Installation system for a doorset and a method of use thereof

Abstract

An installation system for installing a doorset in a wall, the wall comprising a doorset and a sub-frame 20 wherein the doorset comprises a door and a frame having a sidewall around its perimeter for

Description

The present invention relates to an installation system for a doorset that facilitates the installation of a doorset across an opening in a wall. The system is designed to 5 accommodate plasterboard of a wall liner. The doorset comprises at least one door and a frame around at least part of a perimeter of the door. It is a common building practice to line a wall with a wall liner system, a practice also known as dry lining or dry walling, and to incorporate a door or doorset into that lined 10 wall across an opening in the wall and wall liner. A purpose of using a wall liner system is to install a new plasterboard face on an underlying wall, which can offer certain benefits. For example, wall liner systems are particularly effective at correcting surface irregularities on the underlying wall, and some 15 wall liner systems can be installed with little or no background preparation of the underlying wall. Some wall liner systems can be installed directly onto the underlying wall (even one with significant surface irregularities) without any need to clean the wall back to a smoother 20 finish, save in extreme circumstances. Typically, existing wall liner systems create a cavity behind the new plasterboard face -between the back of the plasterboard and the underlying wall. This cavity provides a further potential benefit in that it can be infilled with insulation, commonly of either (or 25 both) a thermal or sound insulation type. The cavity can also or instead be used to accommodate service runs, such as for electric wires or as cabling or pipework conduits, such as for audio or video cabling, internet cabling or water or gas pipework. Numerous wall liner systems exist for dry lining a wall. For example, there is GypLyner® 30 by British Gypsum®, the Tradeline® Wall and Ceiling Lining System, and the Knauf® Wall Liner System. These and most other wall liner systems involve attaching a framework to the wall, generally using adjustable U brackets on the wall (commonly a folded metal strip with multiple screw holes) to space from the underlying wall a series of subsequently fitted vertical or horizontal studs (usually connected to the U brackets 35 using self-tapping screws). The studs will typically extend parallel to one another to 30 10 23 provide the framework that is spaced from the wall by the U brackets, that spacing defining the cavities mentioned above. In recent years, some commercial offerings for wall liner systems come with fire or load 5 rating certifications, or meet particular regulatory Standards when installed in their intended configuration. These certifications and Standards are important in some countries, such as the United Kingdom, as a new buildings, and certain renovation projects - particularly commercial renovations - will need to meet certain regulatory Standards in order to pass building control inspections and the like. 10 A conventional door can be fitted into a wall fitted with a wall liner system by fitting plasterboard around an opening in the underlying wall and the liner system and screwing a frame for the door to the underlying wall with long screws - either through the plasterboard that lines the opening, or directly to that underlying wall if the plasterboard 15 is fitted after the frame. The door can then be installed within the frame. A difficulty with such adaptations of wall liner systems is that this, however, is that most commercial wall liner systems are not designed or tested to accommodate a door or window. As a result they offer no support or fixings to elements of the frame or the door. Neither do they possess integrated load bearing ability for any element of the door, such as the hinge 20 points. Furthermore, fire integrity of wall liner system is lost when a hole is cut through it to accommodate a door or window. The present invention seeks to provide a Standardised installation system to overcome this. The present inventors have realised that some doors are provided as a doorset - with a 25 frame, and as such the frame may be of a pre-set size. Such doorsets are starting to be provided with fire or load rating certifications, or to meet particular regulatory Standards when installed in their intended configuration. However, they also realise that the presence of the frame can complicate the installation - particularly for doors intended to be flush fitted to the level of the new plasterboard face for the room. This is because 30 these doorsets are commonly deliberately designed to be low profile so as to enable a flush fit with the finished surface of the wall, whereby they are commonly not deep enough to engage fully with the underlying wall - often only extending rearwardly by 30-50mm, and thus overlying only the cavity and the plasterboard. As such they cannot be so fitted; the wall screws, if fitted through the frame of the doorset, would not be able to 35 reach the underlying wall! Instead they would only extend into the cavity behind the 30 10 23 plasterboard face (or if they were to engage the underlying wall, they would not do so securely, as they would be too close to the surface of the underlying wall, rather than being generally central to the underlying wall, thus risking cracking the wall during fixation. 