WO2012000030A1

WO2012000030A1 - Pre- fabricated module for forming a staircase

Info

Publication number: WO2012000030A1
Application number: PCT/AU2011/000799
Authority: WO
Inventors: Epaminondas Katsalidis
Original assignee: Ekco Patent & Ip Holdings Pty Ltd
Priority date: 2010-07-01
Filing date: 2011-06-29
Publication date: 2012-01-05
Also published as: TW201207207A; EP2588687A1; AR082070A1; AU2011274305A1

Abstract

Described herein are formwork modules (3) that can be used to form a staircase (4), components of the formwork module(3), and a staircase formed with such modules (3). A pre-fabricated module (3) for forming a staircase (4) is described. The has a plurality of steps (4A) with treads (4C) and risers (4B) therebetween. The module (3) includes transversely extending riser members (16) for forming the risers (4B) of a plurality of steps(4A) and a floor (8) including a plurality of floor portions (8A), each forming the floor of a respective step(4A). Side portions (10) span between a riser member (16) and floor portion (8 A) along each side of the riser member(16). The riser members(16), floor portions (8A) and side portions (10) together defining a plurality of voids (15) to receive and form settable material (12) to define the treads of a plurality of steps (4A).

Description

PRE- FABRICATED MODULE FOR FORMING A STAIRCASE Field of the invention

The present invention relates generally to stairs. In various aspects the invention relates to formwork modules that can be used to form a staircase, components of the formwork module, and a staircase formed with the module.

The illustrative embodiments are described with reference to concrete, although it will be appreciated that other settable materials might be used to form a staircase using the formwork modules described herein. In particular it will be appreciated that formwork for forming concrete may well be used to form other materials. Background of the invention

Concrete building elements are constructed using formwork to create a temporary or permanent cast into which the concrete that is used to form the structure of the building is poured. Temporary formwork is removed after curing of the concrete, whilst permanent formwork remains as part of the structure of the building after the concrete has cured. Current methods of providing concrete formwork are very labour intensive and potentially dangerous for workers.

Traditionally, timber formwork has been used. Timber formwork is built on site by a carpenter who uses timber to create a mould into which concrete can be formed. Typically plywood boards are used to define the sides and bottom of the moulds, and more solid timber frames and bracing used to hold the plywood in place. The use of timber for formwork has certain disadvantages, e.g. timber formwork is only able to be re-used a very limited number of times, it also has the inherent dimensional and structural irregularities associated with a natural product. Moreover, because the formwork is manually installed on-site, tolerances for installation are relatively loose.

Conventional timber formwork for a vertical wall will typically consist of a pair of boards spaced apart by the thickness of the wall to be created. The boards define the opposite surfaces of the wall. The boards are supported and braced on their external sides by timber beams and other bracing to hold them in place. The boards are also tied to each other at intervals to hold the walls of the formwork from moving apart under the pressure of the concrete being poured into the formwork. The ties can be located along the edges of the board or be placed such that they project through the wall of the board to the opposite facing board.

For horizontal structures, such as a floor, the underside of the floor is defined by one or more sheets of timber (e.g. made from plywood) that are supported on timber beams. For elevated floors a temporary support structure needs to be erected before the floor of the formwork can be installed. Such installation is very time consuming and potentially hazardous, particularly when the workers are installing timber panels on the bottom of the formwork section for horizontally extending structures like floors or beams onto the support beams. Around the edges of the timber floor, walls are erected to define a volume into which concrete will be poured. Prior to pouring concrete however, many other elements need to be laid into the formwork so that they can be cast into the concrete. Chief among these are reinforcing bars and conduits for post tensioning tendons, apertures and connections for plumbing and other services.

The placement of each of these additional elements is performed onsite after the formation of the formwork, with each additional job becorning progressively more difficult and hazardous for workers as the working area becomes more cluttered with other elements. For example, in order to install plumbing connections in a floor it may be necessary for the installer to place components between many layers of reinforcing steel or other elements of the building. These elements will also need to be carried or manoeuvred across a surface of the formwork that is criss-crossed by reinforcing bars, associated ligatures holding the steel together and other elements.

