AU2021221635A1

AU2021221635A1 - Sandwich panel and building module

Info

Publication number: AU2021221635A1
Application number: AU2021221635A
Authority: AU
Inventors: Michael David Stonyer
Original assignee: Reve Architecture Ltd
Current assignee: Reve Architecture Ltd
Priority date: 2021-08-25
Filing date: 2021-08-25
Publication date: 2023-03-16

Abstract

Provided are sandwich panels and building modules which can be joined together to construct a building and associated methods of constructing such panels and modules and of using such sandwich panels and building modules in construction. 6/8 010

Description

6/8

SANDWICH PANEL AND BUILDING MODULE

This invention relates to a sandwich panel and a building module which can be joined

together to construct a building.

BACKGROUND OF THE INVENTION

The construction industry faces a number of unique challenges in providing affordable

housing. The field of building prefabrication attempts to address some of these challenges.

Prefabricated dwellings can be constructed in a factory and then transported to a site. This

offers the advantage that weather and travel of construction professionals are not factors in

the construction process. One downside is that the design of prefabricated dwellings is

limited by the mode of transport and route to the construction site, in New Zealand

predominantly by truck and possibly by rail. This introduces limitations of width and height

of the load to be transported, with the limitation of length being defined by the vehicle.

These limitations are usually addressed in one of two ways: by designing the dwelling to fit

onto a single truck, known as a "tiny house" or by designing the building as modules to be

fitted together on-site.

An advantage of a prefabricated dwelling design is that if the New Zealand Ministry of

Building, Innovation and Employment (MBIE) approves the design, they will grant a multi

proof building consent on the design. This means a building consent application

corresponding to the multi-proof consent documents must be approved by the Building

Consent Authority without questions within 10 days.

Prefabricated dwelling designs made in a factory using conventional components, for

example timber framed construction, are offered as factory-made dwellings and also as kit

sets for constructing on-site. Nookhomes.co.nz offer such transportable homes in both

formats.

Factory-made dwellings using conventional timber-framed construction use a large number

of components and are labour-intensive to assemble, whether on-site or in a factory.

Transporting assembled dwellings introduces a number of additional challenges.

A sandwich panel or structural insulated panel (SIP) is a structure comprising three layers; a

core of low-density insulating material such as polyurethane (PUR) and an outer skin each side of the core. Sandwich panels can thus provide integrated structural and cladding systems. Their strength and light weight means they can span large distances, making them particularly useful for wall and roof systems in commercial or industrial buildings; their use is less common in domestic buildings. Sandwich panels are usually flat and elongate in form, although curved sandwich panels are also available for installation on curved roofs. In use, a side edge of the elongate form is fixed to the side edge of an adjacent panel. For this reason the side edges of the panels are usually designed with complementary profiles to fix together, often employing screw fixings.

As used herein, the term "sandwich panel" means a structure comprising three layers; a

core of low-density insulating material and an outer skin each side of the core.

SUMMARY OF THE INVENTION

In a first broad aspect, the present invention provides a sandwich panel comprising metal

joists within its outer skin.

In an embodiment, the sandwich panel comprises a thermoplastic skin, preferably HDPE,

and an insulating core comprising an insulating material.

The insulating material can be for example a foamed material, preferably a polyurethane

foam or a polyethylene foam, or a mycelium composite material, or another suitable

insulating material, or combinations thereof.

In an embodiment, the insulating material comprises a polyurethane foam, including a

polyurethane foam formed utilising carbon-capture technology, and/or a polyethylene

foam, and/or a foam formed from recycled polyethylene terephthalate (PET).

In an embodiment, the metal joists are steel joists with a tophat profile.

In an embodiment, a surface of the sandwich panel has a ribbed profile to accommodate

the metal joists.

In an embodiment, the metal joists are joined to one another by a cross member fixed

between the metal joists, the cross member preferably being a 100mm steel tophat joist

rivet fixed to the joists at 600mm centres.

In an embodiment, the profile of one side edge is complementary to the profile of the other

side edge, such that two adjacent modules can be joined together without fixings,

preferably wherein one side edge comprises a lip and the other side edge comprises a

complementary crest.

In a second broad aspect, the present invention provides a building module which is a

sandwich panel comprising a first region which provides part of the roof structure of a

building, a second region which provides part of the wall structure of the building, and a

third region which provides part of the floor structure of the building.

In an embodiment, the first and third regions of the sandwich panel are a sandwich panel

according to the first aspect.

In an embodiment, the first and third regions are substantially planar and the second region

is curved in substantially a semicircle, such that the building module is generally U-shaped.

In an embodiment, the building module has a slot extending from the end of the third

region towards the second region to accommodate a metal support, and a hole at the

juncture of the second and third regions to receive a metal support.