5 To remedy this, in the prior art the installers of such wall liner systems have attempted to positioned the closest stud of the wall liner system close to the opening to try to allow engagement of the wall screws with that stud. However, this complicates the installation of the framework of the wall liner system, and likely only helps down one side of the door, 10 unless the stud on the other side is also specifically positioned. That latter approach, however, can cause uneven distribution of the studs on the wall - an undesirable approach as subsequent wall fittings commonly are sized to fit with a given stud spacing. Such uneven distribution can also occur if the door’s desired position is not conveniently placed adjacent one of the studs, as can often occur with retrofitted doors, thus requiring 15 additional studs to be inserted, or existing studs to be moved. Furthermore, such prior art installations tend to leave gaps between the door frame and the underlying wall, especially where there is a wide cavity for service runs or insulation, or simply where the underlying wall is particularly non level, or where a non-straight wall 20 - for example along a corridor - is being attempted to be straightened by use of the wall liner system. The gap in these installations create problems as they can compromise the integrity of the wall, particularly in the case of a fire door. Indeed, such prior art installations generally 25 will not meet building regulations or equivalent fire or smoke safety standards for a fire door, even if the door or the doorset and the underlying wall are both themselves compliant with the relevant fire safety standards or regulations. This can occur as the door or doorset is tested for a specific form of installation, and installing with a drywall system is different to such standard test installations. This lack of compliance, whether 30 real or theoretical, can lead to a lack of official sign-off on a build project. It can also lead to a higher risk or likelihood of fire or smoke transmission through the building in the event of a fire, and potentially, or more recently a likely, invalidation of the property’s insurance, as building control and fire integrity or safety inspectors are now inspecting the integrity of door installations more carefully. 30 10 23 The present invention seeks to provide an alternative mode of installation for a door or a doorset in an opening in a wall featuring a wall liner system, whereby wall integrity can be maintained for ensuring compliance with relevant building regulations or equivalent fire or smoke safety standards for an installation of a fire door / doorset in a wall, such as, 5 in the UK, the Building Safety Act or the Defective Premises Act or the proposed Construction Products Regulation (or CPR) that is intended to include regulatory requirements for meeting so as to provide “safety in use” and “safety in foreseeable misuse” circumstances, the latter of which such a doorset installation in a wall liner system might be. 10 According to the present invention there is provided an installation system for installing a doorset in a wall, the wall featuring: a) a wall liner system comprising at least one plasterboard sheet; 15 b) an underlying wall; c) a wall opening for the installation system through both the underlying wall and the at least one plasterboard sheet; and d) a cavity between the plasterboard sheet of the wall liner system and the underlying wall; 20 and the installation system comprising a doorset and a sub-frame, wherein: the doorset comprises: i) a frame comprising a sidewall around its perimeter for extending into the wall opening and a laterally extending flange extending from the sidewall for engaging over the plasterboard around the wall opening; and 25 ii) at least one door within the frame; and the sub-frame comprises at least one sub-frame component in the form of a metal sheet having a length of at least 500mm, and having a substantially constant cross section, the cross section defining a leg part and a foot part when viewed in section, the foot part comprising a kink in its section to provide a step that defines a space into which 30 the plasterboard will be fitted, and the leg part being for bridging the cavity between the underlying wall and the plasterboard, the sub-frame extending around substantially all of the sidewall of the frame, and being for providing an inner opening inside the wall opening for receiving the doorset, wherein, upon installation of the doorset, the sidewall of the doorset extends into both the wall opening and the inner opening, and the laterally 30 10 23 extending flange of the frame extends from the sidewall in front of the sub-frame over the plasterboard around the wall opening. In some embodiments, the kink also defines a front surface against which a flange of the 5 doorset can be fitted. In some embodiments, the flange is a perforated flange. In some embodiments, the flange defines a bead that provides a guide surface for a 10 plasterer. In some embodiments, the sub-frame comprises two or more sub-frame components, each formed as a metal sheet. For example, the sub-frame may comprise four sub-frame components for defining a rectangular inner opening for a rectangular doorset. The 15 components may be two uprights or jambs, a lintel and a doorstep. Each may be at least 500mm long, and more preferably at least 800mm long. For example, two may have a length corresponding generally to the height of the doorset, whereas the other two may have a length corresponding generally to the width of the doorset (each preferably being slightly longer than the corresponding dimension of the doorset - e.g. 1 to 10cm longer). 