After the concrete has cured the temporary formwork then needs to be removed. This is also time consuming and potentially dangerous. In this case workers are removing supports and other structures positioned above their heads. More recently modular temporary formwork systems have been devised. These include panels which have a frame, typically of metal, for providing structural strength. The panel surface defines the inside of the concrete mould. These systems include, corner modules, flat panels etc and the desired formwork shape can be made by joining these together. These systems can be quicker to place than conventional timber formwork because they can be clipped or bolted together and are typically able to be used many times more than conventional timber formwork, but in other respects have similar drawbacks.

One way of partly avoiding work associated with temporary formwork is the use of permanent formwork. For example steel panels can replace the floor of the formwork on horizontal surfaces. These panels are positioned in a very similar manner to that of the timber floor panels of conventional timber formwork but need not be removed afterward as they are formed into the underside of the concrete which they have been used to create. However, in other respects these systems are similar to conventional timber formwork. Forming stairs is especially problematic. Preparing the formwork on site typically requires a skilled carpenter. Pre fabricated formwork modules for forming stairs exist. Whilst some of these modules have been commercially successful, the present inventor considers these modules to be less than ideal. It will be appreciated that the above problems of formwork are generally amplified in the context of stairs due to the relatively complex geometry of stairs compared to that of floors or walls.

One way of ameliorating the complexity, cost and risk of using formwork as described above is to precast the concrete elements off site, but this is only viable in certain situations.

Accordingly, it is an object of the present invention to address one or more of the drawbacks of the prior art systems and/or provide a useful alternative to them. It is not admitted that any of the information in this specification is common general knowledge, or that the person skilled in the art could reasonably be expected to have ascertained, understood, regarded it as relevant or combined it in any way at the priority date.

Summary

Accordingly in its various aspects the invention provides staircases and various components and methods for building staircases. In one aspect the present invention provides a pre-fabricated module for forming a staircase, the staircase including a top end and a bottom end and a plurality of steps with treads and risers therebetween. The module includes: a plurality of transversely extending riser members for forming the risers of a plurality of steps; a floor including a plurality of floor portions, each forming the floor of a respective step; and side portions spanning between a riser member and floor portion along each side of the riser member. The riser members, floor portions and side portions together defining a plurality of voids to receive and form settable material to define the treads of a plurality of steps; wherein the plurality of risers and floor portions are dimensioned such that, when the module is installed at a predetermined angle, the tread of a step formed in a void intersects the riser of an upwardly adjacent step at a distance above the floor to thereby form a slab between the intersection and floor portions.

The module may include one or more elongate structures running along its length capable of being the predominant elongate structural member(s) of the stairs, which structures are preferably integrally formed with the side portions. The riser members, floor portions and side portions may be dimensioned to form a slab of the settable material between the risers and treads and the floor portions when the module is installed at a predetermined angle. Preferably this slab is at least 75mm, and most preferably about 100mm, thick.

The module may include one or more keying structures arranged to project into the settable material from respective locations at or adjacent the floor to key the floor to the settable material to resist shear separation whereby the floor reinforces the settable material by bearing tensile loads. The riser members may constitute the keying structures.

Preferably each riser member includes one or more apertures through which settable material may flow to interconnect longitudinally adjacent portions of the slab.

The module may include structure extending transversely across the floor portions to resist sagging of the floor. Preferably each riser member is connected a respective floor portions at one or more points between the side portions to define said sag resisting transverse structure. Preferably each riser member is connected to its floor portion substantially continuously along its length.

The riser members may each include one or more projecting structures for keying into a longitudinally adjacent portion of settable material. The module preferably includes a respective substantially continuous side wall member on each side; the side wall members defining the side portions. Preferably each side wall member includes a strengthening structure along its upper edge. In preferred forms of the module, each the strengthening structure includes a laterally extending flange which most preferably carries a return flange.

Preferably the module includes two or more like panels, each panel being at least predominantly integrally formed of sheet material and defining one of the floor portions and one of the riser members. Each panel preferably includes an edge portion opposite its riser member; a presentation surface to face outward from the settable material; and a region adjacent its riser member recessed relative to the presentation surface for receiving the opposite edge portion of a like adjacent panel whereby the presentation surfaces of adjacent panels are substantially aligned.

