIGURE also illustrates the positioning of the precast posts  22  relative to the remaining components of the present invention. The precast posts  22  are the components of the present invention which provide the base upon which the precast panels  14  are placed to form a foundation for a prefabricated structure  12 . The use of the precast posts  22  allows a prefabricated structure  12  to be positioned in a stable manner without requiring that the builder pour footings prior to the placement of the prefabricated structure  12 . Therefore, the use of the present invention allows a prefabricated structure  12  to be positioned at a job sight in a manner that requires less time and materials which has the effect of dramatically reducing the costs associated with this type of construction. 
   The manner in which the precast panels  14  are constructed and the way in which they interact with specific components of the prefabricated structure  12  are further detailed in  FIG. 2 . The most prominent feature of the precast panel in this illustration is the decorative panel pattern  34  that is cast into the face of the precast panel  14  during the manufacturing process. This feature adds a degree of aesthetic value to the finished product by giving the face of the present invention a brick or stone-like appearance without incurring the great deal of added expense associated with the use of these types of natural building materials. 
   This FIGURE also illustrates the manner in which the precast panel  14  engages the pertinent components of the prefabricated structure  12  when installation is complete. The upper most surface of the precast panels  14  provides the platform upon which the rim joist  26  of the prefabricated structure  12  rests. Inside of the rim joist  26  a plurality of floor joists  28  extend perpendicularly across the interior of the prefabricated structure  12 . The ends of some of these floor joists  28  serve as the mounting point for the joist angle  30  which is employed to keep the upper surface of the precast panels  14  from falling inward after the prefabricated structure  12  has been placed in the finished position. The joist angle  30  is a relatively short section of large angle iron of which the joist angle horizontal surface  29  is placed against the lower surfaces of a pair of neighboring floor joists  28  and secured thereto. The other surface of the joist angle  30 , the joist angle vertical surface  31 , then extends downward at a right angle and in a position that is parallel to the line formed by the inner wall of the rim joist  26  and the outer butt ends of the floor joists  28 . This joist angle vertical surface  31  of the joist angle  30  limits range of possible motion for the upper surface of the precast panels  14  ensuring that they stay in the proper position relative to the rim joist  26 . Additionally, the joist angles are positioned laterally in relation to the plurality of precast panels  14  so that they extend into both bodies of two neighboring precast panels  14 . This configuration allows one joist angle  30  to secure the end of two neighboring precast panels  14  ensuring the maximum economy of use of this component of the present invention. 
   The present invention also makes use of an additional device formed from a section of angle iron called a rim joist angle  32 . The rim joist angle  32  is positioned in roughly the same location as the joist angle  30  except for the fact that the rim joist angle horizontal surface  33  is located on top of the precast panel  14  between it and the lower surface of the rim joist  26 . The rim joist angle vertical surface  35  of the rim joist angle  32  that extends at a right angle fits over the outer surface (that containing the decorative panel pattern  34 ) of the precast panels  14 . This manner of construction serves two purposes. The first of these is to help to secure the precast panels  14  in their upright position by keeping them from moving in an outward manner, therefore working in conjunction with the joist angle  30  to hold the upper portion of the precast panel  14  in the proper orientation. Secondly, the rim joist angle  32  serve to provide a spacing function which serves to provide and maintain a gap between the outer surface of the precast panels  14  and the inner surface of the house siding panels  54 . This provides a more professional looking joint between the prefabricated structure  12  and the present invention thereby enhancing the overall aesthetics of its use. 
   Finally, this FIGURE also illustrates the use of the dirt guard  24  which is another section of angle iron similar in its lateral dimension to that of the joist angle  30  but extending for the entire length of each precast panel  14 . The dirt guard  24  attaches to the lower surface of the precast panels  14  in a manner so that the dirt guard vertical surface  23  extends down past the lowest point of the precast panel  14 . With this manner of attachment, the dirt guard horizontal surface  25  extends outward from the base of the dirt guard vertical surface  23  forming a shelf-like configuration. The primary purpose of the dirt guard is to keep fill dirt and landscaping material from getting under the precast panels  14  while allowing landscape material to be pushed up over the dirt guard horizontal surface  25  to contact the outer surface of the precast panels  14 . This is an important aspect of the design of the present invention because, as illustrated in  FIG. 3 , the lowest edge of the precast panels  14  is positioned by the use of the precast posts  22  so that there is a space between it and the surface of the ground  42 . This design ensures that any frost heaving occurring in the ground  42  during cold weather will not affect the integrity of the present invention thereby ensuring that the prefabricated structure  12  will not be damaged by such natural occurrences. Additionally, this FIGURE also illustrates the manner in which the end of each precast panel  14  only occupies about one half of the upper exposed surface of the precast post  22 . This allows the ends of two neighboring precast panels  14  to be anchored on a single precast post  22 . 
     FIG. 3  also illustrates the manner in which the precast posts  22  are positioned within the post holes  46  that were dug within the ground  42  prior to the beginning of the installation of the present invention. Prior to the placement of a precast post  22 , the bottom most portion of the post hole  46  is filled to a predetermined level with one form of the many types of concrete available today. This creates a concrete foundation  44  upon which the bottom of the precast post  22  rests, the purpose of which is to dissipate the load carried by the precast post  22  into a larger part of the ground  42 . This design ensures that the precast post  22  will not settle into the ground  42  and affect the integrity of the present invention and the prefabricated structure  12  which it carries. 
