Modular building unit

Abstract

A modular building unit (2) comprising a floor assembly (20) at least part of which is formed from a metallic material, or a ceiling assembly (1) at least part of which is formed from a metallic material. The modular building unit (2) further comprises walls (4) coupled to the floor assembly (20) or ceiling assembly (1), the walls (4) including at least one first support element. Each first support element is configured to support a load along a loading axis and each first support element is formed from a non-metallic material along at least a part of the loading axis.

Description

MODULAR BUILDING UNITTECHNICAL FIELD

[0001] The present invention relates to a modular building unit. In particular, the modular building unit is formed from a composite of materials including metallic parts and non-metallic parts (for instance, timber). The present invention further relates to a building constructed at least in part from the modular building unit and methods of constructing buildings.BACKGROUND

[0002] Prefabricated buildings (also known as ‘modular’ buildings) are well known in the construction industry, particularly modular residential buildings such as houses, flats or apartments, and hotels. Modular buildings typically comprise a series of building units which are constructed in a factory, transported to a final location (or site) for the building, and then arranged in a predetermined configuration and coupled together to form the finished building. The modular building units are typically constructed to a substantially assembled form in the factory, in which they can be transported to the final location. Construction of the building can involve stacking one or more upper modular building unit on a lower such unit, so that the upper unit is supported by the lower unit.

[0003] Hybrid buildings have been developed by the applicant which comprise a first building section that is constructed at a final location for the building, and a second building section comprising one or more modular building units constructed in a dedicated facility, away from the final location. A hybrid building of this type can provide advantages including that: construction of the first building section is simplified, with more complex parts of the building provided in the section formed by the modular building unit (or multiple modular building units); and the first building section can provide the primary living space in the building, without being constrained by construction and transport limitations imposed on the modular building unit(s). The hybrid buildings and associated construction techniques are disclosed in International patent publication nos. WO2022 / 243696, WO2022 / 243695, WO2022 / 243694, WO2022 / 243693, and WO2023 / 222853.

[0004] Conventionally, structural elements of a modular building unit are formed from a single type of material. This is partly because it is relatively simple to interconnect portions of a modular building unit when formed from a single material type. Commonly, a structural frame is formed from a metallic material, for instance from steel, which may be welded, bonded, bolted, or otherwise coupled together from a number of separate steel sections. The structural frame may include a floor assembly and / or a ceiling assembly interconnected by a number of walls. In the patent publications identified above, ceiling and floor assemblies can be formed from hot-rolled steel beams and interconnecting walls can be formed from light gauge steel. Light gauge steel beams and struts within the walls transfer load vertically from the ceiling assembly to the floor assembly. The load may be in part the weight of the materials within the modular building unit itself (including the ceiling assembly), and in part the weight of structures overlying the modular building unit in the completed building.

[0005] Metallic materials, particularly steel, have come to represent the default material of choice for forming a structural frame of a modular building unit, partly due to the high strength to weight ratios that can be achieved. The strength of the structural frame is important during manufacture and transport to site as well as within the resulting building. For instance, the structural frame must withstand forces associated with lifting the modular building unit. Forces associated with lifting or transporting a modular building unit can include twisting or shear forces, whereas within the completed building it may be that the majority of the forces are a vertical load applied to the top of the modular building unit and transmitted vertically through the walls which are under compression.

[0006] However, there can be disadvantages associated with this use of a metallic structural frame. Firstly, metals such as steel are relatively expensive materials, which can increase the overall cost of fabricating a modular building unit. Secondly, given that metals transfer heat efficiently, it is necessary to incorporate a large amount of insulation into the fabric of the modular building unit, or to encapsulate the modular building unit within insulation. Thirdly, there is a high environmental cost associated with the use of metals in constructing buildings due to the large amount of embodied carbon owing to the ways in which the metal parts are manufactured. Accordingly, it is known to attempt to form modular building units with non-metallic structural frames, such as using Structurally Insulated Panels (SIPs). A SIP comprises two layers of wood that sandwich a layer of insulation to provide the insulation with support. Typically, the layers of wood may be Orientated Strand Board (OSB). Alternatively, it is known to attempt to form the structural frame of a modular building unit from timber studs. However, owing to actual or perceived concerns about the ability of such timber based modular building units to withstand the forces placed upon them during transportation and in final position within a building, steel framed modular building units remain the most commonly deployed option. As such the benefits associated with using other materials to form a structural frame of a modular building unit have not been fully realised.

[0007] As is discussed within the patent publications identified above, for a hybrid building where a modular building unit is formed from a metallic structural frame, advantageously substantially any construction technique may be used to construct the structural frame of a site-built building section. For similar reasons to those identified above in respect of modular building units, there is a clear motivation to use non-metallic materials where possible. For instance, the walls of a site-built building section that interconnects with a modular building unit may be formed from timber.