Also described herein is a pre-fabricated formwork module for forming a staircase having risers and treads; the module including:

a floor for at least partly defining a form for receiving and forming settable material; riser members defining the risers; and

structures extending transversely across the floor to resist sagging of the floor.

a floor for at least partly defining a form for receiving and forming settable material; one or more riser members positioned relative to the floor to define a settable material slab between the risers and treads and the floor when the module is installed at a predetermined angle; and

structure arranged to key the floor to the settable material to resist shear separation whereby the floor reinforces the settable material by bearing tensile loads.

In another aspect the invention provides a panel when used in a staircase, the panel being at least predominantly integrally formed of sheet material and including:

a portion defining a portion of floor for forming settable material; and

a portion deflected relative to the floor portion to define a riser member. In another aspect the invention provides a staircase including the above module or panel and a body of material set in the module. The material forming the body is preferably concrete. Preferably the body is unitary in form.

In another aspect the invention provides a method of building a staircase having risers and treads, the method including:

installing a pre-fabricated formwork module so that it is supported substantially only at its ends;

filling the module with settable material;

allowing the settable material to set form a unitary structure including the formwork. In another aspect the invention provides a method of building a staircase having risers and treads, the method including:

installing a pre-fabricated formwork module having a floor and riser members;

filling the module with settable material;

allowing the settable material to set to form a unitary structure including the formwork; and

wherein said filling includes surrounding structure to key the floor to the settable material to resist shear separation whereby the floor reinforces the concrete by bearing tensile loads.

Either method may further include finishing the settable material to form a surface the treads. The finishing may includes using upper extents of riser members as guides.

The various aspects are complementary. Each aspect may incorporate the features described in respect of one or more of the other aspects.

Brief description of the drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an elevation view of a flight of stairs made in accordance with an embodiment of the invention; Figure 2 is a plan view of the staircase of Figure 1 ;

Figure 3 is a transverse cross-section view of the staircase of figures 1 and 2 corresponding to the line A-A in Figure 2;

Figure 4 is a longitudinal cross-section view of a portion of the staircase of Figure 1 corresponding to detail B indicated in Figure 1 ;

Figure 5 is an elevation view illustrating a portion of the staircase of Figure 1;

Figure 6A is an elevation view of a mounting bracket used in the embodiment of Figure 5;

Figure 6B is an end view of the mounting bracket of Figure 6A;

Figure 6C is a plan view of the mounting bracket of Figure 6A; Figure 7 is a perspective view of selected components of the staircase of Figure 1 ;

Figure 8 is an exploded view of the staircase components of Figure 7;

Figure 9 is a cross-section view of a panel of the type illustrated in Figure 8;

Figure 10 is a cross-sectional view of the panel of Figure 9;

Figure 11 is a transverse cross-section view of a stringer used in the embodiment of Figure 7; and

Figure 12 is an elevation of the stringer of Figure 11 ;

Figure 13 is a transverse cross-section view of the staircase in accordance with another embodiment of the invention;

Figure 14 is a longitudinal cross-section view of a portion of the stair case of Figure 13 illustrating two nosing profiles for steps; and Figure 15 is transverse cross-section view of a side of a staircase in accordance with another embodiment of the invention.

Detailed description of the drawings

Described herein is a pre-fabricated module for forming a staircase, the staircase having steps with treads and risers. The module is generally an elongate structure including members for forming risers; and intervening floor portions. There are also side portions on each of its sides. The riser members, floor portions and side portions together define voids to receive a material that sets, preferably concrete, to define the treads of the steps.

Figure 1 illustrates a flight of stairs 1 made using a module according to a first embodiment of the invention. Figure 2 illustrates the staircase 4 in plan view. The flight of stairs 1 is made using a permanent and prefabricated formwork structure according to an aspect of the present invention, in a manner described more fully below. The flight of stairs 1 includes balustrade 2 supported by and carried above staircase 4. As will be described, the staircase 4 is integrally formed with the lower landing 6A and the upper landing 6B. The staircase 4 includes a plurality of steps e.g. 4A. Each step 4A includes a riser 4B, i.e. the generally vertical portion, and a tread 4C, i.e. the generally horizontal portion. In this embodiment, steps have a rise of 190mm, and tread run of about 250mm. As will be described in this embodiment, each step 4A has a contoured riser surface defining an undercut region which extends the effective horizontal tread length of each step 4A. The balustrade 2 includes four balusters e.g. 2A mounted to the staircase 4 at intervals and which support a handrail 2B.