In a third broad aspect, the present invention provides a method for constructing a

sandwich panel, comprising:

a. Forming a skin of the sandwich panel from a thermoplastic in a rotary oven and

allowing the thermoplastic to set/cure;

b. Once the skin is set/cured, demoulding the skin and removing at least one end of

the panel;

c. inserting metal joists into the panel;

d. Filling the panel with a foamed material and allowing the foamed material to

harden; or filling the panel with a substrate inoculated with mycelium, and drying

or heating the mycelium after a growth period to form a mycelium composite

material;

e. Once the foamed material is hardened or the mycelium composite material

formed, cutting the excess foamed material or mycelium composite material

flush with the cut panel end(s).

In a fourth broad aspect, the present invention provides a method for constructing a sandwich panel, comprising:

a. Forming a skin of the sandwich panel from a thermoplastic in a mould in a rotary oven and allowing the thermoplastic to set/cure; b. Once the skin is set/cured, demoulding the skin and removing at least one end of the panel; c. inserting metal joists into the panel, and inserting a foam-forming powder into the panel; d. returning the panel and the removed end(s) to the mould; closing the mould and rotating the mould in the oven at a lower heat, to thermally bond the removed end(s) back onto the panel, as well as expand the foam-forming powder to a foam inside the thermoplastic skin.

In an embodiment, in step b) both ends of the panel are removed.

In a fifth broad aspect, the present invention provides a method for constructing a sandwich panel, comprising:

a. Extruding a skin of the sandwich panel from a thermoplastic in an extrusion die; b. Optionally, heating the extrusion and bending the extrusion around a form; c. allowing the thermoplastic to set/cure; d. inserting metal joists into the panel; e. Filling the panel with a foamed material and allowing the foamed material to harden; or filling the panel with a substrate inoculated with mycelium, and drying or heating the mycelium after a growth period to form a mycelium composite material; f. Once the foamed material is hardened or the mycelium composite material formed, cutting the excess foamed material or mycelium composite material flush with the cut panel end (s).

In an embodiment, the method further comprises capping the panel with a thermoplastic end plate using a heat welding process, optionally the thermoplastic end plate is the end plate which was removed in step b).

In an embodiment, the foamed material is a polyurethane foam or a polyethylene foam.

In a sixth broad aspect, the present invention provides a method for constructing a

sandwich panel, comprising:

a. positioning metal joists within a mould for a skin of the sandwich panel, the

metal joists supported and held in place by a number of suitable supports such as

stand-off plugs or other suitable spacer elements;

b. Forming the skin of the sandwich panel in said mould, by adding a thermoplastic

material, and rotating the mould in a rotary oven;

c. (i) allowing the thermoplastic to set/cure, then demoulding the skin with metal

joists within, then forming an aperture in the panel and filling the panel with an

insulating material; or

(ii) allowing the thermoplastic to set/cure, then while the thermoplastic skin is

still warm, forming an aperture in the panel and filling the panel with an

insulating material, then rotating the mould containing the thermoplastic skin

further within the oven at a lower temperature than the melting temperature of

the thermoplastic skin, then demoulding the sandwich panel.

In an embodiment, the insulating material in step c (ii) is a foam-forming powder comprising

polyethylene.

rivet fixed to the joists at 600mm centres.

In an embodiment, the sandwich panel comprises first and third regions which are

substantially planar and a second region curved in substantially a semicircle, such that the

building module is generally U-shaped.

In an embodiment, the U-shaped panel is stood vertically and the foamed material or

substrate is poured in from the top of the U in a controlled manner to fill the entire cavity of

sandwich panel without gaps.

In a seventh broad aspect, the present invention provides a method for constructing a

building from a plurality of modules according to the second aspect, wherein one side edge of said modules comprises a lip and the other side edge of said modules comprises a complementary crest, the method comprising: a. Fixing a first module in place with respect to the ground; b. Aligning a lip of the second module with a complementary crest of the first module, and sliding the second module onto the first module; c. Optionally, fixing the second module in place with respect to the ground; d. Aligning a lip of the third module with a complementary crest of the second module, and sliding the third module onto the second module; e. Repeating steps (c) and (d) until the plurality of modules are installed; f. Fixing the last module in place with respect to the ground.

In an embodiment, every second module is fixed with respect to the ground.

In an embodiment, the building module comprises substantially planar first and third

regions, and the second region is curved in substantially a semicircle, such that the building

module is generally U-shaped, and the building module has a slot extending from the end of

the third region towards the second region to accommodate a metal support, and a hole at

the juncture of the second and third regions to receive a metal support, and the method for

fixing the modules to the ground comprises inserting screw piles into the ground at

positions which will correspond to the end of the slot of each module which is to be fixed to

the ground, to form a first row of screw piles; and inserting screw piles into the ground at

positions which will correspond to the hole of each module which is to be fixed to the

ground, to form a second row of screw piles.