[0008] It is known that timber walls are subject to shrinkage. For instance, a timber stud wall that is the height of a typical storey of a residential building (approximately 2.4 m) may shrink vertically by as much as 30 mm in the first year or so after construction as the wood dries out. For a timber stud wall formed from vertically arranged studs and horizontally arranged wooden top and bottom plates, the majority of the vertical shrinkage arises within the top and bottom plates. This is because wood shrinkage occurs primarily perpendicular to the grain: shrinkage along the grain (and hence extending vertically for a vertically arranged timber stud) is negligible. On the other hand, owing to the way that the wood is laid down in OSB, when a SIP is used to form a wall, vertical shrinkage for a SIP wall is less significant.

[0009] It will be readily appreciated that where a timber walled (particularly using timber studs) site-built building section interconnects with a steel framed modular building unit the result is a difference in vertical wall shrinkage rates between the two portions of the building. This difference in vertical wall shrinkage rates is particularly pronounced where the site-built building section is built using timber studs. It is assumed that the steel framed modular building does not shrink vertically at all, or at least negligibly. A difference in shrinkage of 30 mm (or even a fraction of this) can cause major alignment issues between the building sections, such as misaligned flooring at the first floor and higher. Furthermore, the difference in shrinkage may result in cracking of interior finishes spanning the interconnection of the building sections or even structural failure.

[0010] It is an aim of certain examples of the present invention to solve, mitigate or obviate, at least partly, at least one of the problems and / or disadvantages associated with the prior art. Certain examples aim to provide at least one of the advantages described below.BRIEF SUMMARY OF THE INVENTION

[0011] According to a first aspect of the present invention there is provided a modular building unit comprising: a floor assembly at least part of which is formed from a metallic material, or a ceiling assembly at least part of which is formed from a metallic material; and walls coupled to the floor assembly or ceiling assembly, the walls including at least one first support element; wherein each first support element is configured to support a load along a loading axis and each first support element is formed from a non-metallic material along at least a part of the loading axis.

[0012] An advantage of the first aspect of the present invention is that a modular building unit can be constructed from a composite of materials including a metallic material, for instance steel, to form at least parts of a ceiling assembly or a floor assembly (or both) and a timber material to form at least part of the walls. Timber may be in the format of timber studs (that is, posts) or other timber framework. Alternatively, a panellised timber system such as SIPs may be used. This can reduce the overall cost of the modular building unit and the embodied carbon within the modular building unit. At a minimum, at least part of first support elements within the walls are non-metallic along a loading axis (generally vertical) in order to match to shrinkage rates of other parts of a building. More generally, timber is not the only possible non-metallic material for forming the support elements: for instance, a plastics material such as support members formed from polymeric struts can be used. However, of course, timber construction is well established at least for conventional residential buildings, and so may be used conveniently with conventional wall construction techniques. At the same time, the retention of metal structures within the floor or ceiling assemblies can provide torsional stiffness to the modular building unit, thereby reducing the risk of damage (for instance, skewing of the modular building unit) particularly during transportation and lifting.Furthermore, the use of metal structures within the floor or ceiling can provide additional stiffness to a building constructed in part from the modular building unit. Additionally, metal structures within the floor or ceiling can provide a solid connection point within the modular building unit for connection to other structures within a building (including further modular building units and site- built structures).

[0013] Each first support element may be configured to support a load applied to the top of the modular building unit.

[0014] The modular building unit may comprise both a floor assembly and a ceiling assembly, each formed from a metallic material; and the floor assembly and ceiling assembly may be coupled together by the walls.

[0015] The walls may include side structures about at least part of a periphery of the modular building unit. The walls may further include one or more internal walls.

[0016] The ceiling assembly may comprise a load transfer section configured to transfer load to the first support elements, or the floor assembly may comprise a load transfer section configured to receive load from the first support elements. The load transfer section of the floor assembly or the ceiling assembly may be formed substantially entirely from a metallic material. The load transfer section may comprise a metallic frame extending around or proximal to a periphery of the modular building unit; and at least part of the frame may be aligned with a wall. The frame may be formed from connected load transfer section members; and the load transfer section members may comprise box section metallic beams or folded metallic sheet profiles.

[0017] Each first support element may be formed substantially entirely from a non-metallic material. Each first support element may be formed from timber. Each first support element may comprise a timber stud or a timber panel. The timber panel may comprise a structural insulated panel. Each first support element may comprise one or more timber section and one or more metallic section.

[0018] According to a second aspect of the present invention there is provided a hybrid building comprising: a first building section comprising an on-site construction at a final location for the building, the first building section having at least one wall including at least one second support element configured to support a load along a loading axis and formed from a non-metallic material along at least a part of the loading axis; and a second building section defined at least partly by a modular building unit as described above; wherein the first and second building sections are connected together at the final location, the first building section and the modular building unit together forming at least part of a same storey of the building.