Figure 3 illustrates a cross sectional view through the staircase 4 at line A-A of Figure 2 and shows the construction of the staircase 4 including its permanent formwork components. The permanent formwork components include the floor 8 and a pair of side walls 10. The floor 8 and side walls 10 together define a longitudinal channel (i.e. a channel which extends from the bottom to the top of the stairs) into which concrete 12 is poured to define the steps 4A. Figure 8 illustrates an exploded view of the staircase 4 including a formwork module 3 and concrete structure 12 formed therein. The formwork module 3 includes a pair of longitudinally extending side panels 10 which perform several functions. Firstly they define the side of the formwork for creating the steps 4A of the staircase 4. They also provide longitudinal strength to the formwork structure. In certain embodiments, such as that described below in relation to figures 13 to 15 the longitudinally extending side structures can be designed to support all the live and dead loads of the staircase formed with the module. The side structures also resist outward deformation by the settable material prior to its setting, by forming a channel like structure with the floor, that is supported against outward bowing by the risers 14. The floor 8 is formed of a plurality of panels 14. The panels 14 are arranged so that they form a contiguous floor supported between the side panels 10. A panel 14 is shown in cross section in Figure 9. Each panel 14 extends transversely across the staircase 4 and includes a boundary portion 8A which is more or less planar and in use defines a portion of the floor of the formwork module. An elongate region along a long edge of the panel 14 is deflected relative to the boundary portion 8 A to define a riser member 16. An elongate region 20 running adjacent to the bend 18 is recessed relative to the surface 8B.

Each riser member 16 includes a first generally planar portion 16B extending upwardly from the panel's boundary portion 8A at an oblique angle (in this embodiment the angle is about 105 degrees). The portion 16B extends upwardly to a stepped portion stepping out to a second generally planar portion 16C. The planar portion 16C defines the nose of a step and is arranged to be substantially a vertical when installed. In this embodiment, the second planar portion 16C is about 100mm deep. The portion 16C terminates at its upper extent in a 15mm radius 16D which in use, defines a smooth strong front edge of step 4A.

Each riser member 16 projects away from the floor 8A in a generally upward direction. As will be described, in this embodiment an upper side of each riser member 16 is used to create a formwork section to create a step and abuts the concrete whilst the other is at least partially exposed to define the front face 16A of a riser 16. In this embodiment, the panel 14 is formed from 1.8mm thick galvanised steel (strength grade G450; galvanised finished Z275) sheet. The region 20 is recessed by about 1.8mm relative to a lower, presentation surface 8B of the panel 14. In use, (as shown in Figure 4), the recessed region 20 receives a tail portion 22 (which is on the opposite side of the boundary portion 8A to the recessed region 20) of a like panel 14 such that the presentation surface 8B of adjacent panels substantially align to present an aesthetically desirable outside surface on the non-concrete side of the panel. The overlapping regions 20, 22 are spot welded at regular intervals along their length (i.e. across the width of the staircase 4). Adjacent panels 16 are thereby held in a relative disposition wherein their boundary portions 8A together define a substantially continuous boundary to create the floor 8 of the formwork (i.e. a boundary without significant holes through which significant portions of concrete may escape) for forming concrete.

Referring to Figure 8, the riser members 16 together with the floor 8 and spanning portions of the side walls together define discrete voids 15 each defining mould to form concrete to form a respective step 4A. The concrete 12 steps formed in these voids 15 bear against each other in compression and are restrained from moving in a direction transverse to the stringer 10 by the floor 8. The cells are thought to function like the blocks of antiquated stone stairs which bear against each other and whose relative movement is restrained by a dowel.

Each formwork module 3 including its floor 8, stringers 10 and riser members 16 is configured to suit stairs rising at a specific predetermined angle. When the module is installed at this angle, and the treads 4C are finished e.g. trowelled off. The rear edge of the tread 4C intersects the riser member 16 above it at some distance and defines a slab of concrete, referred to as a throat 24 between the edge and floor. The throat 24 might be thought of as a structural beam upon which the steps are formed.

