Modular Composite Floor Units

Abstract

The invention provides a modular composite floor unit and a method for its manufacture. The floor unit is factory-made. An edge frame ( 10 ) is provided from cold-rolled sheet metal members ( 24 and 32 ) welded or brazed together to create edge shuttering. A cast concrete ceiling slab ( 12 ) is cast within the edge frame ( 10 ) over a smooth casting surface. The cast ceiling slab ( 12 ) encases a first inturned lip of the edge frame ( 10 ), a first lattice ( 26 ) of reinforcing rods or wires anchored at their ends to opposite sides and ends of the edge frame ( 10 ), and the bottom edges, or hangers ( 70 ) suspended below the bottom edges, of an array of mutually parallel spaced metal joists ( 18 ) which are welded or brazed to the edge frame ( 10 ) at their opposite ends. An infill layer is then created from blocks ( 16 ) or particulate material filling most of the height of the exposed portions of the array of mutually parallel spaced joists ( 18 ). A concrete floor slab ( 14 ) is cast within the edge frame ( 10 ) over the top of the infill layer, encasing an upper inturned lip of the edge frame ( 10 ), a second lattice ( 28 ) of reinforcing rods or wires anchored at their ends to opposite sides and ends of the edge frame ( 10 ), and the top edges, or anchorage members ( 60 ) secured to the top edges, of the mutually parallel spaced joists ( 18 ). The top surface of the cast floor slab ( 14 ) is float-finished to create a final floor unit that requires no screeding. The bottom surface of the cast ceiling slab ( 12 ) has a finish defined by the surface on which it was cast, and is visible without further treatment as the ceiling of the room below the floor unit when the unit is used in the construction of a multi-storey building.

1 . A modular composite floor unit for an above-ground-level floor of a building, comprising:
 an edge frame made from cold-rolled sheet metal edge members welded or brazed together to form an accurately sized and proportioned edge shuttering for the floor unit:   a cast cement-based or gypsum-based ceiling slab cast within the edge frame and encasing a first lattice of reinforcing rods or wires; and   a cast cement-based flooring slab spaced from the ceiling slab and cast within the edge frame, encasing a second lattice of reinforcing rods or wires which are welded or brazed at their ends to opposite edge members of the edge frame;   each of the ceiling and flooring slabs being supported across its width by an array of mutually parallel spaced metal joists which extend across the floor unit between the cast slabs and are welded or brazed at their opposite ends to opposite edge members of the edge frame; and   the space between the ceiling and flooring slabs containing a sound insulating material of lower density than that of the cast ceiling and floor slabs.   
   
   
       2 . A floor unit according to  claim 1 , wherein the sound insulating material completely or substantially completely fills the inter-joist space between the cast ceiling and floor slabs. 
   
   
       3 . A floor unit according to  claim 2 , wherein the sound insulating material comprises an array of blocks of lower density than that of the material of the cast ceiling and floor slabs. 
   
   
       4 . A floor unit according to  claim 3 , wherein the blocks are blocks of a cinder-based or porous aggregate-based cement walling block material, expanded polystyrene, rockwool, compressed straw or balsa wood; or are plastic or cardboard boxes filled with loose particulate material such as rockwool, shredded newspaper, paper mache, chopped straw, glass fibre matting or reclaimed particulate rubber. 
   
   
       5 . A floor unit according to  claim 3 , wherein the cast floor slab has been cast directly over the tops of the array of blocks and has been allowed to flow around and between the blocks of the array. 
   
   
       6 . A floor unit according to  claim 2 , wherein the sound-insulating material comprises a layer of a lightweight sound absorbing material laid over the top of the cast ceiling slab and between the joists, and a solid board or an array of solid boards placed over the sound absorbing material, the board or boards being supported by the sound absorbing material or by the joists. 
   
   
       7 . A floor unit according to  claim 6 , wherein the cast floor slab has been cast over the top of the solid board or boards. 
   
   
       8 . A floor unit according to  claim 1 , wherein the sound insulating material only partially fills the space between the cast ceiling and floor slabs. 
   
   
       9 . A floor unit according to  claim 8 , wherein the sound insulating material comprises a layer of lightweight sound absorbing material laid over the top of the cast ceiling slab and between the joists, and a solid board or an array of solid boards supported by the joists at a level spaced from the top of the layer of sound-absorbing material. 
   
   
       10 . A floor unit according to  claim 9 , wherein the cast floor slab has been cast over the top of the solid board or boards. 
   
   
       11 . A floor unit according to  claim 1 , wherein each joist has one longitudinal edge embedded in the material of the cast ceiling slab and an opposite longitudinal edge embedded in the material of the cast floor slab. 
   
   
       12 . A floor unit according to  claim 11 , wherein the joists are made from cold-rolled C-section steel. 
   
   
       13 . A floor unit according to  claim 1 , wherein each joist has one longitudinal edge embedded in the material of one of the cast slabs and an opposite longitudinal edge in the space between the cast slabs, in an alternating sequence of joists or pairs of joists across the floor unit. 
   
   
       14 . A floor unit according to  claim 13 , wherein the joists are made from cold-rolled J-section steel, the inturned longitudinal edge of each section being that which is located in the space between the cast slabs. 
   
