AU2019203603B1

AU2019203603B1 - Stair assembly and method

Info

Publication number: AU2019203603B1
Application number: AU2019203603A
Authority: AU
Inventors: Mark Stevens; Summer Stevens
Original assignee: Strictly Stairs Australia Pty Ltd
Current assignee: Strictly Stairs Australia Pty Ltd
Priority date: 2018-06-20
Filing date: 2019-05-22
Publication date: 2020-01-23
Anticipated expiration: 2039-05-22

Abstract

Stair assembly and method Abstract A stair assembly (10) includes a precast landing slab (20), a first flight of precast stairs (40) having an integrally formed bottom landing ((50) and a second flight of precast stairs (80) having an integrally formed top landing (90), wherein an underside of a top step (60) of the first flight of stairs (40) includes a rebate (65) configured to receive a portion of the landing slab (20).

Description

Stair assembly and method

Technical Field [0001] The present disclosure relates to a stair assembly and method. In particular, the present invention relates to a stair assembly and method for residential and commercial construction projects.

Background of the Invention [0002] Installing stairs in multi-story buildings, and in particular high-rise constructions is a complicated construction process which is time consuming and labour intensive. The Australian building standards, and other similar standards around the world specify the required stair dimensions including factors such as allowable tolerances with respect to tread depth and riser height for a given run of stairs.

[0003] In multi-story projects, the stairs, such as internal stairs and fire escape stairs are generally fabricated from concrete. The process of forming up the stairs for concrete pouring in-situ requires significant labour input from form workers, steel workers, concreters and concrete supplies. In addition, it is necessary to manage these distinct trades which can result in lost time on the project.

[0004] Furthermore, when stairs are cast in-situ, the stairs cannot be used by the construction team for several days after the concrete has been poured, which limits access to the upper floors, at the live face of the construction.

[0005] In contrast to in-situ stair fabrication, stairs can alternatively be constructed as a precast element, generally offsite. Normally precast stair runs are cast integrally with the upper and lower landings. This process results in a run of stairs and upper and lower landings which can be installed on site with a crane. Normally the landings are fabricated to be supported on dedicated concrete piers or bearing surfaces which typically project from an adjacent wall.

[0006] However, there are problems which arise with precast stairs. For example, if the height of the floors of the building vary, for example due to the bricklayers being not sufficiently accurate with the amount of mortar applied between each course of bricks or blocks, the construction manager may experience a scenario where the support surfaces do not accurately correspond with the height of the run of stairs.

2019203603 22 May 2019 [0007] Furthermore, the top step in a rise of stairs may be located higher or lower than intended by 20mm or more. As such, the tread of the top step may not be aligned as required with the adjacent landing slab or door openings.

[0008] In this situation, it can be difficult to install the precast stairs. Any attempt to install such dimensionally inaccurate precast stairs is likely to result in dimensional errors at the top or bottom of the rise of stairs, which is likely to make the stairs non-compliant with the building standards. In particular, compliance requirements for fire stairs are very strict in Australia, and many fire stairs installed in high rise buildings are dimensionally deficient. In this scenario, the construction company may face issues with ultimately having the stairs certified as compliant by the relevant certifying authority. The fire codes require a 60/60/60 fire rating to all walls and elements within the stair case area.

[0009] Precast stairs currently in use cannot accommodate variations in the placement of the side and end walls, that is, the horizontal clearance. If the side walls and or end walls move in for instance over 20 mm combined, then the precast will not fit into the gap supplied. It is common practice to have a 20 mm gap between each precast stair and this gap is subsequently filled with a suitable sealant. However, if the side walls and end walls move out over 20 mm, then the gap between the precast and the wall will be too large for mastic fillers.

[0010] Another difficulty with installing precast stairs concerns lowering the stair assembly vertically with a crane into the intended position, without damaging any existing structures such as walls. This can be particularly challenging as the available horizontal clearance between bearing surfaces is often only slightly larger than the dimension of the rise of stairs.

[0011] The crane utilised on a construction site in many circumstances does not have the capacity to lift heavy Building materials like precast concrete elements, in particular precast stairs.