Of course, the necessary thickness of the throat 24 varies upon a range of factors depending on the specification of the concrete, the specifications of the formwork modules and the length of the flight of stairs. The inventor has found that a throat of at least 75mm thick is a desirable compromise between these and other various competing factors. In this embodiment the throat is about 100mm thick.

As illustrated in Figures 3 and 10 in this embodiment, each riser member 16 includes a series of concrete flow apertures 26 along its lower extent. The concrete flow apertures 26 are arranged in a line and are formed by octagonal punched penetrations having an across face dimension of 70mm and being spaced at a pitch of 120mm. Each octagonal penetration is punched about 7 of its 8 sides leaving one side e.g. the lower horizontal side intact. The octagonal form 28 is deformed about this intact side to a deflected orientation at an angle of 45 degrees relative to the portion 16B of riser member 16. The concrete flow apertures 26 permit concrete to flow between adjacent voids defined by the riser members 16 to interconnect longitudinally adjacent voids that form the steps. As such, the concrete forms a continuous phase of concrete and creates a monolithic structure when set. The deflected portion 28 projects into the concrete of throat 24 serving to key the riser member 16 and the panel in which it is formed into this concrete. This keying action serves to prevent the riser member 16, and in turn the entirety of panel structure 14 moving relative to the set concrete in a direction parallel to the riser portion 16B. This also connects the floor of one panel to the concrete formed in the void above it to resist lateral movement and tension.

Whilst deflecting a portion of material is a convenient means to simultaneously form a concrete flow aperture and a key formation, other forms are possible. By way of example, a strip of angle iron might be fastened to the portion 16B or floor 8B to define a key formation. The apertures can be punched entirely without leaving tabs attached to the riser.

The riser members 16, and in particular the portions between the concrete flow apertures 26, serve to key the panels 14 into the concrete. This is thought to improve the strength of the staircase 4. It will be understood that the floor 8 defines a metal skin along the bottom of the throat 24 and serves to reinforce the throat 24 and in turn the staircase 4. This reinforcing action is thought to be significantly enhanced by the keying effect of lower portions of the riser members 16B embedded in the concrete 12. By keying the floor 8 to the concrete 12 in this way, shear forces between the floor 8 and the throat 24 (e.g. forces resultant from a load applied to the stairs) are resisted whereby the floor 8 of the formwork module 3 bears a significantly greater portion of tensile loads associated with a load applied to the stairs than if the floor 8 were allowed to slide along the throat 24. Accordingly, the described embodiment does not require reinforcing bars.

The stringers 10 are illustrated in more detail in Figures 11 and 12. In this embodiment, each stringer 10 is formed of 3mm thick galvanised steel of the same grade and finish as the panels 14. Each stringer 10 defines an upright wall 10F. The wall 10F runs upwardly along a side of the staircase 4 and forms a sidewall, portions of which form the sides of the voids for forming steps, and the slab (if present). The wall 10F includes at its upward extent, a 20mm wide laterally projecting flange 10A carrying at its outer extent, a 30mm deep downward return flange 10B. The flanges 10A and 10B together constitute a strengthening structure for strengthening the stringer 10 and in turn the staircase 4.

The stringer 10 has an inwardly projecting flange IOC on its bottom edge connected to the wall 10F through a lower portion 10E running along the lower edge of the wall 10F. The lower portion 10E in this embodiment is about 60mm high and separated from upper portions of the stringer 10 by an outward jog 10D so that the lower portion 10E directly underlies the flange 10B. In this way, the stringer 10 and in turn the staircase 4 may be mounted hard up against a planar wall without a gap top or bottom.

As best shown in Figure 3, the respective flanges IOC of the stringers 10 underlie and carry the floor 8 of panels 14. The floor 8 of the panels 14 are welded to each of the horizontal flanges IOC at spaced locations along the length of the staircase 4. In this embodiment, the flange IOC is 60mm wide.

As best illustrated in Figure 8, and as previously mentioned, each panel 14 runs transversely across the staircase 4. The inward surfaces of the stringers 10 abut the ends of the riser members 16 sandwiching the riser members 16 therebetween. The ends of the riser members 16 are fastened to the stringers 10 thus forming a rigid box structure. In this embodiment, the riser members 16 are welded along their end edges to the stringers 10 although other forms of fastening might be employed.