[0019] An advantage of the second aspect of the present invention is that building the walls of the first building section and the second building section including support elements that are at least partly non-metallic, the cost and embodied carbon of a building can be reduced. Furthermore, selection of non-metallic materials with similar shrinkage rates to form the support elements in both building sections can prevent or reduce distortion of the building which might otherwise cause damage to interior finishes or structural damage. As an example, walls of both the modular building unit and the first, on-site constructed building section (or at least their respective support elements) may both be formed from SIPs, or both formed from timber studs.

[0020] According to a third aspect of the present invention there is provided a method of constructing a hybrid building, the method comprising: constructing a first building section on-site ata final location for the building, the first building section having at least one wall including at least one second support element configured to support a load along a loading axis and formed from a non-metallic material along at least a part of the loading axis; forming a second building section defined at least partly by a modular building unit as described above; and connecting the first and second building sections together at the final location, the first building section and the modular building unit together forming at least part of a same storey of the building.

[0021] The first and second support elements may be configured to support the weight of the building above the respective walls of the modular building unit and the first building section.

[0022] Shrinkage rates of the first and second support elements along an axis supporting a vertical load may be within 1.25% of one another, optionally 1 %, optionally 0.5%.

[0023] Each second support element may be formed substantially entirely from a non-metallic material. Each second support element may be formed from timber. Each second support element may comprise a timber stud or a timber panel. The timber panel may comprise a structural insulated panel. Each second support element may comprise one or more timber section and one or more metallic section.

[0024] Substantially all load applied vertically to the first and second building sections may be supported by the respective second and first support elements.

[0025] According to a fourth aspect of the present invention there is provided a building comprising: a plurality of modular building units as described above coupled together such that pairs of modular building units interconnect vertically or horizontally.

[0026] The building may comprise a fully modular building or a hybrid building comprising two or more modular building units connected horizontally or stacked vertically.

[0027] According to a fifth aspect of the present invention there is provided a method of constructing a building, the method comprising: coupling together a plurality of modular building units as described above such that pairs of modular building units interconnect vertically or horizontally.

[0028] A further aspect or aspects of the invention may provide a hybrid building construction system, based on or comprising features derived from any one or more of the aspects set out above. The hybrid building construction system may comprise: a first building section configured to be constructed on-site at a final location for a building, the first building section having (or being configured to have) at least one wall including at least one second support element configured to support a load along a loading axis and formed from a non-metallic material along at least a part of the loading axis. The ybrid building construction system may further comprise a second building section defined at least partly by a modular building unit as described above. The first and second building sections may be connectable together at the final location, and the first building section and the modular building unit may together be configured to form at least part of a same storey of the building.

[0029] The modular building unit may be configured to be constructed away from the final location, and may be transportable to the final location in a substantially assembled form.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Examples of the invention are further described hereinafter with reference to the accompanying drawings, in which:Figure 1 is a perspective view of a ceiling assembly forming part of a modular building unit;Figure 2 is a perspective view of a floor assembly forming part of a modular building unit;Figure 3 is an exploded perspective view of part of a modular building unit comprising the ceiling assembly of figure 1 , the floor assembly of figure 2, and three walls formed from SIPs according to an embodiment of the present invention;Figure 4 is an assembled perspective view of the part of a modular building unit of figure 3;Figure 5 is a cross sectional view of part of two stacked modular building units according to figure 4;Figure 6 is a partial view of a hybrid building comprising a first building section including walls constructed from SIPs and a second building section defined at least partly by the modular building unit of figures 3 and 4;Figure 7 is an exploded perspective view of part of an alternative modular building unit comprising the ceiling assembly of figure 1 , the floor assembly of figure 2 and three walls formed from timber studs according to an alternative embodiment of the present invention;Figure 8 is an assembled perspective view of the part of a modular building unit of figure 7;Figure 9 is a cross sectional view of part of two stacked modular building units according to figure 7; andFigure 10 is a partial view of a hybrid building comprising a first building section including walls constructed from SIPs and a second building section defined at least partly by the modular building unit of figures 7 and 8. DETAILED DESCRIPTION

[0031] Turning first to figures 1 to 6, a modular building unit and a hybrid building incorporating the modular building unit in accordance with a first embodiment of the present invention will now be described. The modular building unit of the first embodiment of the invention comprises floor and ceiling assemblies, at least one of which (optionally both) are formed at least in part from a metallic material, for instance steel. As illustrated, the floor and ceiling assemblies are formed from hot or cold rolled steel box sections and folded metallic angle sections. Alternatives will be readily apparent to the skilled person. For instance, substantially the whole of the floor and ceiling assemblies may be formed from hot rolled box section steel. Meanwhile, the walls are formed from timber panels, particularly structural insulated panels (SIPs). According to the present invention at least one of the floor and ceiling assemblies are formed from a metallic material and the walls, or at least support elements within the walls that are configured to support a structural load, are formed from a non-metallic material. This combination of materials allows the beneficial properties of metals such as the ability to resist twisting forces during lifting and transportation to be retained within at least one of the floor and ceiling assemblies, while reducing the amount of metal used inthe construction of the walls. As will be discussed below in connection with figure 7, advantageously the construction of the walls of the module may be selected to match that of an onsite constructed section of a building, such that vertical shrinkage rates are matched.