20 In some embodiments the sub-frame components are matched in length to the door frame and corner pieces are used to connect between them in the corners - for example four corner pieces - one for each corner. The corner pieces can be used to ensure that the aperture is sufficiently larger than the vertical component and the horizontal 25 component to allow the doorset’s frame to fit therein. However, it may be made a tight fit as the corner pieces allow gaps between the frame and the sub-frame to remain minimal, thus avoiding undesirable gapping therebetween. In some embodiments, the metal sheet is a steel sheet. In others, it may be an aluminium 30 sheet. Aluminium has an advantage in that it can be more lightweight. However, it is less resilient to high temperatures, so preferably the metal is steel so that the installation system can be fire-rated to a higher specification. Preferably, the installation system is fire rated. For example, it may be certified for use as a fire or smoke door, certified, for example, to FD30, FD30S, FD60, FD60S, FD120, FD120S in the United Kingdom, or 35 E30, E30sa, E60, E60Sa, E120 and E120Sa in Europe, tested to the relevant Standard, 30 10 23 for example to BSEN1634-1 and / or BSEN1634-3, or to equivalent alternative national or regional Standards. In some embodiments, the sub-frame component is formed from a folded metal sheet. 5 In some embodiments, it may be an extruded section. Other forms of production may include fabrication, cold drawing, hot extrusion or hot rolling. Typically, however, the or each sub-frame component is made from just a single folded sheet of metal. 10 In some embodiments, the sub-frame can be formed from multiple separate such components, or multiple such components might be joined together to form the subframe. In some embodiments, the metal is steel. 15 In some embodiments, the section may be 1mm thick, 2mm thick, 3mm thick, or potentially 4mm thick. A preferred thickness is 1.2mm. In some embodiments, the foot part and the leg part form generally an L section - for 20 example with a right-angle bend or fold separating the two parts. This simple form is inexpensive to supply and can be oriented to provide the leg part against the underlying wall and the foot part with at least one surface extending generally parallel to the underlying wall for receiving the plasterboard there-against. 25 Screw holes or screw slots can be pre-drilled into the sub-frame, e.g. in the leg part of the or each component, as this makes it easier for a builder to attach the leg part to the underlying wall. In some embodiments, the steel is galvanised or painted to resist corrosion. 30 In some embodiments, the doorset has one or more door closure mechanism for biasing its door or doors towards to a closed position. In some embodiments, the doorset features an intumescent latch between the frame and 35 the or each door for securing a closed state of the door in the event of a fire. Usually the 30 10 23 intumescent latch is provided on a door-edge-facing surface of the frame. In the event of a fire, the intumescent latch - which may have an intumescent layer and a metal sheet overlying the intumescent layer - will expand or displace towards the edge of the door to retain it in a closed state. However, in some embodiments the intumescent latch is 5 instead provided on an edge of the door, facing the frame. Then, in the event of a fire, the intumescent latch will expand or displace towards the frame to retain the door in a closed state. It is also possible for intumescent latches to face both ways. A keep for the latch to expand into may be provided in an edge of the door to further 10 allow the latch to grip the door. By the intumescent latch being attached to the frame, the intumescent latch will then resist opening of the door due to the engagement of the intumescent latch in the keep. Such intumescent latches are available on the market. For example, Sera intumescent latches from the present applicant. 15 In some embodiments, multiple intumescent latches and keeps may be provided around the edge of the door. In some embodiments, the doorset is rectangular and the frame thereof comprises two uprights, or legs or jambs, a top member, or a head or lintel, and a doorstep, sill or 20 threshold. This simplifies the construction of the doorset and the sub-frame as the metal sheets can be longitudinally straight and cut to length to suit the doorset. For example, the sub-frame may then comprise four longitudinally straight metal sheets, one straight metal sheet for each side of the rectangle. This then further simplifies the installation thereof as the opening can be straight sided. 