Method and apparatus for production of precision precast concrete flights of stairs

A method for forming a precision precast concrete flight of stairs to provide access between vertically spaced apart levels of a structure, the method comprising the steps:

• determining a substantially exact vertical distance between a predetermined lower level landing position and a predetermined vertically adjacent upper level landing position;
• determining a substantially exact horizontal distance between the predetermined lower level landing position and the predetermined vertically adjacent upper level landing position;
• calculating a number of equally dimensioned stair risers and a number of equally dimensioned stair treads to span the substantially exact vertical distance and the substantially exact horizontal distance between the lower level landing position and the vertically adjacent upper level landing position while maintaining the stair treads and the upper level landing and the lower level landing in substantially parallel orientation relative to one another;
• precision cutting form components, for forming the precision precast concrete flight of stairs, and precision drilling holes therein at predetermined positions to facilitate assembly and disassembly of the precision cut form, the precision cut form components comprising sideboards, tread supports, stair risers, stair treads, upper landing end plates, lower landing end plates, upper landing end caps, lower landing end caps, upper landing treads, lower landing treads, center tread support spacers, alignment tabs and end plate locks;
• interconnecting the tread supports to the sideboards;
• assembling the stair risers and the stair treads by interconnecting each stair riser with a stair tread along adjacent edge portions with a stair tread edge overlapping a stair riser edge;
• assembling a center tread support assembly from plural tread supports and positioning and interconnecting plural center tread support spacers between the plural tread supports so that the center tread support spacers extend transversely between the plural tread supports;
• assembling an upper landing assembly with the upper landing tread, the upper landing end plate and a stair riser and attaching an alignment tab to a bottom surface of the upper landing tread for aligning and squaring the upper landing assembly within the assembled center tread support;
• assembling a lower landing assembly with the lower landing tread and the lower landing end plate and attaching an alignment tab to a bottom surface of the lower landing tread for aligning and squaring the lower landing assembly within the assembled center tread support;
• positioning the assembled center tread support assembly on a horizontal supporting surface and positioning the assembled upper landing assembly within the assembled center tread support assembly, at an upper end portion thereof, and engaging the alignment tab carried on the bottom surface of the upper landing tread within the assembled center tread support assembly to square and align the upper landing assembly within the assembled center tread support;
• positioning the assembled stair risers and stair treads within the assembled center tread support beginning immediately adjacent the positioned upper landing assembly and continuing the positioning of the assembled stair risers and stair treads to an end of the assembled center tread support opposite the positioned upper landing assembly;
• positioning the assembled lower landing assembly within the assembled center tread support assembly, at the end apposite the upper landing assembly and engaging the alignment tab carried on the bottom surface of the lower landing tread within the assembled center tread support assembly to square and align the treads, risers and landing assemblies with the center tread support;
• positioning and interconnecting with fasteners the sideboards to each side of the upper landing assembly, the stair risers and stair treads and the lower landing assembly positioned within the center tread support assembly, the fasteners extending through the precision drilled holes;
• positioning, aligning and interconnecting with fasteners an upper end plate cap adjacent the upper landing assembly, the upper end plate cap extending transversely between the spaced apart side boards and interconnecting with an upper landing toe carried on each side board;
• positioning, aligning and interconnecting with fasteners a lower end plate cap adjacent the lower landing assembly, the lower end plate cap extending transversely between the spaced apart side boards and interconnecting with a landing slant bottom defined in each side board at an end portion opposite the upper landing assembly;
• positioning and interconnecting with fasteners an end plate lock on each sideboard immediately adjacent the lower landing end plate and immediately adjacent the upper landing end plate to positionally secure the landing end plates relative to the sideboards;
• adding reinforcing rebar members within the assembled form to provide structural rigidity to the precision precast concrete flight of stairs;
• adding flowable concrete into the assembled form, and allowing the flowable concrete to cure/harden;
• removing the end plates and the end plate caps and removing the sideboards from the hardened precast concrete flight of stairs by removing the fasteners;
• removing the cured/hardened precision precast concrete flight of stairs;
• and
• reassembling and reusing the precision cut stair form for another precision precast concrete flight of stairs.