In an embodiment, the method further comprises fixing a bearer beam to each screw pile in

the first row, and fixing another bearer beam to each screw pile in the second row.

In an embodiment, the method further comprises installing a post to each screw pile in the

first row, and fixing a beam to the top of the posts in the first row, prior to step (a).

second row, and fixing a beam to the top of the posts in the first row, after step (f).

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows cross section views of sandwich panels according to two preferred

embodiments of the invention.

FIG. 2A shows a perspective view of a building module according to a preferred

embodiment of the invention.

FIG. 2B shows a perspective view of a building module according to another preferred

embodiment of the invention.

FIG. 3 shows a plan view of a building structural system comprising the building module of

Fig. 2B.

FIG. 4 shows a plan view of a series of building modules according to an embodiment of the

invention.

Fig. 5 shows a front elevation of the building structural system shown in Fig. 3.

FIG. 6 shows a perspective view of a building constructed from the building module of Fig.

2A or 2B.

FIG. 7 shows an exemplary plan view of a building as shown in Fig. 3.

DETAILED DESCRIPTION

Preferred embodiments of the invention will now be described with reference to the

drawings.

Sandwich panel

Fig. 1 shows a cross section view of sandwich panels 100 and 200. Sandwich panels 100,

200 have a width W of 2175 and 2000 mm respectively, although it will be understood by

persons skilled in the art that other widths can be chosen. The depth D of sandwich panels

100, 200 is shown in Fig. 1, and in this example is on the order of 260 mm. While the length

L of sandwich panels 100, 200 is not shown in the cross section drawings of Fig. 1, it will be

understood by persons skilled in the art that sandwich panels usually function as a simply

supported beam and sometimes as a cantilever beam, and that known principles of beam design can be applied to determine the required depth D of the sandwich panel with reference to a given length L, and vice versa.

The sandwich panel has a core 110, 210, and a thermoplastic skin 120, 220. The lightweight

core comprises an insulating core comprising a foamed material which provides rigidity to

the panel. This can be for example a polyurethane foam, including a polyurethane foam

formed utilising carbon-capture technology, or a polyethylene foam, or a foam formed from

recycled polyethylene terephthalate (PET). In other embodiments the lightweight core can

comprise a material such as a mycelium composite. Mycelium composites are formed by

growing mycelium spores on a substrate such as wood chips, agricultural by-products, wool

or fleece.

A preferred material for the thermoplastic skin is polyethylene, for example high-density

polyethylene (HDPE) or linear low-density polyethylene (LLDPE). Thermoplastics have a

number of advantages, including that they can easily be moulded into simple or complex

shapes, and can be heat welded together. The thickness of the thermoplastic skin 120, 220

in this example is about 5 mm. The thermoplastic skin can be formed in a number of ways,

including but not limited rotational moulding, extrusion, and vacuum forming, as is known

to persons skilled in the art. Advantageously, flame-retardant additives can be added to the

thermoplastic skin, as known in the art.

In sandwich panels known in the art, the side edges of the panels are usually designed with

complementary profiles to fix together, often employing screw fixings. The sandwich panel

of the invention comprises a lip 126/226 which fits over a crest 127/227 of an adjacent

sandwich panel.

Sandwich panels 100, 200 comprise steel joists 130, 230. In these examples, steel joists 130,

230 have a profile known as MS Tophat, generally an inverted V-shape with a flat top and

protruding flanges on the bottom which can receive fixings (Fig. 1). In the embodiment

shown in Fig. 1, steel joists 130 have a depth of 150 mm. Suitable steel joists are available

from commercial suppliers including Metalcraft Roofing and Steel and Tube Holdings Ltd.

An advantage of using a commercial steel joist is that span tables are already available.

One side of the thermoplastic skin 120, 220 has a ribbed profile 122, 222 to accommodate

steel joists 130, 230. The other side of the thermoplastic skin has a flat profile 124, 224.

Steel joists in sandwich panels 100, 200 have a spacing J of 290 mm centres and 400 mm

centres respectively, although the person skilled in the art will appreciate that other

spacings are possible. In a preferred embodiment, the steel joists have a cross member

rivet-fixed above the joists at 600mm centres (not shown in Fig. 1). This ensures that the

steel joists sit hard into the troughs in the positions shown in Fig. 1. The cross member can

be for example a 100 mm steel tophat joist.

Ribbed profile 122, 222 can be described as a deep ribbed profile, where the depth of the

ribs is at least half of the depth D of the panel (i.e. D2 ! 0.5 D). In the embodiments shown,

D2 is 103 mm and D is 260 mm.