In this embodiment, the panels 14 are formed from rectangular sheet, and as such when fitted between the stringers 10 at each end of the each riser member 16 an aperture 30 (see Figure 3) is defined between the riser member 16 and the portions 10D and 10E of the stringer 10. In use, this aperture 30 is filled with concrete. Alternatively, the riser members might include end portions contoured to mate with the internal surfaces of the stringers 10.

It will be appreciated that the formwork module 3 including the floor 8, stringers 10 and riser members 16 forms a rigid box structure having substantial strength in and of itself prior to the addition of concrete. The two long upper edges of this box structure are reinforced by the flanges 10A and 10B and the two long lower edges are reinforced by the flanges 60 whose effective thickness is increased by the overlying portion of floor 8 welded thereto. Moreover, the riser members being integrally formed with portions of the floor are continuously connected to the floor along their length and as such, serve to significantly strengthen the empty module. In particular, the riser members 16 function as strengthening ribs to prevent the floor 8 'sagging', i.e. bulging downwardly, under the weight of wet concrete. Their connection to the inside walls of the stringers also further minimises outward bowing of stringers.

It will be appreciated that by providing a formwork module strong enough to support wet concrete intermediate temporary propping can be eliminated. The formwork module of this embodiment is desirably installable between formwork defining the landing portions 6A and 6B so as to be supported only by this formwork without intermediate propping. The open concrete receiving area of the formwork module is configured to open into the concrete receiving areas of the formwork modules defining the landings 6A, 6B whereby the staircase 4 and landing 6A and 6B may be integrally formed in a single pour.

It will be appreciated that the described embodiment is relatively simple to install in that it does not require intermediate propping or the addition of reinforcing bars. As such, the preferred embodiment is thought to be not only significantly easier to install, but also significantly cheaper to manufacture because amongst other things, less steel is required than an equivalent permanent formwork and reinforcing assemblies having reinforcing bars. If needed additional reinforcing could be provided and carried in the concrete flow apertures (or purpose-built apertures).

Figure 12 illustrates the end profiles of a preferred form of stringer 10. The end portions of the stringer are shaped to cooperate with the landings 6A and 6B and to present an aesthetically pleasing exterior.

In this embodiment, the panels 14 and stringers 10 are roll formed, although it is contemplated that a range of other manufacturing processes might be employed. By way of example, the stringers might be folded, extruded or moulded. In particular, the language 'deflected portion' as used herein refers to a portion which is angled or offset relative to another portion. The portion might be initially formed in this position, or formed in some other shape (e.g. planar of sheet material) which is deformed to the deflected position. Figure 13 is a cross section, similar to that of Figure 3, but which illustrates a second embodiment of a staircase 4' formed using a second example of a formwork module 3' in accordance with an alternative embodiment of the invention. This embodiment differs from the previous embodiment in that the concrete throat 24 (of figure 4) is, in substance, replaced by strengthened stringers. More specifically, the lower portions of the stringers 10' are shaped such that they cooperate with portions of the floor 8 to define a pair of longitudinally extending support beam members 62.

Each beam member 62 is a hollow tubular section. A horizontal flange 62A projects inwardly from the bottom of the vertical wall portion 10A of the stringer 10' to an upwardly projecting vertical web 62B. A lower portion of the wall 10A, flange 62A and web 62B together define an elongate channel. In this embodiment the channel is about 150mm wide by about 150mm deep. A horizontal flange 62C projects from the top of web 62B towards the centre of the staircase 4'. The floor 8 caps the channel and is welded along its side to the channel and along the flange 62C. The hollow section formed stringers 10' and beams 62 are together capable of being the predominant elongate structural member(s) of the stairs; i.e. in this embodiment bending about a transverse axis associated with live and dead loads applied to the stairs is resisted predominantly by the stringers and beams rather than the formed steps. As such, in this embodiment, the concrete might be replaced by a non-structural settable material. Figure 14 illustrate an alternative two exemplary riser configurations that could be used with this embodiment. Figure 14 is intended merely to illustrate two alternative forms of riser, clearly others are also possible to attain the desired stair profile. Typically all of the risers of a given staircase would be alike.