25 In some embodiments, the or each door is separately certified as a fire or smoke door, and / or the doorset is separately certified as a fire or smoke doorset, in each case preferably to at least a 60 minute, and more preferably a 90 minute or 2hr Standard, such as British Standard Certification FD60, FD60S, FD90 or FD90S, or more preferably 30 FD120 or FD120S. As before, in some circumstances other Certifications may be adequate, such as, for example, FD30, FD30S in the United Kingdom. For the latter, aluminium is likely fine as the structural material of the frame and door(s), but for the others steel is more likely the material of choice for the structural material of the frame and door(s). 30 10 23 Equivalent European Certifications are also suitable, such as E30, E30sa, E60, E60Sa, E120 and E120Sa, as would be others countries’ certifications for other markets. Ideally for the relevant standard the design of the door(s) or doorset will have been tested 5 and certified to the relevant Standard, for example to BSEN1634-1 and / or BSEN1634-3, or to equivalent alternative national or regional Standards. In some embodiments the frame is provided with a plurality of frame spacers for adjusting the position of the doorset within the sub-frame. 10 The frame spacers can be a bolt within a nut for adjustment through relative rotation of the bolt and nut. A foot of the bolt can engage against the sub-frame, and an opposite end of the bolt can 15 have a head for turning the bolt. For example, a hexagonal hole for an allen / hex key or a slot or crossed indentation for a screwdriver. The nut has a through-hole so that the bolt can be turned from within the nut. The nut thus may fit substantially flush to an inside surface of the frame, and the bolt may be 20 recessed relative thereto. In some embodiments, the flange is a laterally extending flange relative to the foot part. It thus may be as defined above with respect to the installation system. 25 In some embodiments, more than one such sub-frame component is provided. The present invention also comprises a kit of parts comprising a doorset with a frame and at least one door, and one or more sub-frame component as defined above for the installation system. The present invention thus provides a kit of parts comprising a 30 doorset and a sub-frame, wherein: the doorset comprises: i) a frame comprising a sidewall around its perimeter for extending into a wall opening and a laterally extending flange extending from the sidewall for engaging over a plasterboard sheet around the opening; and 35 ii) at least one door within the frame; and 30 10 23 the sub-frame comprises at least one sub-frame component in the form of a metal sheet having a length of at least 500mm, and having a substantially constant cross section, the cross section defining a leg part and a foot part when viewed in section, the foot part comprising a kink in its section to provide a step that defines a space into which 5 the plasterboard sheet will be fitted, and the leg part being for bridging a cavity between the plasterboard sheet and an underlying wall, the sub-frame extending around substantially all of the sidewall of the frame, and being for providing an inner opening inside the wall opening for receiving the doorset, wherein, upon installation of the doorset, the sidewall of the doorset extends into both the wall opening and the inner 10 opening, and the laterally extending flange of the frame extends from the sidewall in front of the sub-frame over the plasterboard around the wall opening. The sub-frame components can be used to form a sub-frame of the installation system as defined above. As such, the kit can be integrated into the installation system defined 15 above. The doorset may be as defined previously or as defined below. The present invention also provides a method of installing a doorset in a wall as defined 20 in claim 32 or claim 33, the wall comprising: a) a wall liner system comprising at least one plasterboard sheet; b) an underlying wall; c) a wall opening through both the underlying wall and the at least one plasterboard sheet; and 25 d) a cavity between the plasterboard sheet and the underlying wall; the method comprising: installing a sub-frame around the wall opening to bridge the cavity between the underlying wall and the plasterboard around substantially all of a perimeter of the wall opening, the sub-frame defining an inner opening inside the wall opening; and 30 installing a doorset into the inner opening, the doorset comprising: i) a frame comprising a sidewall around its perimeter for extending into the inner opening and a laterally extending flange extending from the sidewall for engaging over the plasterboard around the wall opening; and ii) at least one door within the frame; 30 10 23 wherein, upon said installation of the doorset, the sidewall of the doorset extends into both the wall opening and the inner opening, and the laterally extending flange extends from the sidewall in front of the sub-frame over the plasterboard around the wall opening. 5 The sub-frame may be a defined previously, or as defined below. The doorset may be as defined previously or as defined below. 