Stair system with expandable center

Abstract

A staircase assembly comprising a plurality of stringers, and; a plurality of stair units, having treads and risers wherein stair unit is secured by means of fastening means on each corner to said plurality of stringers, said stringers, having a diagonally shaped series of equally spaced substantially vertical structure notched out of one side to define the length and height of each step of the stair assembly. The said tread,-forming a channel by rolling the leading edge for holding the riser of the stair unit installed immediately below, and each stair unit is secured by means of fastening means on each corner to said plurality of stringers, said channels further engaging other stair unit laterally sliding for providing horizontal adjustability.

1 . A staircase assembly comprising: 
 a plurality of stringers having a diagonally shaped series of equally spaced substantially vertical structure notched out of one side to define the length and height of each step of the stair system; and    a plurality of stair units, having treads and risers wherein said tread forming a channel by rolling the leading edge for holding the riser of the stair unit installed immediately below, and each stair unit is secured by means of fastening means on each corner to said plurality of stringers, said channels further engaging other stair unit laterally sliding for providing horizontal adjustability.    
   
   
       2 . A staircase assembly as define in  claim 1  wherein said assembly further comprising treat having catching holes at a predetermined distance of the staircase system and a handrail assembly having a handrail posts, securing means, and rails, handrail post designed for fixing to the holder of said stringers through the catching holes of said treads and securing means are configured for clamping this assembly tightly to said stringers.  
   
   
       3 . A staircase assembly as defined in  claim 1 , wherein said stringer further comprising holders at first predetermined distance holder is cylindrical in shape and is open from the top to lock the handrail post in place.  
   
   
       4 . A staircase assembly as defined in  claim 1 , wherein said first predetermined distance is identified according to the length of the staircase.  
   
   
       5 . A staircase assembly as defined in  claim 1 , wherein said riser having a jutting projection for holding said tread of immediate upper stair unit.  
   
   
       6 . An adjustable staircase assembly system comprising: 
 a plurality of stairs each stair having a riser having a receiving grove at its angled corner, and; a tread having a first projecting structure, a curved structure and a second projecting structure, for fixing on top of said base unit wherein said first projecting structure is configured for fixing it into the said receiving grove of the base unit, and the curved structure is configured for clamping the said second projecting structure of a second stair to form a staircase assembly.    
   
   
       7 . An adjustable staircase assembly as defined in  claim 6 , wherein said assembly further comprising an adjustable central support frame for supporting stairs.  
   
   
       8 . An adjustable staircase system as defined in  claim 6 , wherein said assembly may optionally be provided with a railing.  
   
   
       9 . A method of constructing adjustable stairs between a floor and a deck, comprising the steps of: 
 measuring a distance the floor and the deck located above the floor;    cutting stringers in accordance with information gathered in said measuring step,    forming treads and risers to substantially securely mate with said stringers to produce a finished stair unit; and    securing said finished stair unit to the floor and the deck.