[0032] Figure 1 illustrates a ceiling assembly 1 of a modular building unit 2 (illustrated in figures 3 and 4). The ceiling assembly 1 comprises a load transfer section 3 extending generally about the periphery and configured to transfer load to walls 4 (illustrated in figures 3 and 4) of the modular building unit 2. Specifically, the load transfer section 3 transfers a compressive load to walls 4 underneath the ceiling assembly 1 , the compressive load comprising the weight of the ceiling assembly 1 itself and the load of any building structures overlying the ceiling assembly 1 (and the modular building unit 2 as a whole). According to an embodiment of the invention, the load transfer section 3 comprises a frame extending around the perimeter of the ceiling assembly 1 and may be formed from a metallic material. The frame is formed from angle section metal, such as steel, and specifically comprises a first part 5 that (as shown in figures 3 and 4) that lies parallel to the walls 4, generally vertically for an assembled modular building unit and a second part 6 comprising a flange that extends from the first part 5. The second part 6 bears upon top surfaces of the walls 4 and transfers load to the walls 4 (including both the load of the ceiling assembly 1 itself and any load applied on top of the ceiling assembly 1). The load transfer section further comprises a third part 7 comprising an inwardly extending flange. It will be appreciated however that the form of the load transfer section 3 may vary, so long as it fulfils the role of transferring load to the walls 4. As such, typically the load transfer section 3 will include at least one part that in use extends generally horizontally and rests on top of a wall. For instance, the load transfer section 3 may comprise a perimeter frame formed from sections of box section metal, such as hot rolled steel, and which in use sits on top of the walls 4 of the modular building unit 2.

[0033] Within the perimeter of the ceiling assembly 1 there is provided one or more structural supports that serve to tie the frame of the load transfer section 3 together and serve to support structures overlying the modular building unit 2 (for instance, a second modular building unit, building services equipment, a roof assembly, or site built sections of a hybrid building). As illustrated, the ceiling assembly 1 comprises a first beam 8 that runs longitudinally (for a rectangular ceiling assembly) and ties together the short sides of the load transfer section 3. The beam 8 may comprise box section steel and may have generally the same height at the first part 5 of the load transfer section 3. There is further shown a plurality of struts 9 (only one of which is identified) that interconnect the load transfer section 3 (resting upon flange 7) and the beam 8. The struts 9 may serve to support building services equipment (for instance, wires, pipes, and ducts) that sits between a plurality of stacked modules. The struts 9 may also support a ceiling material within the modular building unit 2 (that is, underneath the struts 9). An open space 10 is preserved in the embodiment of figure 1 , through which in an assembled modular building unit 2 a staircase may pass (not illustrated). The struts 9 are lower than the top surfaces of the load transfer section 3 and the beam 8 and so preserve a space for services such as wires, ducts, and pipes to be installed without extending above a top plane of the ceiling assembly 1 defined by the load transfer section 3.

[0034] Figure 2 illustrates a floor assembly 20 of a modular building unit 2. Floor assembly 20 is of similar construction to the ceiling assembly of figure 1 . Specifically, the floor assembly comprisesa load transfer section 21 that may be formed from a metallic material, for instance steel. Load transfer section 21 receives load from walls 4 (as illustrated in figures 3 and 4). Load transfer section 21 comprises a first part 22 that extends such that in use it lies vertically alongside walls 4, a second part 23 that comprises an outwards extending flange upon which the walls 4 bear, and a third part 24 comprising an inward extending flange. Flange 24 supports a web of support struts 25 (only one of which is identified) that tie together the load transfer section 21 and serve to support structures within the modular building unit 2, including flooring and internal walls (which may or may not be load bearing). Similarly to the ceiling assembly 1 illustrated in figure 1 , the load transfer section 21 may be provided in alternative forms so long as it functions to received downwards loads from walls. Typically, the load transfer section 21 will include at least one part that in use extends generally horizontally and upon which the bottom edge of a wall will bear. For instance, the load transfer section 21 may comprise a perimeter frame formed from sections of box section metal, such as hot rolled steel, and upon which in use the walls 4 of the modular building unit 2 are seated.