[0012] Metal stair forms are commonly used on construction sites in NSW and also need a crane to lower them into place. These metal stair forms still require mid and upper landings in formwork. They also require steel to be placed into the landings and concreters to place the concrete into the forms and landings and a concrete pump. Regardless of the advantages offered by the metal stairs, there is still a human error factor on account of the finished concrete levels.

2019203603 09 Dec 2019

Object of the Invention [0013] It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages, or at least to provide a useful alternative.

Summary of the Invention [0014] In a first aspect, the present invention provides a stair assembly comprising:

a precast landing slab;

a first flight of precast stairs having an integrally formed bottom landing;

a second flight of precast stairs having an integrally formed top landing;

wherein an underside of a top step of the first flight of stairs includes a rebate configured to receive a portion of the landing slab;

further wherein an upper, lateral edge of the bottom landing includes a bottom landing rebate and an upper lateral edge of the top landing includes a top landing rebate;

the stair assembly further comprising an infill sheet adapted to be received by the bottom landing rebate and an adjacent top landing rebate when the top landing and bottom landing are located side by side.

[0015] In a second aspect, the present invention provides a method of installing a stair assembly including the following steps:

forming or securing a first support member on a wall surface of a stairwell or other structure;

positioning a precast landing slab on the first support member;

forming or securing a second support member on a wall of the stairwell or other structure;

positioning a first flight of precast stairs having an integrally formed first bottom landing and first top landing, a lower end of the first bottom landing being seated on the second support member and the first top landing being seated on the precast landing slab, wherein an upper, lateral edge of the first bottom landing includes a bottom landing rebate;

forming or securing a third support member on a wall of the stairwell or other structure; positioning a second flight of precast stairs having an integrally formed second top landing and second bottom landing, the second top landing being seated on the third support member, and the second bottom landing being seated on the precast landing slab, wherein an upper, lateral edge of the second top landing includes a second top landing rebate, configured to be located adjacent to a third bottom landing rebate of a third flight of precast stairs when the adjacent second top landing of the second flight of precast stairs and a third bottom landing of the third flight of precast stairs are located side by side; and installing an infill sheet which is adapted to be received by the adjacent third bottom landing rebate and second top landing rebate to fill a horizontal clearance located between the

SSTP003AU_second_response_final.docx

2019203603 09 Dec 2019 adjacent third bottom landing and second top landing;

wherein the step of positioning the first flight of precast stairs includes locating a rebate formed in an underside of the first top landing on the precast landing slab.

[0016] There is disclosed herein a stair assembly comprising:

a first flight of precast stairs having an integrally formed bottom landing;

a second flight of precast stairs having an integrally formed top landing;

wherein an upper, lateral edge of the bottom landing includes a bottom landing rebate and an upper lateral edge of the top landing includes a top landing rebate; and an infill sheet adapted to be received by the bottom landing rebate and an adjacent top landing rebate when the top landing and bottom landing are located side by side.

[0017] The stair assembly further preferably comprises a topping slab located on the landing slab, the topping slab having a thickness corresponding to a vertical distance between an upper surface of the top step and an upper surface of the landing slab.

[0018] The precast landing slab preferably includes at least one lifting lug.

[0019] There is disclosed herein a method of installing a stair assembly including the following steps:

positioning a precast landing slab on the first support member;

positioning a first flight of precast stairs having an integrally formed bottom landing with a lower end seated on the second support member and an upper end seated on the first support member;

forming or securing a third support member on a wall of the stairwell or other structure; and positioning a second flight of precast stairs having an integrally formed top landing with a lower end seated on the precast landing slab and an upper end seated on the third support member;

wherein the step of positioning the first flight of precast stairs includes locating a rebate formed in an underside of an upper step on the precast landing slab.

SSTP003AU_second_response_final.docx

2019203603 02 Oct 2019 [0020] The method further preferably includes the step of pouring an infill slab on the precast landing slab to a level generally corresponding with an upper surface of the upper step of the first flight of precast stairs.

[0021] The method further preferably includes the step of placing steel reinforcing and/or steel mesh in the infill slab.

[0022] The first flight of precast stairs and the second flight of precast stairs are each preferably cast in a mould with the mould laying such that risers and treads of the stairs are generally vertical.