A precision cut form for precision forming a concrete stringer of stairs to provide access between vertically spaced apart levels of a structure, the precision cut form comprising:

• plural tread supports, each tread support having a first side and a second side, a first end and a second end, a bottom edge and a top edge, the top edge defining a plurality of intersecting tread cutouts and riser cutouts forming interior angles and exterior angles between the intersecting tread cutouts and riser cutouts and the first and second sides each defining plural spacedly arrayed alignment dowel holes;
• plural sideboards, each sideboard having a first side and a second side, a first end and a second end, a top edge, a bottom edge and a surface coating on at least one side, the surface coating to provide a desired final surface texture to the concrete stringer of stairs, each side board defining a plurality of precision located spacedly arrayed fastener holes, and each sideboard further carrying a tread support on the surface coated surface;
• plural stair risers, each stair riser having a front surface and a back surface, a top edge and a bottom edge, a first end and a second end and a surface coating on at least one surface, the surface coating to provide a desired final surface texture to the concrete stringer of stairs, the top edge and the bottom edge having a precision cut angle thereon to provide for a riser back-set relative to an adjacent stair tread, and a height dimension between the top edge and the bottom edge that is substantially identical for all of the plurality of stair risers;
• plural stair treads, each stair tread having a top surface and a bottom surface, a first end and a second end, a toe edge and a heel edge and a surface coating on at least one surface, the surface coating to provide a desired final surface texture to the concrete stringer of stairs, the toe edge of each stair tread interconnected with the top edge of a stair riser to form a stair tread and stair riser combination having an interior angle between the stair tread and the stair riser that provides for the back set, and a tread depth dimension between the toe edge and the heel edge that is substantially identical for all of the plural stair treads;
• an upper landing end plate communicating between two spaced apart side boards proximate the second end portion, the upper landing end plate having a first side and a second side, a first end portion and a second end portion, a top edge and a bottom edge, the upper landing end plate further defining plural spacedly arrayed rebar holes therein communicating between the first side and the second side for reinforcing rebar to be spacedly positioned within the precision cut form to add structural rigidity to the produced concrete flight of stairs;
• lower landing end plate communicating between two spaced apart side boards proximate the first end portion, the lower landing end plate having a first side and a second side, a first end portion and a second end portion, a top edge and a bottom edge, the lower landing end plate further defining plural spacedly arrayed rebar holes therein communicating between the first side and the second side for reinforcing rebar to be spacedly positioned within the precision cut form to add structural rigidity to the produced concrete flight of stairs;
• an upper landing end plate cap having a top edge and a bottom edge, a first surface and a second surface, a first edge and a second edge, the upper landing end plate cap communicating between upper landing toes carried on the top edge of the spaced apart sideboards spacedly adjacent the second end portion of the side boards;
• a lower landing end plate cap having a top edge and a bottom edge, a top surface and a bottom surface, a first edge and a second edge, the lower landing end plate cap communicating between landing slant bottoms defined in the first end portions of the side boards to form a bottom surface of a lower landing of the concrete flight of stairs;
• an upper landing tread having a top surface, a bottom surface, a first edge, a second edge, a first side and a second side, and precision predrilled holes therein, the upper landing tread communicating between the two spaced apart side boards to form an upper landing of the concrete stringer of stairs;
• a lower landing tread having a top surface, a bottom surface, a first edge, a second edge, a first side and a second side, and precision predrilled holes therein, the lower landing tread communicating between the two spaced apart side boards to form a lower landing of the concrete stringer of stairs;
• plural center tread support spacers for positioning between two parallel spaced apart tread supports to form a center tread support, each of the plural center tread support spacers having a first side, a second side, a top edge, a bottom edge, a first end, a second end and having a width dimension between the first end and the second end, the first end and the second end each defining plural spacedly arrayed alignment dowel holes to carry alignment dowels therein to facilitate interconnection with a tread support;
• plural alignment tabs for predetermined positioning on the bottom surface of the lower landing tread and the bottom surface of the upper landing tread to facilitate automatic squaring and alignment of the precision cut form, each alignment tab having a first side, a second side, a top edge, a bottom edge, a first end, a second end and a width dimension between the first end and the second end that is substantially identical to the width dimension of the plural center tread support spacers;
• end plate locks for releasable attachment to the side boards immediately adjacent the upper landing end plate and immediately adjacent the lower landing end plate to positionally secure the upper landing end plate and the lower landing end plate in a predetermined position relative to the adjacent side boards;
• and
• splice boards for releasably interconnecting adjacent side boards and adjacent tread supports.