   
       15 . A floor unit according to  claim 13 , wherein the joists having a longitudinal edge embedded in the material of the cast ceiling slab are offset laterally from those having a longitudinal edge embedded in the material of the cast floor slab, the wall portions of the respective joists extending more than half way across the space between the cast ceiling and floor slabs. 
   
   
       16 . A floor unit according to  claim 15 , wherein pairs of adjacent joists, one having an edge embedded in the material of the cast ceiling slab and the other having an edge embedded in the material of the cast floor slab, are closely adjacent one another and separated by a greater distance from adjacent similar pairs of joists. 
   
   
       17 . A floor unit according to  claim 16 , wherein free edges of adjacent joists having edges embedded in the material of the same cast slab, those free edges being the edges located in the space between the slabs, are joined together at intervals along the length of the joists by straps which transfer buckling loads between the joists. 
   
   
       18 . A floor unit according to  claim 10 , wherein the joists are hollow box section joists or hot rolled parallel flanged channel joists. 
   
   
       19 . A floor unit according to  claim 18 , wherein the cast ceiling slab is supported by the joists across its width by hangers suspended from the joists or from some of the joists and supporting the first lattice of reinforcing rods or wires across the width of the cast ceiling slab. 
   
   
       20 . A floor unit according to  claim 19 , wherein the hangers are wire hangers. 
   
   
       21 . A floor unit according to  claim 19 , wherein the hangers are metal straps which pass over the joists from which they are suspended and hang down on opposite sides of those joists, having transverse slots in lower ends of the hangers which hook around and support the reinforcing rods or wires of the first lattice. 
   
   
       22 . A floor unit according to  claim 18 , wherein the cast floor slab is supported by the joists across its width by being cast on a solid board resting directly on the top of those joists. 
   
   
       23 . A floor unit according to  claim 22 , wherein the cast floor slab is anchored to the joists which support it across its width by an array of anchorage members which are connected to the second lattice of supporting rods or wires and are screwed to the joists which support the cast floor slab through the solid board. 
   
   
       24 . A floor unit according to  claim 23 , wherein each of the box section joists supports both the cast ceiling and floor slabs. 
   
   
       25 . A floor unit according to  claim 23 , wherein alternate ones of the box section joists across the width of the floor unit support the cast ceiling slab and intermediate ones of the box section joists support the cast floor slab. 
   
   
       26 . A floor unit according to  claim 18 , wherein the box section joists contain a sound-absorbing material. 
   
   
       27 . A floor unit according to  claim 10 , wherein embedded in the cast ceiling slab and/or the cast floor slab are reinforcing diagonal cross-struts welded at their ends to the edge frame. 
   
   
       28 . A floor unit according to  claim 27 , wherein the reinforcing diagonal cross-struts are made from ribbons of sheet metal that have been unrolled from a roll and prevented from curling by imparting a longitudinal crease thereto. 
   
   
       29 . A floor unit according to  claim 10 , wherein each of the cast ceiling and floor slabs has a thickness of from 50 to 100 mm, and the space between the cast ceiling and floor slabs is from 150 to 300 mm. 
   
   
       30 . A floor unit according to  claim 29 , wherein each of the cast ceiling and floor slabs has a thickness of about 65 mm. 
   
   
       31 . A floor unit according to  claim 29 , wherein the space between the cast ceiling and floor slabs is about 225 mm. 
   
   
       32 . A floor unit according to  claim 10 , wherein the surface finish of the underside of the cast ceiling slab is a paper or fabric material that has been laid over the casting surface on which the ceiling slab has been cast. 
   
   
       33 . A floor unit according to  claim 10 , wherein the surface finish of the underside of the cast ceiling slab is the surface finish of a board or plate that has been covered with a mould release agent before casting the ceiling slab. 
   
   
       34 . A floor unit according to  claim 10 , wherein the surface finish of the top surface of the cast ceiling slab is a power float finish. 
   
   
       35 . A method for the manufacture of a floor unit, which comprises:
 forming an edge frame by welding or brazing together cold-rolled sheet metal edge members;   welding or brazing to the edge frame an array of mutually parallel spaced metal joists;   welding or brazing to the edge frame the ends of the reinforcing rods or wires of the first lattice;   casting the ceiling slab by pouring wet concrete or gypsum-based plaster into the shuttering created by the edge frame, to a depth sufficient to encase a first inturned lip of the edge frame, to encase the first lattice of reinforcing rods or wires, and to embed lower longitudinal edges of some or all of the parallel spaced joists of cold-rolled sheet metal or of hangers suspended from those joists;   placing between the parallel spaced joists of cold-rolled sheet metal the sound insulating material of lower density than the concrete of the cast slabs and optionally the array of solid boards to form a base for the cast ceiling slab;   welding or brazing to the edge frame the ends of the reinforcing rods or wires of the second lattice;   pouring wet concrete over the top layer of sound insulating material or over the tops of the solid boards to a depth sufficient to encase a second inturned lip of the edge frame, to encase the second lattice of reinforcing rods or wires and optionally to embed upper longitudinal edges of some or all of the parallel spaced joists of cold-rolled sheet metal; and   providing a smooth surface finish to the top of the cast floor slab using a power float.