While inserts 130, 230 are formed from steel, it is contemplated that aluminium joists could

also be used. The high strength-to-weight ratio of steel and aluminium makes these

materials particularly suitable to form the joists. The person skilled in the art will

understand that the joists need not have MS Tophat profiles, but can be any shape which

allows them to function as a beam, including for example open web steel joists and

rectangular hollow sections. Similarly, there is no need to provide a ribbed profile in the

thermoplastic skin in order to accommodate the steel joists. The ribbed profile matching

the profile of the joists 130, 230 provides advantages in forming the sandwich panel or

building module of the invention, as described below.

Once formed, the sandwich panel of the invention is encapsulated by the thermoplastic

skin, which provides weathertightness and durability to the panel. In conjunction with the

foamed material, the metal/steel joists provide the thermoplastic-skin panel with greater

rigidity, enabling the panel to span greater lengths between supports.

Building module

With reference to Fig. 2A, a Building module 10 which is a sandwich panel is shown.

Building module 10 comprises a first region 11 which provides part of the roof structure of a

building, a second region 12 which provides part of the wall structure of the building, and a

third region 13 which provides part of the floor structure of the building.

It is generally expected that the floor region of the building module will be flat for functional

reasons. While the preferred embodiment advantageously has a roof region pitched at 3

degrees to allow for rain runoff and a curved wall region, as discussed further herein, other

arrangements are contemplated.

In this example, regions 11and 13 possess the structure of a sandwich panel 200,

comprising steel joists and an insulating core comprising a foamed material as shown in Fig.

1, ribbed profile for the outer skin, flat profile for the inner skin, and lip 226 (Fig. 2) which

fits over crest 227 of an adjacent building module. Region 12 comprises a thermoplastic

skin having a cross section corresponding with regions 11/13, but filled with foamed

material only. Curved wall region 12 is non-loadbearing and therefore does not have steel

joists.

Fig. 2B shows another building module 20, generally corresponding to building module 10

and comprising first region 11, a second region 12, and third region 13. Building module 20

further comprises slot 21 in region 13, and hole 22 at the junction of regions 12 and 13. The

purpose of slot 21 and hole 22 is described below with reference to a preferred way of

constructing a building. The steel joists inside each module 20 run parallel with, and flank

the slot and hole in each panel. Where interrupted by slot 21, the cross members inside

each module will not cross the entire panel.

In the embodiments shown, building modules 10 and 20 have a width W of 2000 mm,

although it will be appreciated that other widths can be used.

A number of building modules can be fitted together to provide the floor, wall and roof

structure, cladding and insulation of a building of desired length L, being a multiple of the

building module width W. A method for constructing a building from building modules 20 is

described in detail below.

Method for forming sandwich panel and building module

The thermoplastic skin of sandwich panel 100, 200 or building module 10 or 20 can be

formed by rotational moulding. This involves forming a skin of the sandwich panel from a

thermoplastic in a rotary oven. This results in a completely enclosed hollow skin 120, 220.

Rotational moulding ovens are available to fabricate larger items such as storage containers,

water tanks and playground equipment. The building module of the invention can be

formed in a single piece in a large rotary oven. In the preferred embodiment, the length of

building module 10 is on the order of 7 metres, and height on the order of 3 metres. A

suitable oven is available at, for example, New Zealand company Galloway International.

Once the skin is set/cured, it can be demoulded. To insert the steel joists into the sandwich

panel, one end of the panel is sliced off, the joists can then be slid into place. In the case of

a sandwich panel which is a building module 10, the ends of roof region 11 and floor region

13 of the building module are sliced off, the joists can then be slid into place in regions 11

and 13. As mentioned above, in the preferred embodiment, the steel joists are fixed to one

another using a cross member, which can be for example a 100mm steel tophat joist cross

member rivet fixed above the joists at a regular spacing, e.g. at 600mm centres, ensuring

that the steel joists sit hard into the troughs.

Once the steel joists are inserted, the panel is filled with a foamed material, in one preferred

embodiment a polyurethane foam, ensuring that the entire cavity of the sandwich panel is

filled. For the U-shaped building module of the invention, this may be achieved by orienting

the panel with regions 11 and 13 pointing upwards and then pouring or injecting the

foamed material. Once the foamed material has hardened, the excess material is cut flush

with the cut panel end. The end of the panel can then be sealed by heat welding, either

using the previously removed end of the panel, or using a custom-made capping, that is

then heat-sealed using a custom heating plate to melt the cut end and reseal.