[0035] Figures 3 and 4 show a modular building unit 2 comprising ceiling assembly 1 , floor assembly 20 and walls 4 in exploded and assembled views respectively. Only three walls 4 for a generally cuboid modular building unit 2 are shown, with the fourth wall removed to avoid obscuring internal detail. Walls 2 are formed from timber panels. Particularly, they are form from Structural Insulated Panels (SIPs). SIPs comprise first and second sheets of wood, typically Orientated Strand Board (OSB) that sandwich an insulation layer. The OSB layers provide structural rigidity to the insulation. The walls 4 may be of any dimensions, and may include one or more apertures for doorways and windows. Bottom edges of the walls 4 rest upon the flange 23 of the floor assembly and the flange 6 of the ceiling assembly 1 rests on top edges of the walls 4. It will be appreciated that the walls 4 transfer load from the ceiling assembly 1 to the floor assembly 20 around the periphery of the modular building units defined by the load transfer sections 3, 21 . However, it is not necessary that the walls extend continuously around the modular building unit 2 - there may be gaps, for instance for doorways, or even wholly open sides. It is only required that a sufficient extent of wall extends between the ceiling assembly 1 and the floor assembly 20 to transfer the expected loads.

[0036] The SIP walls 4, particularly the OSB panels, comprises first support elements within the walls 4 of the modular building unit 2. The support elements are formed from a non-metallic material, particularly in this instance wood. The modular building unit 2 comprises a composite modular building unit in that it comprises a combination of materials: ceiling and floor assemblies 1 , 20 at least one of which and optionally both are formed from a metallic material at least in those portions that transfer load to or from the walls 4 (the load transfer sections 3 and 21). It will be appreciated that in some examples one or other of the floor and ceiling assemblies 1 , 20 may have a non-metallic construction, such as being formed from a further SIP. Further, it may be that other than in a load transfer portion formed from a metallic material, a ceiling or floor assembly may be formed from other materials, such as timber. Meanwhile, the walls 4 are formed from a non-metallic material, at least for the support elements that transfer load vertically through the modular building unit 2. For the example of SIPs, the support elements comprise planar components that extend substantially uniformly across the walls other than for apertures provided for windows anddoorways. It falls within the scope of the present invention that a wall of a modular building unit may be constructed from SIP or other timber panels that constitute a relatively small proportion of the wall, with either gaps in between or other materials. All that is required is that those portions of the wall that support a vertically applied load are formed from a non-metallic material such as timber.

[0037] The interconnections between the floor assembly 20, walls 4, and ceiling assembly 1 are shown in greater detail in figure 5 which illustrates a cross section view in a vertical plane through two stacked modular building units within a modular or hybrid house. Particularly, figure 5 shows part of a ground floor module 30 and part of a first floor module 31 stacked on top. Parts of the walls 4 are shown cutaway for clarity, allowing key parts to be presented larger. The internal structure of the SIP walls can be seen: each SIP comprises first and second layers of OSB 32 sandwiching a layer of insulation 33. The top and bottom of each SIP wall is closed off by respective top plates 34 and bottom plates 35.

[0038] For each modular building unit 30, 31 the SIP wall 4 engages the floor assembly 20 such that it bears downwards upon flange 23 and extends parallel to part 22. Inwardly extending flange 24 is also shown. The wall 2 may be secured to the floor assembly 20 by screwing through part 22 into the OSB 32 (and optionally into a top or bottom plate 34, 35). Similarly, it can be seen that the ceiling assembly 1 , particularly flange 6 bears upon the top of each SIP wall 4 and part 5 extends parallel to the SIP wall. Inwardly extending flange 7 is also shown. The wall 2 may be secured to the ceiling assembly 1 by screwing through part 5.

[0039] It can be seen in the cross section view of figure 5 that the flanges 6, 22 do not extend across the full width of the respective top and bottom of the SIP walls 4. This serves to prevent the metallic flanges thermally bridging the SIP wall. The SIP walls 4 of the ground floor and first floor modular building units 30, 31 extend substantially continuously except for where they are separated by the flanges 6, 22 (which may be relatively thin, for instance 5-10 mm each). The outer part of the gap between the stacked SIP walls 4 may be plugged with a thermally resistive yet structurally supportive filler material 36.

[0040] Figure 6 illustrates a hybrid house 40 in partially cutaway perspective view comprising an on-site constructed first building section 41 and a second, modular building section 42 comprising stacked ground floor and first floor modular building units 30, 31 . Accordingly, the second building section 42 is constructed off-site, for instance in a factory or another part of a wider building site, and the modular building units 30, 31 are delivered to the site (the final location of the building 40) and connected to the first building section 31 . The nearest walls of both building sections 41 , 42 and a roof of the building 40 have been removed to reveal internal features.

[0041] The first building section 41 comprises walls 43 that are formed from SIPs. Accordingly, the vertical shrinkage rates of the walls of both building sections 41 , 42 will be the same. The ceilings of each storey of the first building section are formed from posi-joists 44. A posi-joist is a composite ceiling joist system comprising top and bottom timber beams interconnected by a metal web that provides rigidity and also preserves space for installing building services through the posi- joist. Posi-joists will be familiar to the skilled person, though other forms of ceiling structures may be used instead, including other composite ceiling joists such as I-beams (where a planar timberpanel such as OSB replaces the metal web of a posi-joist to interconnect top and bottom timber beams). The posi-joists 44 span between and attach to walls 4 of the modular building units 30, 31 and walls 43 of the first building section 41 to form ground floor and first floor ceiling structures within the first building section 41 .