[0023] There is disclosed herein a method of installing a stair assembly including the following steps:

positioning a first flight of precast stairs having an integrally formed bottom landing with a lower end seated on the second support member and an upper end seated on the first support member, wherein an upper, lateral edge of the bottom landing includes a bottom landing rebate;

forming or securing a third support member on a wall of the stairwell or other structure; and positioning a second flight of precast stairs having an integrally formed top landing with an upper end seated on the second support member, wherein an upper, lateral edge of the top landing includes a top landing rebate, which is positioned adjacent to the bottom landing rebate; and installing an infill sheet adapted to be received by the bottom landing rebate and the adjacent top landing rebate to fill a horizontal clearance located between the bottom landing and the top landing.

[0024] The first flight of precast stairs and the second flight of precast stairs are cast with voids to reduce the weight of the stair assembly.

Brief Description of the Drawings [0025] A preferred embodiment of the invention will now be described by way of specific example with reference to the accompanying drawings, in which:

6a

2019203603 02 Oct 2019 [0026] Fig. 1 is a schematic perspective view of a three part precast stair assembly according to the present invention;

[0027] Fig. 2 is a top view of a landing slab of the stair assembly of Fig. 1;

[0028] Fig. 3 is a top view of the stair assembly of Fig. 1;

[0029] Fig. 4 is a side view of the stair assembly of Fig. 1;

[0030] Fig. 5 is a partial view of the stair assembly of Fig. 1, showing a detail of the landing slab and a first flight of stairs;

[0031] Fig. 6 is a partial view of the stair assembly of Fig. 1, showing a detail of the landing slab and a second flight of stairs;

[0032] Fig. 7 is a schematic view of a two voided precast flights of stairs having opposing lateral voids on the underside;

[0033] Fig. 8 is a side view of a stair assembly having a culvert stair formation on each of the upper and lower flights of stairs;

[0034] Fig. 9 is a partial detail of the upper flight of stairs of Fig. 8;

[0035] Fig. 10 is a top view of an alternative embodiment of a stair assembly having a perimeter beam; and [0036] Fig. 11 is a cross-sectional view of the stair assembly of Fig. 10.

[0037] Blank paragraph.

2019203603 22 May 2019

Detailed Description of the Preferred Embodiments [0038] A stair assembly 10 and method of fabrication and installation are disclosed herein.

[0039] The stair assembly 10 can be used with different stair configurations, such as stretcher stairs, having an intermediate landing, and scissor stairs, having no intermediate landing, and extending directly between two floors.

[0040] The stair assembly 10 includes a separately formed precast landing slab 20. The landing slab 20 is shown in top view in isolation Fig. 2. The landing slab is fabricated with at least one lifting lug 25 in a region corresponding to the centre of mass, such that the landing slab can be lifted in a generally horizontal configuration from a single lifting point. Referring to Fig. 2, the landing slab 20 is generally in the shape of a rectangle with a corner removed when seen from the top view, and defined by the cut-out 30. The landing slab 20 is precast with internal steel reinforcing bars and/or mesh to meet engineering requirements.

[0041] Referring to Fig 2, the landing slab 20 allows the adjustment of the first precast flight of stairs 40 and the second precast flight of stairs 80 in the direction indicated by the arrows shown on that figure. The width dimension of the landing slab 20 is larger than the width of the two flights of stairs 40, 80. Accordingly, the placement of the flights of stairs 40, 80 permits some adjustment in the direction of the arrows, to ensure the stairs are located at the desired position relative to the vertical walls of the stair well. Once the stairs have been located as desired, it is then possible to measure the spacing between the rebates 140, 150. The technicians can then cut a cement sheet, preferably 20mm thick to place over the clearance 155.

[0042] When the stair assembly 10 is a stretcher stair configuration, the landing slab 20 is normally located centrally to interconnect two separate flights of stairs. In contrast, when the stair assembly 10 is a scissor stair arrangement, which includes a single flight of stairs spanning two floors, the landing slab 20 is located at the top of each flight of stairs.

[0043] In a preferred embodiment, the landing slab 20 is about 150mm thick.