Figure 14 also shows a shallow throat 24'. Whilst the beams and stringers are capable of bearing the entirety of any applied load, the throat 24' provides some additional support and provides a region for the concrete formed in adjacent voids to bear against each other. This arrangement also creates the appearance of continuous concrete which contributes to the sense of the stairs being sturdy. Figure 15 illustrates an alternative form of beam 62' wherein the web 62B is inclined toward the centre of the staircase 4'. As can be seen the beam 62' in this example is trapezoidal in cross section. Clearly other shapes are also possible.

Figures 5 and 6 illustrate the installation of the balustrade 2 including its balusters 2A and handrail 2B. This mounting involves a mounting bracket 32 as illustrated in Figures 6A, 6B and 6C. The mounting bracket 32 is a rectangular piece 50mm x 150mm x 20mm. The bracket 32 is a thin walled structure open at one of its major faces. The other major face includes a pair of threaded bolting apertures centrally mounted at a pitch of 102mm. As shown in Figures 3 and 5, each mounting bracket 32 is fixed to an exterior of the stringer 10. Each bracket 32 is arranged horizontally with its open face against the stringer 10 and welded in place.

The hand rail 2B is formed by a loop of tubular steel and carried by balusters 2A. Each baluster 2A carries at its bottom end, a mounting bracket in the form of a rectangular webbing having apertures complementary to the apertures of the mounting brackets 32 so that the hand rail to may be bolted thereto. The process for constructing a stair case using a formwork module of the type described herein runs generally as follows:

1. Pre-fabricate the formwork module(s) that are needed for each flight of stairs.

2. Transport the module(s) to the site. For efficiency, delivery will preferably take place in the order of installation. 3. Place the formwork modules on-site to construct the required formwork structure.

4. Connect formwork modules to formwork defining the landings. Connections can be made by welding, bolting or other suitable mechanical fastening, alternatively neighbouring modules can be configured to interlock sufficiently well to not need additional fastening prior to concrete being poured. The landings can be conventional formwork, but preferably are modular permanent formwork. 5. Connect reinforcing, services, ducts or other elements between abutting modules if required.

6. Pour concrete into the assembled formwork. Optionally other materials may also be used to fill the formwork. By way of example filling material may be dispersed through the concrete, or respective larger inserts may be placed into the voids defining the steps and covered with settable material.

7. Finish the concrete as required. This might involve a trowel or a float. A textured finish, e.g. grooves, might be formed in the tread for improved grip. If desired the treads, risers, underside of the floor, and stingers, of the modules can be finished in any suitable manner, e.g. they can be painted, or coated in some other way, or be clad in some other material, e.g. tiles, plaster, render to name some examples.

8. After sufficient curing of the concrete, removing propping from about the landings (if it is used).

As will be appreciated other steps in the construction of a stairs may run in a generally conventional manner.

It will be appreciated that embodiments of the present invention are able to be used with settable materials other than conventional concrete. In the detailed description "concrete" should be interpreted in a broad sense to encompass a wide range of settable building materials.

'Prefabricated' is used herein in its usual sense to refer to a fabricated (or 'manufactured') item transportable to a building side, as opposed to, for example, a wooden form work built in situ.

In particular it should also be noted that some embodiments of the invention provide a formwork module of sufficient structural strength to operate as a staircase without relying on the structural strength of the set material. This is achieved primarily by the strength of the stringers and also the cell like structure of the complete module. Thus the settable material carried by the formwork can include materials not typically considered structural materials e.g. a resin could be set in the formwork to form the surfaces of the stairs. It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

1. A pre-fabricated module for forming a staircase, the staircase including a top end and a bottom end and a plurality of steps with treads and risers therebetween; the module including: a plurality of transversely extending riser members for forming the risers of a plurality of steps; a floor including a plurality of floor portions, each forming the floor of a respective step; and side portions spanning between a riser member and floor portion along each side of the riser member;

the riser members, floor portions and side portions together defining a plurality of voids to receive and form settable material to define the treads of a plurality of steps,; wherein the plurality of risers and floor portions are dimensioned such that, when the module is installed at a predetermined angle, the tread of a step formed in a void intersects the riser of an upwardly adjacent step at a distance above the floor to thereby form a slab between the intersection and floor portions.

2. The module of claim 1 wherein the module further includes openings between pairs of adjacent voids to allow settable material in the module to form a continuous phase of material.