10 The method may use the installation system, or a kit, as defined previously or as defined below. In some embodiments the method comprises adjusting the relative position of the doorset within the sub-frame by adjustment of one or more of a plurality of frame spacers. 15 In some embodiments the frame spacers are a bolt within a nut for adjustment through relative rotation of the bolt and nut. Preferably the nut is attached to the frame and the bolt extends into the nut. The nut may be a Hexsert (RTM) nut. 20 The nut may have a first end with a fixing flange for bearing against an inner surface of the frame to which it is installed. It may be welded to the frame. The first end may be hexagonal. The nut may have a second end in the form of a sleeve. The inside of the sleeve may be 25 threaded to receive a threaded shaft of the bolt. The bolt can have a foot that engages against the sub-frame, and an opposite end of the bolt can have a head for turning the bolt. The method comprises turning the bolt to either push the foot against the sub-frame to move that part of the frame away from that part 30 of the sub-frame, or it may retract the bolt to allow the frame to move closer to the subframe at that part thereof. The head may have a hexagonal hole for a hex key (Allen key) or a slot or crossed / star shaped indentation for a screwdriver. 30 10 23 The nut has a through-hole so that the head of the bolt can be turned from within the nut. The nut may fit substantially flush to an inside surface of the frame, and the bolt may be recessed relative thereto. 5 The method may additionally include a method of stabilising a doorstep of a doorset assembly in a wall, the method comprising: installing the sub-frame around the wall opening to bridge the cavity between the 10 underlying wall and the plasterboard sheet at least across the cavity at the bottom side of the wall opening, the sub-frame defining an inner opening inside the wall opening for receiving the doorset; fitting one or more leg under the sub-frame between the sub-frame and a floor component to support a leading edge of the sub-frame; and 15 installing the doorset into the inner opening. In some embodiments the leg is telescopic to allow its length to be adjusted to fit between the sub-frame and the floor component. 20 In some embodiments the floor component is a floorboard or a solid floor, such as a concrete floor. It might instead be a floor joist or some other structural part of the building situated just in front of, but underneath, the opening in the underlying wall. The leading edge of the sub-frame, without the leg, would merely be supported by 25 plasterboard in certain installation configurations, and it thus could tend to flex or bend if walked upon. With the leg supporting it, that tendency to flex or bend can be resisted, thus stabilising the doorstep. Typically, multiple legs would be installed. Preferably at least three, and more preferably 30 3 to 5. In some embodiments, the leg is attached to a stepped back surface of a foot part of the sub-frame. In some embodiments that stepped back part also defines a surface onto which the at least one plasterboard sheet is fitted. 30 10 23 The method of this final aspect may also be used with the method of the preceding aspect. Features of the sub-frame and the doorset of this final aspect may be as defined in 5 preceding aspects or below. These and other features of the present invention will now be described in further detail, purely by way of example, with reference to the accompanying drawings, in which: 10 Figure 1 shows a perspective view of a pair of doors of a doorset fitted with its frame installed in an opening in an underlying wall, omitting plasterboard and studs of a wall liner system surrounding the doorset for more clearly showing the invention; Figure 2 is a perspective view corresponding to Figure 1, but with the doorset also 15 omitted to show an underlying sub-frame and support legs; Figure 3 shows an enlarged view of a bottom right corner of Figure 2; Figure 4 shows a front elevation view of Figure 2 showing the sub-frame and support 20 legs installed in an opening in the underlying wall; Figure 5 shows a front elevation view of Figure 1 showing the doorset installed into the sub-frame of Figure 4; 25 Figure 6 shows an enlarged view of a bottom right corner of Figure 1, with perforated flanges of the doorset covering a top part of the support legs and overlapping laterally extending feet of the sub-frame; Figure 7 shows a side elevation view of Figure 4, showing the feet and support legs to 30 be spaced away from the underlying wall; Figure 8 shows an enlarged view of a top portion of the sub-frame from Figure 7; Figure 9 shows an enlarged view of a bottom portion of the sub-frame and one of the 35 support legs from Figure 7; 30 10 23 Figure 10 shows a more detailed view of a foot of an upper part of the sub-frame, detailing a circled area of Figure 8 5 Figure 11 shows a more detailed view of a foot of a lower part of the sub-frame, and one of the support legs, detailing a circled area of Figure 9, and a possible connection of the one of the support legs to that foot; Figure 12 shows a side elevation view of Figure 5; 10 Figure 13 shows an enlarged