Method and apparatus for lifting, leveling, amd underpinning a building foundation

Abstract

A method and apparatus for leveling a building foundation including excavating a cavity below the portion of the foundation to be raised at regular intervals and using and an oversized screw anchor driven under the foundation at approximately 15 degrees relative to the foundation edge at each of the excavated cavities, the anchor having relatively large helical screw flighting or auger plate to insure support at relatively shallow depths. Each excavated cavity is provided with a bed of dry cement mix. The method includes the steps of installing an anchor jack-plate upon said bed of dry cement the jack plate having a collar and gusset attached thereto slidable upon the screw anchor shaft, providing a pair of hydraulic jacks atop the anchor plate, taking a portion of the foundation load on each jack, thereby directing the load at each jack in axial alignment with the helical screw anchor flighting or auger plate, setting the cement by wetting and welding the collar of the anchor jack-plate to the screw anchor shaft only when the foundation is considered level, installing a screw jack at each lifting point and removing the hydraulic jacks and pumping cement into any voids detected below the foundation footing.

What is claimed is:  
     
         1 . A foundation underpinning apparatus comprising: 
 a) a screw anchor assembly having an extendable shaft portion and an auger blade portion; and    b) a first base plate assembly comprising: 
 i) a base plate;  
 ii) a tubular collar slidable upon said shaft portion attached perpendicular to one edge of said first base plate; and  
 iii) a gusset plate attached perpendicular to said first base plate and said tubular collar.  
   
     
     
         2 . The foundation underpinning apparatus according to  claim 1  wherein said collar is attached to said base plate and said gusset at an approximate angle of 15 degrees.  
     
     
         3 . The foundation underpinning apparatus according to  claim 1  wherein said auger blade portion is between 18- and 24 inches in diameter.  
     
     
         4 . The foundation underpinning apparatus according to  claim 1  wherein said apparatus further comprises a second base plate placed parallel and in contact with said first base plate.  
     
     
         5 . A method for lifting and underpinning a building foundation comprising the steps of: 
 a) excavating at least one cavity below the perimeter of a building foundation;    b) inserting a screw anchor having an extendable shaft portion and an auger portion at an angle of approximately 15 degrees relative to the outer vertical edge of the building foundation to a sufficient depth to insure stability and extending said anchor as necessary to reach the surface of the foundation;    c) filling at least a portion of said cavity with dry cement mix forming a bed therein;    d) providing and installing a first base plate assembly comprising a base plate, a tubular collar, slidable upon said shaft portion, attached perpendicular to one edge of said first base plate; and a gusset plate attached perpendicular to said first base plate and said tubular collar at vertical angle of approximately 15 degrees and in such a manner that said gusset plate is pressed into said cement mix and said base plate rests on the surface of said bed;    e) providing a second base plate parallel to and in contact with said first base plate;    f) installing at least one hydraulic jack vertically between said second base plate and said foundation;    g) actuating said hydraulic jack; thereby lifting said foundation to near level plane;    h) providing and installing a screw jack adjacent said hydraulic jack and adjusting said screw jack to take the full load of said hydraulic jack and removing said hydraulic jack;    i) wetting said cement mix sufficiently to form a cement pier; and    j) welding said collar to said screw anchor and removing any excess portion of said shaft.    
     
     
         6 . The method according to  claim 5  further comprising the step of placing said screw jack in a manner whereby the vertical axis of said screw jack is aligned with the vertical central axis of the shaft of said screw anchor and the vertical axis of said screw jack crosses the vertical axis of said shaft at the approximate location of said auger portion.  
     
     
         7 . The method according to  claim 5  wherein the load of said foundation is divided between said cement pier and said screw anchor.