3. The module of either of claims 1 or 2 wherein each opening is formed by an apertures in a riser member through which settable material may flow to interconnect longitudinally adjacent portions of the slab.

4. The module of any one of the preceding claims including one or more elongate support structures running along its length.

5. The module of claim 4 wherein the elongate support structure is capable of supporting live and dead loads to be applied to the stairs after setting of the settable material.

6. The module of either of claims 4 or 5 wherein the elongate support structures are integrally formed with the side portions.

7. The module of any one of the preceding claims wherein the slab is at least 75mm thick.

8. The module of any one of the preceding claims including one or more keying structures arranged to project into the settable material from respective locations at, or adjacent, the floor to key the floor to the settable material to resist shear separation such that the floor reinforces the settable material by bearing tensile loads.

9. The module of claim 8 wherein the riser members define said keying structures.

10. The module of any one of claims 1 to 9 including transverse strengthening structures extending across the floor portions to resist sagging of the floor.

11. The module of claim 10 wherein the riser members are each connected a respective floor portion at one or more points between the side portions to define said transverse strengthening structures.

12. The module of claim 11 wherein each riser member is connected substantially continuously along its length to a floor portion.

13. The module of any one claims 1 to 13 wherein the each riser member includes one or more projecting structures extending outward from a plane of a wall of the riser member for keying into a longitudinally adjacent portion of settable material.

14. The module of any one of claims 1 to 13 including a substantially continuous side wall on each side; the side wall defining the side portions.

15. The module of claim 14 wherein each side wall includes a strengthening structure along its upper edge.

16. The module of any one of claims 1 to 15 including two or more like panels, each panel being at least predominantly integrally formed of sheet material and defining one of the floor portions and one of the riser members.

17. The module of claim 16 wherein said like panels define a floor portion of a lower step and a riser member of an adjacent upper step.

18. The module of either of claims 16 or 17 which further includes a pair of longitudinally extending sections forming at least part of the elongate support structure and the sidewalls of the module; and

a plurality of said like panels supported between the longitudinally extending sections and arranged such that their floor portions at least partly overlap so as to form a continuous floor along the length of the module.

19. A pre-fabricated formwork module for forming a staircase having a plurality of steps having risers and treads; the module including:

a floor for at least partly defining a form for receiving and forming settable material; at least two riser members positioned relative to the floor such that when the module is installed at a predetermined angle, a lower riser member defines a portion of the formwork for forming a step, the tread of which intersects with a riser member above it such that a settable material slab is formed between the intersection and the floor ; and

keying structure arranged to be embedded in the settable material to resist shear separation between the floor and settable material such that the floor reinforces the settable material by bearing tensile loads.

20. The module of claim 19 wherein the slab is at least 75mm thick.

21. The module of either of claims 19 or 20 wherein the keying structure forms part of the riser members.

22. The module of any one of claims 19 to 21 wherein each riser member is connected, substantially continuously along its length, to the floor.

23. The module of any one of claims 19 to 22 wherein each riser member includes one or more apertures through which settable material may flow to interconnect longitudinally adjacent portions of the slab.

24. The module of any one claims 19 to 23 wherein the each riser member includes one or more projecting structures for keying into a longitudinally adjacent portion of settable material.

25. The module of any one of claims 19 to 24 further including a respective wall structure along each side of the floor.

26. The module of any one of claims 19 to 25 including two or more like panels, each panel being at least predominantly integrally formed of sheet material and defining a portion of the floor and one of the riser members.

27. A panel when used in forming a staircase, the panel including:

a floor portion for creating a portion of an underside of a formwork module for forming the settable material to define a first step or portion of a slab supporting a first step; and

a portion deflected relative to the floor portion to define a riser member of a step of the staircase above said first step.

28. The panel of claim 27 wherein the riser member includes one or more apertures through which settable material may flow to interconnect longitudinally adjacent portions of the settable material in the staircase.

29. The panel of either of claims 27 or 28 wherein the riser member includes one or more projecting structures for keying into a longitudinally adjacent portion of settable material.

30. A staircase including:

the module as claimed in any one of claims 1 to 26, or a panel as claimed in any one of claims 27 to 29; and

settable material set so as to form one or more stair treads.

31. The staircase of claim 30 wherein the settable material is concrete.