[0044] The stair assembly 10 includes a first precast flight of stairs 40 having an integrally formed bottom intermediate landing 50. The first flight of stairs 40 has a proximal, first step 55 connected to the intermediate landing 50. In the embodiment depicted in the drawings, the first flight of stairs 40 includes eight steps. However, it will be appreciated that the number of stairs may be more or less. The nth, and final step 60, in the depicted embodiment being the eighth step, has a rebate 65 formed on an underside. The rebate 65

2019203603 22 May 2019 extends across the full with of the final step 60. The rebate 65 is defined by two surfaces, that is, a horizontal surface 70, and a vertical surface 75 which are angularly offset relative to each other by about 90 degrees.

[0045] The second means of adjustment is shown in Fig. 1, in the form of a clearance or gap, 67. The gap 67 allows for the movement that may occur with the stair side walls. This can be better shown in Fig 5. In Fig 5 the upper slab extension is longer so as to allow for movement away from the landing slab 20. Depending on the installation, the gap 67 can be as shown in Fig. 5, that is, very narrow. Alternatively, a gap 67 of up to 60 mm between the two precast elements may be present whilst still allowing for adequate bearing contact surfaces.

[0046] The first flight of stairs 40 is cast with internal reinforcing bars and/or mesh. As depicted in Fig. 6, the reinforcing bars may extend horizontally beyond the outer surface of the final step 60.

[0047] Again referring to Fig. 6, where the flight of stairs 80 lands onto the precast landing slab 20, this area can also be packed up so as to accommodate variances in the topping slab 120 levels. The stair assembly 10 allows for movement in every direction, that is, both horizontal plains and vertical directions in every area of contact of all precast elements.

[0048] The stair assembly 10 includes a second precast flight of stairs 80 having an integrally formed top intermediate landing 90. The second flight of stairs 80 has a proximal, first step 85, which is configured to sit on top of the landing slab 20. In the embodiment depicted in the drawings, the second flight of stairs 80 includes eight steps. However, it will be appreciated that the number of stairs may be more or less. The nth, and final step 95, in the depicted embodiment being the eighth step, defines the start of the top intermediate landing 90.

[0049] The operation of the stair assembly 10 and method of installation will now be described. The stair assembly 10 is best suited for fire stairs which are normally installed in a custom fabricated stairwell having masonry or concrete walls.

[0050] Supporting members 100 are secured to the walls of the stairwell such that an upper portion of the supporting member 100 corresponds to the intended underside position of the landing slab 20. In one embodiment, the supporting members 100 are defined by lengths of 150mm x 150mm steel equal angle having a flange width of 12mm. Typically these steel sections will be supplied galvanised or alternatively primed. It will be appreciated

2019203603 22 May 2019 that other steel sections of larger or smaller cross-section may alternatively be utilised, depending on factors such as the weight of the stairs, which will be influenced by the number of stairs, and the width of the stairs.

[0051] In order to meet fire rating requirements, the supporting members 100 may be encased or sprayed with a fire rated material. Also the voided area of the underside or stair throat of the stair may also need to be treated with a fire-retardant.

[0052] The supporting members 100 are mounted to the walls of the stairwell corresponding to the two opposing parallel edges of the landing slab 20, and also the perpendicular, straight edge, without the cut-out 30. In this manner, the supporting members are mounted to three walls of the stairwell. Suitable fasteners are used for mounting the supporting member 100, such as Ramset TM Chemset M16 grade 5.8 Chemset anchor studs, having a length of 190mm. Typically the studs will be placed at 600mm centres or less. However, it will be appreciated that structural engineering details regarding the fastener selection and placement may vary according to the specific installation.

[0053] Once the supporting members 100 are in position, the landing slab 20 is lifted into position by the lug 25 using a crane and the landing slab 20 is seated on the supporting members 100. The landing slab 20 is then securely positioned, and is immediately capable of load bearing.

[0054] Importantly, the landing slab 20 can be moved around on the supporting members 100 so as to accommodate variances in the end walls of the stair well. This enables the installer to solve the problem that if the walls are placed too far apart or too close together adjustments can be made by varying the placement of the precast landing slab 20.