[0042] The hybrid house 40 of figure 6 substantially entirely comprises walls formed from SIPs. The metallic structure, at least in the load transfer section, of the floor assembly or ceiling assembly (optionally both) in each modular building unit 30, 31 serves to brace the building 40 against twisting. Additionally, metallic floor or ceiling structures advantageously provide a strong attachment point for the posi-joists 44 forming the ceiling structures within the building 40. While it is not necessary that the walls of the modular building units and the walls of the on-site constructed portions of the building have exactly the same construction, it is advantageous that they are the same in order and / or general type to minimise any difference in vertical shrinkage rates between the two building sections. Where they are of different construction (but, for instance, the walls of each building section include timber vertical support elements) it is desirable to constrain the difference in shrinkage rates to less than 1 .25% (for instance, less than 1 .25% difference in shrinkage in the first year post construction) which would provide for a lower degree of differential shrinkage than a module formed with steel reinforced walls and an on-site wall formed from timber studs. That is for respective walls in the first and second building sections that amount of shrinkage along a vertical axis per metre over the first year differs by less than 1 .25%. Preferably, the materials are selected so that the degree of differential shrinkage is less than 1%, optionally less than 0.5%. Where the walls of the two building sections are constructed from closely similar or identical grades of SIPs the difference in vertical shrinkage rates may be negligible.

[0043] Turning now to figures 7 to 10, a modular building unit 70 and a hybrid building 71 incorporating the modular building unit in accordance with a second embodiment of the present invention will now be described. Particularly, figures 7 and 8 show a modular building unit 2 comprising ceiling assembly 1 , floor assembly 20 and walls 4 in exploded and assembled views respectively. The modular building unit 70 of the first embodiment of the invention comprises ceiling and floor assemblies, at least one of which (optionally both) are formed from a metallic material, for instance steel. The ceiling and floor assemblies 1 , 20 may be the same as for the first embodiment of figures 1 to 7 and so the same reference numbers are used, and these will not be described again. Meanwhile, the walls 71 are formed from timber studs 72 (only one of which is identified) in place of SIPs. It can be seen in figures 7 and 8 that the walls 71 are formed from vertically arranged and spaced apart timber studs 72 seated upon a bottom plate 73 and overlaid by two top plates 74 as is conventional in timber stud construction (also referred to as stick or stick-built construction, as well as timber frame construction, depending on factors including an order of construction steps). The bottom plates 73 rest upon flange 23 of the load transfer section 21 of the floor assembly 20. The flange 6 of the load transfer section 3 of the ceiling assembly 1 bears upon the uppermost top plate 74. Collectively, the timber studs 72 and top and bottom plates 73, 74 form the support elements of the walls 71 . As previously described, vertical shrinkage primarily arises in compression of the top and bottom plates 73, 74. Although not illustrated, it will be understood that the gaps between the timber studs 71 may typically be filled with insulation except where openingsare to be preserved. Furthermore, the walls 71 may also be boarded out on the inside or outside (or both).

[0044] Figure 9 is an analogous view to that of figure 5, and shows stacked ground floor and first floor modular building units 90, 91 constructed according to figures 7 and 8. The structure of the timber stud walls 71 can be seen in cross section coupled to the ceiling and floor assemblies 1 , 20. As for figure 5, a thermally resistive and structurally supportive filler piece 36 fills the width of the walls 71 beyond the flanges 6, 22 of the ceiling and floor assemblies to prevent thermal bridging. The interaction between the ceiling and floor assemblies is generally the same as already described in connection with figure 5, and so will not be described again.

[0045] Figure 10 is an analogous view to that of figure 5, and shows a hybrid building 100 comprising a first, on-site constructed building section 101 and a second, modular building section 102 comprising stacked ground floor and first floor modular building units 90, 91 constructed according to figures 7 and 8. The walls 103 of the first building section 101 are of a timber stud construction matching the timber stud construction of walls 71 of the modular building units 90, 91 , thereby ensuring closely matched vertical shrinkage rates. As for figure 5, the ceilings of the first building section 101 may be formed from posi-joists 44.