In embodiments where a mycelium composite is used, instead of pouring or injecting

foamed material into the panel, a substrate can be inoculated with mycelium spores and

then inserted within the thermoplastic skin. After a growth period, the mycelium can be

dried or heated to form a mycelium composite material.Another way to form the

thermoplastic skin is by extrusion. Either the entire skin 120, 220 can be extruded through a

die to provide the desired profile of the skin, or separate parts of the skin can be formed by

extrusion, for example ribbed side 222 and flat side 224, which can then be welded

together. The joists can then be inserted and the ends sealed as in the rotational moulding

process. To form building module 10 or 20, the extrusion must be bent or wrapped around

a form while in a plastic state.

It will be appreciated by the person skilled in the art that the sandwich panel 100, 200 can

be used to form a roof, floor or wall. While the ribbed profile forms the exterior of building

module 10 or 20, a planar sandwich panel having the cross section shown in Fig. 1 can be

used with the ribbed profile facing either the interior or the exterior of a building.

Alternative method for forming sandwich panel and building module

The rotational moulding process can be used to form the sandwich panel and building

module with the steel joists already positioned within the thermoplastic skin. This can be

achieved by positioning the steel joists within a mould for a skin of the sandwich panel,

supported and held in place by a number of suitable supports, such as stand-off plugs or

other suitable spacer elements. The skin of the sandwich panel can then be formed in said

mould, by adding a thermoplastic material, rotating the mould in a rotary oven and allowing

the thermoplastic to set/cure. Once the skin is set/cured, the thermoplastic skin with steel

joists within can be demoulded. The sandwich panel can then be filled with an insulating

material by forming an aperture in the panel.

In some embodiments, an insulating foam is formed from a powder which is inserted into

the thermoplastic skin while the thermoplastic skin is still warm, i.e. just after it has been

formed in the rotary oven. The powder can be inserted by forming aperture(s) in the

thermoplastic skin, for example by drilling. After the powder is inserted, the aperture

formed by drilling is then plugged. The mould containing the thermoplastic skin is then

rotated further within the oven at a lower temperature than the melting temperature of the

thermoplastic skin. The powder expands to a foam within the mould and adheres to the

thermoplastic skin. Once cooled, the sandwich panel is removed from the mould as a single

integrated piece with no seams. In a particularly preferred embodiment, the thermoplastic

skin is formed from HDPE and the powder is a polyethylene powder.

This method offers the advantage that there is no need to remove the ends of the mould to

insert the steel joists and reseal the ends back onto the mould afterwards. Additionally,

adhesion between the respective polymers is enhanced in embodiments using HDPE skin

and a polyethylene powder. The sandwich panel/building module so formed is seamless

and has a neat finish and simple process of production. Due to the rotational moulding

process, this method would result in some thermoplastic material adhering to the steel joists inside the mould, and it is expected this would result in use of more thermoplastic material per sandwich panel/building module.

Methodfor constructing a building using the building module

The person skilled in the art will appreciate that the building modules of the invention can

be coupled to one another and fixed to the ground in a number of ways to construct a

building. One preferred method is described as follows.

In the preferred embodiment, a screw pile system is used. Screw piles formed from steel

are available from, for example, Katana Foundations (NZ). Screw piles have advantages in

that they are easy to position and quick to install. They also require no concrete placing and

are suitable for deep to soft soil conditions found throughout New Zealand. They can be

removed, allowing for the proposed building to be relocated or recycled at end of life. In

the method of the example, screw piles are installed in the ground in a grid arrangement,

and will each support a steel post P. Screw pile extensions can be coupled to the top of a

screw pile above ground. As used herein, the term "screw pile" refers to a screw pile either

with or without a screw pile extension.

The method of the example uses building modules 20, which slide onto each other as

described further below. Slots 21and holes 22 are useful in the construction method, but

once the building structural system has been erected, all slots 21, and all unused holes 22,

are filled in with moulded inserts of the appropriate shape to fit slot 21 and hole 22.

Figs. 3 and 4 show the grid arrangement of steel posts P at positions P1, P2 etc. Slots 21 and

holes 22 (not shown in Fig. 3; shown in Fig. 4) accommodate the steel posts P. Posts P are

arranged in two parallel rows R and S (Fig. 4). Posts in rows R and S are at a spacing of 2W,

and row R is at a distance X from row S (Fig. 3). In the embodiment shown, X is 4300 mm.

While figs. 3 and 4 show a plan view of a building formed from seven building modules 20, it

will be appreciated that any number of building modules 20 can be used to form a building

in this way.

As shown in Fig. 4, each building module 20 comprises a slot 21 extending from the end of

region 13 to the desired position of row R, and a hole 22 at the desired position of row S.

The distance X2 between hole 22 and the periphery of building module 20 should be

sufficient to locate hole 22 in floor region 13 rather than curved wall region 12. In the

example shown, distance X2 is about 1650 mm and corresponds generally to the radius of

curved wall region 12.