[0055] If the precast landing slab 20 cannot be supported with sufficient wall bearing, for example 150mm, for example because the end walls have been installed too far away from each other, the installer can introduce a supporting member 100 in the form of a steel angle so as to also support the precast landing slab 20.

[0056] Once the landing slab 20 is installed, one or more further supporting members 100 are mounted to the wall of the stairwell to support the bottom intermediate landing 50 of the first flight of stairs 40. The first flight of stairs 40 is then lifted into position, and seated with the rebate 65 being located on top of the landing slab 20. The opposing end of the first flight of stairs 40 at the bottom intermediate landing 50 is seated directly on the support members 100. A clearance of about 10mm is provided between the vertical edge of the landing slab 20 ίο

2019203603 22 May 2019 at the cut-out and the vertical surface of the rebate. This clearance permits thermal expansion and other movement.

[0057] In a similar manner, the second flight of stairs 80 is installed such that the proximal, first step 85, is seated on the landing slab 20, and the opposing end having the top intermediate landing 90 is supported by a further one or more supporting members 100.

[0058] The first and second flights of stairs 40, 80 are installed with the hand rails already fitted. This means that the stair assembly is safe for use as soon as the first and second flights of stairs 40, 80 have been lifted into position.

[0059] In the embodiment described herein, the support member 100 is described with respect to a metal angle secured to the wall. However, it will be appreciated that other support members may be employed, such as dedicated masonry or concrete piers engaged with the walls of the stairwell.

[0060] As such, the installation of the landing slab 20, the first flight of stairs 40 and the second flight of stairs 80 permits quick installation of the stairs which can be used soon after installation. Each of the three precast elements of the stair assembly 10 is capable of load bearing as soon as it is mounted in the stairwell.

[0061] Once the three precast components of the assembly 10 are installed, a concrete infill or topping slab 120 can be poured on top of the landing slab 20, to bring the upper height of the landing slab 20 up to the same height as the final step 60 of the first flight of stairs 40.

[0062] Referring to Fig. 1, a rebate 140 is formed on the upper surface along a lateral edge of the top landing 90, on the inside side, that is furthest from the wall of the stairwell. Similarly, a rebate 150 is formed in the upper surface of the bottom landing 50. In a preferred embodiment, the two rebates 140, 150 are each 20mm wide and 20mm deep. However, it will be appreciated that other dimensions may be used.

[0063] When the first flight of stairs has been installed, and the second flight of stairs 80 has also been installed, the rebates 140, 150 are located side by side and a clearance 155 is defined between the two adjacent landings 50, 90. A sheet of cement sheet, preferably 20mm thick is then placed over the clearance 155. The cement sheeting can be easily and quickly cut to accommodate any size of clearance 155. This provides the flexibility to install the stair flights 40, 80 to suit the site specific dimensions, and the cement sheet which is

2019203603 22 May 2019 subsequently added can be readily customised to the shape of the actual clearance 155 if required.

[0064] In an alternative arrangement where the stair assembly 10 is a scissor stair, the intermediate landing is not present, and the rebates 140, 150 are also included in the landings located at both ends of each flight of stairs 40, 80. At each adjacent set of landings, a cement sheet is deployed to cover the clearance 155 in the manner described above.

[0065] In the scenario that there is no top precast stair landing, the infill of cement sheeting or similar between the two adjacent stair flights can still be deployed.

[0066] Whilst the infill has been described as cement sheeting, it may alternatively be provided by concrete poured in-situ. However the cement sheeting is advantageous as it obviates the need for a concrete pour during stair installation. As such, the only need for concrete placement is when the top landing is poured in with the upper floor slab and live face.

[0067] During this process, any reinforcing steel extending horizontally beyond the edge of the final step 60 becomes embedded in the topping slab 120, which adds strength and structurally ties the topping slab 120 to the first flight of stairs 40. Additional mesh and/or reinforcing may also be added in the topping slab 120 as required.

[0068] The landing slab 20 is provided with a broom finish or similar to enhance bonding between the landing slab 20 and the topping slab 120.

[0069] If the stair well wall height has not been constructed to the intended tolerances, and there are errors in the wall heights, it is possible to make vertical adjustments during the installation. This is achieved by placing packers between the stair risers 40, 80 and the landing slab 20.