[0046] As previously noted, wood shrinkage occurs primarily perpendicular to the grain: shrinkage along the grain (and hence extending vertically for a vertically arranged timber stud) is negligible. Accordingly, for a further embodiment of the invention (not specifically illustrated) the timber top or bottom plates 73, 74 shown in figures 7 and 8 may be used in combination with light gauge steel studs (or other metallic studs) in place of timber studs 72 to form the first support elements of the module walls. By providing at least some timber (more generally, a non-metallic material) within the vertical loading axis of walls 71 , it may be configured that the vertical shrinkage rate of the walls of the modular building unit 70 may be closely matched to a vertical shrinkage rate of an accompanying site-built building section (for instance using wholly timber stud wall construction as illustrated in figure 10). A further option would be for the walls of the site-built section to also include second support elements comprising one or more timber plate and light gauge steel studs. At its most general, the present invention requires only that first support elements within the modular building unit define a (vertical) loading axis and are formed from a non- metallic material along at least part of that loading axis. For the example of timber stud construction (or light gauge steel studs in combination with one or more timber plate) the support element comprises the combination of studs and plates: everything contained between the floor and ceiling assemblies of the modular building unit that transfers load.

[0047] For the embodiment of figures 1 to 6 and the embodiment of figures 7 to 10 the first support elements within the walls of the modular building unit (the SIP panels and the timber stud walls respectively) may support a load arising within the modular building unit itself. For instance, they may support the weight of the ceiling assembly. They may additionally support a load applied to the top of the modular building (either applied directly to the walls or via the ceiling assembly if one is present). Either type of load, or both in combination, may be termed a structural load. A load applied to the top of a first modular building unit may comprise a load formed by a further modular building unit stacked on top of the first modular building unit. Or it may comprise a load formed byanother section of a building, such an on-site constructed building section that is (partly) supported by the modular building unit. In some cases, a load formed by an on-site constructed building section that extends over a modular building unit may not be applied to the modular building unit: it may be supported by a structure that spans over the top without transferring load.

[0048] It will be understood that the first support elements are intended to bear the whole or substantially the whole of the load applied to a wall of a modular building unit. For instance, a first support element may comprise a vertically orientated timber stud within a timber stud wall. Alternatively, a first support element may comprise a SIP. It will be understood that particularly for a timber stud wall there may be additional structural elements of the wall, such as insulation between studs, noggins, and cross bracing (for instance, OSB spanning two or more studs and fixed to the studs). However, typically the wall construction is such that the additional elements do not materially contribute to the transmission of structural load vertically through the walls: this being restricted to the vertically arranged timber studs and the top and bottom plates.

[0049] Furthermore, where a wall is constructed with first support elements that are formed from wood (or more generally, a non-metallic material), this does not exclude the possibility that the wall may include at least some metallic material, including for cross bracing. However, for the purposes of the present invention it is considered that any metallic elements present within a timber wall will negligibly contribute to the transmission of structural load vertically through the walls.

[0050] In some examples, a modular building unit may include one or more walls formed from SIPs and one or more walls formed from timber studs. For instance, the walls of the modular building unit that form part of the exterior of the hybrid building may be formed from SIPs that interconnect with exterior SIP walls of the first building section. Walls of the modular building unit that face into the interior of the first building section may be formed from timber studs. In this situation the SIPs within the modular building unit define the first support elements. The timber stud walls of the modular building unit may not significantly support a structural load. Alternatively, the modular building unit SIP walls may comprise primary support elements for which the shrinkage rate is closely matched to that of the SIP walls of the first building section, and the studs of the stud wall may comprise secondary support elements.

[0051] It will be understood that where the purpose of including non-metallic materials within the support elements of a modular building element is to match vertical shrinkage rates of an adjoining site-built building section then this will require a detailed understanding of both the loads applied to walls in different portions of a building and the properties of the selected materials. For instance, it may be that the load applied to the top of a modular building unit in a hybrid building may differ from the load applied to the top of a wall within a site-built section of the hybrid building. Similarly, for the example of timber being used as part or the whole of a support element within a modular building unit, it may be necessary to calculate the type of timber and how it has been processed or treated, orientation of the grain, and dimension of any timber element to determine how it will shrink over time.

[0052] The embodiments of the present invention described relate to the use of composite modular building units in hybrid buildings (as illustrated in figures 6 and 10 particularly). In such a hybrid building a first, on-site constructed building section and a second off-site constructed buildingsection comprising at least one composite modular building unit are arranged so that they collectively define at least one storey of the hybrid building. As illustrated, further composite modular building units may be included, for instance a stack of two or more such modular building units. However, the use of composite modular building units according to the present invention is not restricted to hybrid buildings: a fully modular building may be provided by forming, off-site, a plurality of composite modular building units in which at least part of at least one of a ceiling and a floor assembly is formed from a metallic material and at least vertical support elements forming walls of the units are formed from a non-metallic material. The plurality of composite modular building units may be arranged side-by-side, stacked, or some combination of both.

[0053] Throughout this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other components, integers, or steps. Throughout this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Throughout this specification, the term “about” is used to provide flexibility to a range endpoint by providing that a given value may be “a little above” or “a little below” the endpoint. The degree of flexibility of this term can be dictated by the particular variable and can be determined based on experience and the associated description herein.