Fig. 5 shows a schematic front elevation of the structural system for a building according to

the invention. In this Figure, a nominal position G is shown for the ground line, and break

lines Rb indicate that the proportion of screw piles R above the ground is indeterminate.

Adjacent screw piles can be coupled above-ground by cross-bracing as required.

Generally, the top of the shaft of each screw pile can be provided welded to a square drive

head. This provides for easy installation of the screw pile and also allows the shaft of the

screw pile to be coupled to a post or a pile extension above, by means of a collar, shown as

Rc in Fig. 5. The collar advantageously comprises a plate or square nut welded to its inner

walls to seat the collar on the square drive head. As is known in the art, the collar can also

comprise holes for fixings such as M12 bolts to pierce the pile shaft and/or post.

To construct the building, two rows R and S of screw piles are installed in any order, at a

spacing related to the width W of the building modules. In the embodiment shown, the

spacing 2W is twice the width W of the building module, and only every second building

module will be fixed to a screw pile (Fig. 5). The spacing can also be e.g. equal to the width

W of the building module, in which case every building module will be fixed to a screw pile,

or another arrangement as will be understood by the person skilled in the art.

The distance between the two rows R, S corresponds to the distance between hole 22 and

the end of slot 21on the building module 20.

Once each row R and S is installed, posts P can be fixed to screw piles in row R, and bearer

beams 23 can be fixed to row R and S respectively, at a height to support floor region 11 of

the building modules. These steps can be done in any order, provided that no posts P are

yet fixed to row S. A bearer beam must be fixed to the screw piles of row S, but it is possible

for a bearer beam 23 to be fixed either to the screw piles of row R (i.e. below collar Rc), or

to posts P in row R (i.e. above collar Rc, shown in Fig. 5).

Bearer beams 23 can be fixed at row R and S respectively using methods known in the art.

The bearer beams can be of any suitable material and profile; a preferred material is hot

dipped galvanized steel, preferably of a parallel flange channel (PFC) profile, which will be

resistant to corrosion and those at row R can for example be fixed to the posts P using a

cleat plate and bolts 25 (shown in Fig. 5).

In this example, each post P is a 89 SHS and is coupled via a collar formed from a 100 SHS to

a screw pile having a circular hollow section (CHS) and a square drive head of comparable

width to post P. However, posts P can be any desired shape, including for example CHS

posts.

Once posts P are installed along row R, a beam 26 is fixed to the top of posts P along row R,

using methods known in the art, to support roof region 11 (Fig. 5). In this example the fixing

means is via cleat plates and bolts 27. A corresponding frame is to be constructed along

row S, but is not yet constructed. Thus, in this example, the entire frame along row R is

installed (both the top beam 26 and a bearer beam 23), and a bearer beam 23 is installed to

row S, before the modules are fixed to the frame.

Next, slot 21of a first building module 20 is slid onto a first post P1 in row R, such that hole

22 aligns with screw pile P2 on in row S (Fig. 3). Slot 21 of the first building module can then

be plugged with a HDPE moulded insert. Post P2 in row S can then be installed through hole

22 to screw pile P2, either at this stage or after all of the building modules 20 are in place.

The moulded inserts can be provided in the appropriate shape to fit slot 21 and hole 22, and

can also be formed by a rotational moulding process. In this example the moulded inserts

are also filled with PUR foam for rigidity. They can be heat welded into place once the

module is installed on the frame.

A lip of a second module is then aligned with a complementary crest of the first module, and

the second building module is then slid onto the first building module. In the embodiment

shown, second building module 20 is not installed to a screw pile; it is held to the first

module by a friction fit. This means that slot 21and hole 22 of the second building module

will not perform a function, and can be plugged with a HDPE moulded insert.

Alternatively, every second building module could be provided without slot 21 and hole 22.

Providing every building module with slot 21 and hole 22 has advantages that only one

mould is needed to form the building modules, and provides flexibility during installation.

It will be appreciated that in alternative embodiments, every building module will have a

complementary pair of screw piles, and every slot 21 and hole 22 will receive a post P.

In this example, the slot 21 is about 1 m in length. Thus, once installed, the floor region of

each module will cantilever 1m beyond gridline R (Fig. 4). Optionally, instead of

cantilevering the floor regions in this way, an additional steel beam could be placed within

each slot 21 to bear on a steel end beam underneath the end of region 13 (not shown).

Advantageously, a balustrade could be fixed to such an additional steel end beam.

As stated above, once each building module is installed on the frame along row R, posts P2,

P4 etc. can then be installed to screw pile P2, P4 etc. via holes 22. When all posts in row S

are in place, a second beam (not shown) can then be fixed to the top of the second row of

posts P2, P4 etc. using methods known in the art, to provide a second frame along row S

and support the roof region 11.