[0070] The first flight of stairs 40 and the second flight of stairs 80 may be manufactured in moulds on-site or elsewhere in a dedicated facility. This is achieved by using moulds (not shown) that are laying on their side, such that the stair treads and risers are each extending vertically. The mould includes a support structure to hold the engineered steel reinforcing bars. The mould also permits four or more lifting lugs to be cast directly into the stairs.

[0071] The flights of stairs 40, 80 may include strategically placed voids 110 in the stair side walls and throat either running parallel to the goings and risers and or running the full or partial length of the stair treads and goings. These voids 110 are positioned to reduce the

2019203603 22 May 2019 concrete quantity and overall weight of the stair assembly 10. These voids 110 can be placed within the concrete profile of the stair and can be of any shape or form.

[0072] Similar voids 110 can be placed in the soffit of the stair running the full or partial length of the stair throat. The result can be a culvert or T-beam like outcome or similar, as depicted for example in Figs 7 to 9. The same voided shape can be one long void 110 or the voids 110 can be broken into numerous voids 110 along and around the throat of the stair.

[0073] Referring to Figs. 7 to 9, the culvert arrangement is shown, having a generally central stiffening beam or spine 115, which is steel reinforced and provides adequate strength and rigidity. The two voids 110 are laterally located. This arrangement significantly reduces the amount of concrete required for each of the first and second flights of stairs 40, 80. Accordingly, the stair assembly is significantly lighter. This results is easier lifting and reduced cost. In the culvert arrangement, a horizontal rib 112 is located at the underside of each of the first and second flights of stairs 40, 80 at the top and bottom of the run of stairs. The rib 112 acts as a bearing surface and also provides increased stiffness and strength. The rib 112 intersects the central stiffening beam or spine 115.

[0074] Referring to Figs. 10 and 11, an alternative arrangement is shown, having a reinforced perimeter rib or beam 118 which extends around each of the four sides of the first and second flights of stairs 40, 80. This arrangement also provides adequate strength and rigidity. However, this arrangement permits the void 110 to be centrally located. As such, the beams 118 on the lateral sides provide a greater surface area for hand rail attachment.

[0075] By introducing voids 110, the thickness of concrete will be reduced. This may have an effect on the fire rating properties of the stair assembly 10. In order to comply with fire ratings, the fire rated properties of the precast stair assembly 10 is improved with a fire rated material like Perlite and Vermiculite treated aggregates. This material can be sprayed, rendered, painted or fixed as a sheet application as in Hebal™ or plaster sheeting.

[0076] The voids 110 may be in the form of external voids, as shown in Fig. 7. In the embodiment of Fig. 7, the voids 110 are introduced to the stair throat area, similar to a T-beam.

[0077] Alternatively, the voids may be internal voids 110. Such internal voids are generated by cavities located in the mould used to fabricate the stairs. There are several different concrete casting processes which can be used to generate such an internal or external void 110.

2019203603 22 May 2019 [0078] Referring to Fig. 1, in an alternative embodiment, the top landing slab 20 at the finished floor levels can be replaced by conventional formwork and the precast flights of stairs 40, sits directly on-top of the formwork.

[0079] The mould can stay the same shape and or be altered with an isolated thickening to this area of the precast stair. On the construction site the workers can form up a formwork soffit and add in an edge form for the precast stair to sit on or just sit the precast stair directly onto the soffit and formed-up area.

[0080] This will also alter the way the precast stair going up sits onto the lower landing slab on the lower landing the precast can sit directly onto the landing slab poured below and then place a dowel in straight thru the first going into the landing.

[0081] In the above described alternative embodiment, the mid landing and infill are unchanged.

[0082] During the construction of multi-story buildings, it is common to erect a structural steel frame for the building. The steel frame defines the vertical spaces for the stairwell and elevator shafts. Typically, prefabricated steel stairways with steps and a horizontal pan landing for each floor are installed as the structural steel frame for the building is erected, and each steel stairway and each landing are secured by bolts or by welding to the steel frame members for the building. The landing slab 20 defined herein can replace the steel pan/landing and also act as a brace for the surrounding steel frame structure. Alternatively, the same steel pan/landing can act as a support for the precast flights of stairs 40. The precast flights of stairs 40 can be tied in with location pins or ferrules/bolts and or just sit on the steel landing and later be secured by the placement of the concrete floor slab.