[0054] Features, integers, or characteristics described in conjunction with a particular aspect or example of the invention are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification, and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing examples. The invention extends to any novel feature or combination of features disclosed in this specification. It will be also be appreciated that, throughout this specification, language in the general form of “X for Y” (where Y is some action, activity or step and X is some means for carrying out that action, activity or step) encompasses means X adapted or arranged specifically, but not exclusively, to do Y.

[0055] Each feature disclosed in this specification may be replaced by alternative features serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0056] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS:1 . A modular building unit comprising: a floor assembly at least part of which is formed from a metallic material, or a ceiling assembly at least part of which is formed from a metallic material; and walls coupled to the floor assembly or ceiling assembly, the walls including at least one first support element; wherein each first support element is configured to support a load along a loading axis and each first support element is formed from a non-metallic material along at least a part of the loading axis.

2. A modular building unit according to claim 1 , wherein each first support element is configured to support a load applied to the top of the modular building unit.

3. A modular building unit according to claim 1 or claim 2, wherein the modular building unit comprises both a floor assembly and a ceiling assembly, each formed from a metallic material; and wherein the floor assembly and ceiling assembly are coupled together by the walls.

4. A modular building unit according to any one of the preceding claims, wherein the walls include side structures about at least part of a periphery of the modular building unit.

5. A modular building unit according to claim 4, wherein the walls further include one or more internal walls.

6. A modular building unit according to any one of the preceding claims, wherein the ceiling assembly comprises a load transfer section configured to transfer load to first support elements, or the floor assembly comprises a load transfer section configured to receive load from first support elements; and wherein the load transfer section of the floor assembly or the ceiling assembly is formed substantially entirely from a metallic material.

7. A modular building unit according to claim 6, wherein the load transfer section comprises a metallic frame extending around or proximal to a periphery of the modular building unit; and wherein at least part of the frame is aligned with a wall.

8. A modular building unit according to claim 7, wherein the frame is formed from connected load transfer section members; and wherein the load transfer section members comprise box section metallic beams or folded metallic sheet profiles.

9. A modular building unit according to any one of the preceding claims, wherein each first support element is formed substantially entirely from a non-metallic material.

10. A modular building unit according to any one of the preceding claims, wherein each first support element is formed from timber.

11. A modular building unit according to claim 10, wherein each first support element comprises a timber stud or a timber panel.

12. A modular building unit according to claim 11 , wherein the timber panel comprises a structural insulated panel.

13. A modular building unit according to any one of claims 1 to 8, wherein each first support element comprises one or more timber section and one or more metallic section.

14. A hybrid building comprising: a first building section comprising an on-site construction at a final location for the building, the first building section having at least one wall including at least one second support element configured to support a load along a loading axis and formed from a non-metallic material along at least a part of the loading axis; and a second building section defined at least partly by a modular building unit according to any one of the preceding claims; wherein the first and second building sections are connected together at the final location, the first building section and the modular building unit together forming at least part of a same storey of the building.

15. A method of constructing a hybrid building, the method comprising: constructing a first building section on-site at a final location for the building, the first building section having at least one wall including at least one second support element configured to support a load along a loading axis and formed from a non-metallic material along at least a part of the loading axis; forming a second building section defined at least partly by a modular building unit according to any one of claims 1 to 13; and connecting the first and second building sections together at the final location, the first building section and the modular building unit together forming at least part of a same storey of the building.

16. A hybrid building according to claim 14 or a method according to claim 15, wherein the first and second support elements are configured to support the weight of the building above the respective walls of the modular building unit and the first building section.

17. A hybrid building or a method according to any one of claims 14 to 16, wherein shrinkage rates of the first and second support elements along an axis supporting a vertical load are within 1.25% of one another.

18. A hybrid building or a method according to claim 17, wherein shrinkage rates of the first and second support elements along the axis supporting a vertical load are within 1 % of one another.

19. A hybrid building or a method according to claim 18, wherein shrinkage rates of the first and second support elements along the axis supporting a vertical load are within 0.5% of one another.

20. A hybrid building or a method according to any one of claims 14 to 19, wherein each second support element is formed substantially entirely from a non-metallic material.21 . A hybrid building or a method according to any one of claims 14 to 20, wherein each second support element is formed from timber.

22. A hybrid building or a method according to claim 21 , wherein each second support element comprises a timber stud or a timber panel.

23. A hybrid building or a method according to claim 22, wherein the timber panel comprises a structural insulated panel.

24. A hybrid building or a method according to any one of claims 14 to 19, wherein each second support element comprises one or more timber section and one or more metallic section.

25. A hybrid building or a method according to any one of claims 14 to 24, where substantially all load applied vertically to the first and second building sections is supported by the respective second and first support elements.

26. A building comprising: a plurality of modular building units according to any one of claims 1 to 13 coupled together such that pairs of modular building units interconnect vertically or horizontally.

27. A method of constructing a building, the method comprising: coupling together a plurality of modular building units according to any one of claims 1 to 13 such that pairs of modular building units interconnect vertically or horizontally.

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