Dimensions of the posts P and beams can be calculated by methods known in the art, with

reference to the required span for beams and the material used, and the load to be borne

by beams/posts. The building modules of the invention are strong and lightweight. For an

unloaded building module 20, a post of 89 mm width is expected to be sufficient. This does

not take account of snow loads; it is also envisaged that the invention will allow for buildings

having green roofs, which increase the load on the structural frame. Calculation of the

required increase to the dimensions of posts P and roof beams in such situations can be

made using known methods. The width of hole 22 and slot 21 are governed by the width of

posts P; for example, hole 22 has a diameter of 120 mm to accommodate a steel post of 89

mm width.

Roof region 11 and floor region 13 can be fixed to the respective beams by fixing screws into

the steel joists within the panels.

While Figs. 3 and 4 and the associated text describe a preferred method for fixing the

building modules to the ground, it will be appreciated that the general approach of providing holes in the floor region of the building module can be adapted to accommodate any foundation system.

Finished building

After forming the shell of a building by the method described above, the open sides of the

building shell may be provided with aluminium joinery, for example double glazed sliding

doors and windows, or with another partition wall system. A perspective view of such a

building is shown in Fig. 6. Joinery can be fixed to the regions 11, 13 using bolting and/or

heat welding techniques. Partition walls can be constructed to the interior of the building

using similar bolting and/or heat welding techniques. An exemplary single-bedroom floor

plan showing partition walls is shown in Fig. 7; it will be appreciated by the person skilled in

the art that many variations are possible.

The surface of the thermoplastic, HDPE in the embodiment shown, is durable and does not

need painting or other finishing, and as discussed above, can accept a green roof system if

desired. The inner surface of the thermoplastic provides a floor surface and exterior deck.

This can provide the finished floor surface, or alternatively a finished floor surface can be

provided on top of the thermoplastic using another floor system.

It is to be understood that, if any prior art publication is referred to herein, such reference

does not constitute an admission that the publication forms a part of the common general

knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description of the invention, except where

the context requires otherwise due to express language or necessary implication, the word

"comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense,

i.e. to specify the presence of the stated feature but not to preclude the presence or

addition of further features in various embodiments of the invention.

Claims

1. A sandwich panel comprising metal joists within its outer skin.

2. The sandwich panel according to claim 1, wherein the sandwich panel comprises a

thermoplastic skin, preferably HDPE, and an insulating core comprising an insulating

material.

3. The sandwich panel according to claim 2, wherein the insulating material is a foamed

material comprising a polyurethane foam; a polyurethane foam formed utilising

carbon-capture technology; a polyethylene foam; and/or a foam formed from

recycled polyethylene terephthalate (PET).

4. The sandwich panel according to claim 2, wherein the insulating material comprises

a mycelium composite material.

5. The sandwich panel according to any one of claims 1 to 4, wherein the metal joists

are steel joists with a tophat profile.

6. The sandwich panel according to any one of claims 1 to 5, wherein a surface of the

sandwich panel has a ribbed profile to accommodate the metal joists.

7. The sandwich panel according to any one of claims 1 to 6, wherein the metal joists

are joined to one another by a cross member fixed between the metal joists, the

cross member preferably being a 100mm steel tophat joist rivet fixed to the joists at

600mm centres.

8. A sandwich panel according to any one of claims 1 to 7, wherein the profile of one

side edge is complementary to the profile of the other side edge, such that two

adjacent sandwich panels can be joined together without fixings, preferably wherein

one side edge comprises a lip and the other side edge comprises a complementary

crest.

9. A building module which is a sandwich panel comprising a first region which provides

part of the roof structure of a building, a second region which provides part of the

wall structure of the building, and a third region which provides part of the floor

structure of the building.

10. A building module according to claim 9, wherein the first and third regions of the

sandwich panel are a sandwich panel according to any one of claims 1-8.

11. A building module according to claim 9 or 10, wherein the first and third regions are

substantially planar and the second region is curved in substantially a semicircle,

such that the building module is generally U-shaped.

12. A building module according to any one of claims 9 to 11, wherein the building

module has a slot extending from the end of the third region towards the second

region to accommodate a metal support, and a hole at the juncture of the second

and third regions to receive a metal support.

13. A method for constructing a sandwich panel, comprising:

allowing the thermoplastic to set/cure;

the panel;

c. inserting metal joists into the panel;

d. Filling the panel with a foamed material and allowing the foamed material to

or heating the mycelium after a growth period to form a mycelium composite

material;

e. Once the foamed material is hardened or the mycelium composite material

formed, cutting the excess foamed material or mycelium composite material

flush with the cut panel end(s).