[0083] Typically the floor panels are corrugated steel and they are installed over the steel frame, concrete is then placed onto the steel floor panels to form each concrete floor. If the steel stairway has step pans and a landing pan, concrete is manually poured into the steel pans forming the steps of the stairway and also into the steel pan forming the landing for the stairway halfway between adjacent floors.

[0084] Advantageously, the stair assembly 10 enables access to the working deck or formwork / precast floor areas in a very short amount of time, alleviating the need for ladders and waiting on scaffold access.

2019203603 22 May 2019 [0085] A further advantage of the stair assembly 10 is speed and on-site manpower reduction. In particular, the installation of the stair assembly 10 removes four trades, namely the concrete pump, concreters, form workers and steel fixers.

[0086] Advantageously, the stair assembly 10 accommodates variations in building dimensions in all directions.

[0087] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

The claims defining the invention are as follows:

1. A stair assembly comprising:

a precast landing slab;

a first flight of precast stairs having an integrally formed bottom landing;

a second flight of precast stairs having an integrally formed top landing;

wherein an underside of a top step of the first flight of stairs includes a rebate configured to receive a portion of the landing slab;

further wherein an upper, lateral edge of the bottom landing includes a bottom landing rebate and an upper lateral edge of the top landing includes a top landing rebate;

the stair assembly further comprising an infill sheet adapted to be received by the bottom landing rebate and an adjacent top landing rebate when the top landing and bottom landing are located side by side.
2. The stair assembly of claim 1 further comprising a topping slab located on the landing slab, the topping slab having a thickness corresponding to a vertical distance between an upper surface of the top step and an upper surface of the landing slab.
3. The stair assembly of claim 1 or 2, wherein the precast landing slab includes at least one lifting lug.
4. The stair assembly of any one of claims 1 to 3, wherein the first flight of precast stairs and the second flight of precast stairs are cast with at least one void to reduce the weight of the stair assembly.
5. The stair assembly of claim 4, wherein the voids are defined on either side of a generally central beam located at an underside of each flight of stairs.
6. The stair assembly of claim 5, wherein the void is defined between a plurality of perimeter beams located along underside edges of each flight of stairs.
7. A method of installing a stair assembly including the following steps:

forming or securing a first support member on a wall surface of a stairwell or other structure;

positioning a precast landing slab on the first support member;

forming or securing a second support member on a wall of the stairwell or other structure;

positioning a first flight of precast stairs having an integrally formed first bottom landing

SSTP003AU_second_response_final.docx

2019203603 09 Dec 2019 and first top landing, a lower end of the first bottom landing being seated on the second support member and the first top landing being seated on the precast landing slab, wherein an upper, lateral edge of the first bottom landing includes a bottom landing rebate;

forming or securing a third support member on a wall of the stairwell or other structure; positioning a second flight of precast stairs having an integrally formed second top landing and second bottom landing, the second top landing being seated on the third support member, and the second bottom landing being seated on the precast landing slab, wherein an upper, lateral edge of the second top landing includes a second top landing rebate, configured to be located adjacent to a third bottom landing rebate of a third flight of precast stairs when the adjacent second top landing of the second flight of precast stairs and a third bottom landing of the third flight of precast stairs are located side by side; and installing an infill sheet which is adapted to be received by the adjacent third bottom landing rebate and second top landing rebate to fill a horizontal clearance located between the adjacent third bottom landing and second top landing;

wherein the step of positioning the first flight of precast stairs includes locating a rebate formed in an underside of the first top landing on the precast landing slab.
8. The method of claim 7, further including the step of pouring an infill slab on the precast landing slab to a level generally corresponding with an upper surface of an upper step of the first flight of precast stairs.
9. The method of claim 8, further including the step of placing steel reinforcing and/or steel mesh in the infill slab.
10. The method of any one of claims 7 to 9, wherein each flight of precast stairs is cast in a mould with the mould laying such that risers and treads of the stairs are generally vertical.