   Once the precast post has been placed in the desired position, the remaining open area of the post hole  46  is filled in with fill sand  40  to ensure that it stays in the proper orientation. This fill sand  40  is left in an unpacked condition during the installation of the present invention so that the precast posts  22  can be adjusted to obtain the exact orientation that is required by the installation. Once this has been accomplished and the critical components of the present invention are in the desired location, the fill sand  40  is then packed tightly around the precast posts  22  to ensure that they do not subsequently shift their position. 
   Further features of the present invention that are employed to properly position the precast panels  14  are illustrated in  FIG. 4  which details their rear surface and the manner in which the ends of two neighboring precast panels  14  engage the upper surface of a single precast post  22 . This positioning of the precast panels  14  is illuminated by the position of the panel joints  48  which extend vertically upwards from the center of the precast posts  22  and are the junctions of the two neighboring precast panels  14 . The panel joints  48  also illustrate the manner in which the joist angles  30  span the upper outside corners of each of the precast panels  14  to hold the precast panels  14  on the proper location and their relation to the floor joists  28  and rim joist  26 . Additionally, this FIGURE also shows the location of the sill seal  50  which is used to create a weather tight seal between the upper surface of the precast panels  14  and the lower surface of the rim joist  26 . 
   Also employed to hold the precast panels  14  in the proper location are a plurality of anchor posts  36  which are essentially relatively short stakes that are driven into the ground  42  along the inner and lower edge of the precast panels  14 . These anchor posts  36  are placed in this fashion to ensure that the lower edge of the precast panels  14  cannot be forced inwards during backfilling or landscaping work. Finally, the use of panel shims  38  is illustrated to detail an additional available method of leveling and positioning the precast panels  14  during the installation process. The panel shims  38  are made of a corrosion resistant material enabling them to last for the life of the structure and are driven between the upper surface of the precast posts  22  and the lower surfaces of the precast panels  14  to adjust the height of their upper surfaces. The use of the panels shims  38  provides a method of fine tuning the final position of the precast panels  14  and, therefore, the final position of the prefabricated structure  12 . 
   The joint between the upper surface of the precast panels  14  and the rim and floor joists,  26  and  28 , is further detailed in  FIG. 5 . Specifically, the position of the joist angle  30  in relation to the floor joist  28  and the upper edge of the precast panels  14  are shown. Additionally, the way the joist angle attachment screw  52  is employed to securely fasten the joist angle  30  in place on the lower surfaces of the floor joists  28  is also clearly illustrated by this FIGURE. The sill seal  50  is sandwiched between the rim joist  26  and the precast panel  14  and which also runs under the rim joist angle  32  in the locations where it is positioned to maintain the location of the precast panels  14 . As previously stated, the sill seal  50  is the component of the present invention that provides an air and weather tight seal between the rim joist  26  and the precast panels  14  to ensure that the elements cannot affect the integrity of the interior components. 
   The positioning of the rim joist angle  32  and the use of the rim joist angle attachment screw  68  to anchor it to the bottom of the rim joist  26  is also illustrated in  FIG. 5  which clearly shows the manner in which the rim joist angle vertical surface  35  is used to restrict the movement of the precast panels  14 . Additionally, the spacing function of the rim joist angle  32  is illustrated in which the thickness of the rim joist angle vertical surface  35  is employed to keep the lower edge of the house siding panels  54  from contacting the outer surface of the precast panels  14 . This method of construction keeps moisture from collecting at this point and provides a more professional looking joint between the prefabricated structure  12  and the precast panels  14  of the present invention. 
   The manner of construction of the panel joint  48  is further illustrated in  FIG. 6  which details the position of the panel joint seal  56  between two neighboring precast panels  14 . Additionally, once the precast panels  14  have been properly positioned and the panel joint seal  56  has been compressed within the panel joint  48 , a bead of joint caulking  58  is placed on the outside of the panel joint seal  56  relative to the inner and outer surfaces of the precast panels  14  within the panel joint  48 . The use of the joint caulking  58  extends the life of the panel joint  48  by keeping the elements from acting upon the panel joint seal  56  and causing its deterioration. Thus, with the proper care, the panel joint  48  and the panel joint seal  56  will last for the useful life of the prefabricated structure  12  and the present invention. 
   The internal manner of construction of the precast panels  14  is illustrated in  FIG. 7  which is a cross-section view of a single precast panel  14  taken along line  3  of  FIG. 6 . The cross-sectional view illustrates the use of the panel frame  64  which is a thickened area of the precast panel  14  that surrounds its perimeter. The panel frame  64  provides a greater degree of strength to the precast panels  14  which is enhanced by the use of steel bar  62  running through its entirety. Additionally, the use of the insulation depression  66  is illustrated which is a relatively shallow depression in the body of the precast panel  14  relative to its interior surface and which makes room for the insertion of the insulation  60  within the body of the present invention. The use of the insulation  60  enhances the performance of the precast panels  14  as it provides a greater degree of heat retention and exclusion properties to the invention which the designer and builder can take advantage of to improve the performance of the prefabricated structure  12  when used in conjunction with the present invention. 
   Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.