14. A method for constructing a sandwich panel, comprising:

a. Forming a skin of the sandwich panel from a thermoplastic in a mould in a rotary

oven and allowing the thermoplastic to set/cure;

the panel;

c. inserting metal joists into the panel, and inserting a foam-forming powder into

the panel;

d. returning the panel and the removed end(s) to the mould; closing the mould and

rotating the mould in the oven at a lower heat, to thermally bond the removed

end(s) back onto the panel, as well as expand the foam-forming powder to a

foam inside the thermoplastic skin.

15. The method according to any one of claims 13 to 14, wherein in step b) both ends of

the panel are removed.

16. A method for constructing a sandwich panel, comprising:

a. Extruding a skin of the sandwich panel from a thermoplastic in an extrusion

die;

b. Optionally, heating the extrusion and bending the extrusion around a form;

c. allowing the thermoplastic to set/cure;

d. inserting metal joists into the panel;

e. Filling the panel with a foamed material and allowing the foamed material to

harden; or filling the panel with a substrate inoculated with mycelium, and

drying or heating the mycelium after a growth period to form a mycelium

composite material;

f. Once the foamed material is hardened or the mycelium composite material

formed, cutting the excess foamed material or mycelium composite material

flush with the cut panel end (s).

17. The method according to any one of claims 13-16 respectively, wherein the method

further comprises capping the panel with a thermoplastic end plate using a heat welding process, optionally the thermoplastic end plate is the end plate which was removed in step b) of claim 13 or 14.

18. The method according to any one of claims 13 to 17, wherein the foamed material is

a polyurethane foam or a polyethylene foam.

19. A method for constructing a sandwich panel, comprising:

metal joists supported and held in place by a number of suitable supports

such as stand-off plugs or other suitable spacer elements;

b. Forming the skin of the sandwich panel in said mould, by adding a

thermoplastic material, and rotating the mould in a rotary oven;

c. (i) allowing the thermoplastic to set/cure, then demoulding the skin with

metal joists within, then forming an aperture in the panel and filling the panel

with an insulating material; or

(ii) allowing the thermoplastic to set/cure, then while the thermoplastic skin

is still warm, forming an aperture in the panel and filling the panel with an

insulating material, then rotating the mould containing the thermoplastic skin

further within the oven at a lower temperature than the melting temperature

of the thermoplastic skin, then demoulding the sandwich panel.

20. The method according to claim 19, wherein the insulating material in step c (ii) is a

foam-forming powder comprising polyethylene.

21. The method according to any one of claims 13 to 20, wherein the metal joists are

joined to one another by a cross member fixed between the metal joists, the cross

member preferably being a 100mm steel tophat joist rivet fixed to the joists at

600mm centres.

22. The method according to any one of claims 13 to 21, wherein the sandwich panel

comprises first and third regions which are substantially planar and a second region curved in substantially a semicircle, such that the building module is generally U shaped.

23. The method according to claim 22 when dependent on claim 13 or claim 16, wherein

in step d) of claim 13 or step e) of claim 16 the U-shaped panel is stood vertically and

the foamed material or substrate is poured in from the top of the U in a controlled

manner to fill the entire cavity of sandwich panel without gaps.

24. A method for constructing a building from a plurality of modules according to any

one of claims 9 to 12, wherein one side edge of said modules comprises a lip and the

other side edge of said modules comprises a complementary crest, the method

comprising:

a. Fixing a first module in place with respect to the ground;

b. Aligning a lip of the second module with a complementary crest of the first

module, and sliding the second module onto the first module;

c. Optionally, fixing the second module in place with respect to the ground;

d. Aligning a lip of the third module with a complementary crest of the second

module, and sliding the third module onto the second module;

e. Repeating steps (c) and (d) until the plurality of modules are installed;

f. Fixing the last module in place with respect to the ground.

25. The method according to claim 24, wherein every second module is fixed with

respect to the ground.

26. The method according to claim 24 or 25 wherein the building module is a building

module according to claim 12, and the method for fixing the modules to the ground

comprises inserting screw piles into the ground at positions which will correspond to

the end of the slot of each module which is to be fixed to the ground, to form a first

row of screw piles; and inserting screw piles into the ground at positions which will

correspond to the hole of each module which is to be fixed to the ground, to form a

second row of screw piles.

27. The method according to claim 26, further comprising fixing a bearer beam to each

screw pile in the first row, and fixing another bearer beam to each screw pile in the

second row.

28. The method according to claim 26 or 27, further comprising installing a post to each

screw pile in the first row, and fixing a beam to the top of the posts in the first row,

prior to step (a).

29. The method according to claim 28, further comprising installing a post to each screw

pile in the second row, and fixing a beam to the top of the posts in the first row,

after step (f).

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