view of a top portion of the sub-frame and doorset from Figure 12; Figure 14 shows an enlarged view of a bottom portion of the sub-frame, support leg and 15 doorset from Figure 12, with a modified depth for the support leg versus that of Figure 11; Figure 15 shows a more detailed view of a circled area of Figure 13 showing the foot of the upper part of the sub-frame, similar to Figure 10, but additionally detailing parts of 20 the doorset that is installed in the sub-frame; Figure 16 shows a more detailed view of a circled area of Figure 14 showing a foot of a lower part of the sub-frame, and one of the support legs, similar to Figure 11, but additionally detailing the modified support leg’s depth, and parts of the doorset that is 25 installed in the sub-frame; Figures 17 to 21 show one of the support legs prior to installation, with Figures 17 and 18 being mirrored perspective views from front and back right sides of the support leg, Figure 19 being a top-down plan view, Figure 20 being a right-side elevation view and 30 Figure 20 being a front elevation view; and Figures 22 to 25 show an optional frame spacer that can be incorporated into the subframe, or as shown into the frame of the doorset, for adjusting the relative position of, respectively, the sub-frame to the underlying wall, or the frame to the sub-frame, for 30 10 23 example to allow centralisation or levelling of the sub-frame or frame within, respectively, the underlying wall or the sub-frame. Referring first of all to Figure 1, a doorset 12 can be seen installed within an opening in 5 an underlying wall. The doorset 12 comprises two doors 10 and a frame 14. Some doorsets 12 will instead feature just a single door 10. The frame 14 has a perforated flange 24 around its perimeter. The perforated flange is perforated for better keying-in of plaster: - when plasterboard 124 is fitted over the 10 underlying wall 18, for example using a wall liner system as known in the art, the perforated flange 24 will sit over an outer surface of the plasterboard 124 (where it is cut away around the opening), and a skim of plaster will be applied over the plasterboard 124 and the perforated flange 24 to provide a flat surface for any final surface covering, such as paint, wall paper, or wall tiles. For this purpose, the perforated flange 24 may 15 have a bead 34 at its inner edge (relative to an outer shape of the frame) to which the plasterer can work for a neat finish. The bead 34 can be best seen in Figures 15 and 16. In this embodiment, the doors 10 are fitted flush to that bead 34 so that the finished wall (with plaster and the installed doorset 12 with its doors 10) has a minimalist appearance 20 - usually with no architrave around the doors 10, and thus presenting effectively just a flat surface with a minimal visibility for the doors 10 - perhaps just a gap 38 between the frame 14 and the doors 10, and between the doors 10 themselves, when more than one is provided in the doorset 12, and an optional latch 36. 25 Referring next to Figure 2, the installation is again shown in perspective, but in its condition prior to installation of the doorset 12 (or with the doorset 12 removed) so that a sub-frame 20 of an installation system of the present invention can be better seen. The sub-frame 20 in this embodiment comprises four generally L sectioned components: 30 two uprights or jambs 48, a lintel 46 and a doorstep 50. These four components are generally straight along their lengths and the L shape of their sections provides them with sufficient stiffness to be self-supporting. The L section defines a leg part 30 and a foot part 28. 30 10 23 During installation of the installation system, the leg part 30 of each component is screwed to the underlying wall 18 using long screws. For this purpose, holes 42 or slots 44, or both, can be intermittently positioned along the lengths of the components, as shown. All four of the leg parts 30 extend longitudinally through the opening, so as to 5 define a uniform opening within the opening in the underlying wall. In this embodiment, the uniform opening has two pairs of parallel sides - to the sides, and top and bottom, as the doorset 12 is rectangular doorset 12. The components 46, 48, 50 can be of a suitable shape and number for facilitating the installation of the doorset in the uniform opening defined therein, once attached to the underlying wall. The opening in the 10 underlying wall 18 is likewise suitably sized to accommodate the components 46, 48, 50 of the sub-frame 12, but does not need to be as uniform around those components as the uniform opening defined by those components. One or more intumescent strip may extend the length of the components 46, 48, 50 15 between the respective component 46, 48, 50 and the underlying wall 18 to offer a fire or smoke resistant seal or closure between the component and the wall in the event of a fire. The intumescent strips, in their unexpanded form, can at least partially bridge the gap between the outside of the components and the underlying wall, although given the lesser need for uniformity, there may still remain some gaps there-between. Upon 20 exposure to a triggering heat from a fire, the intumescent strips can expand to close or substantially close any remaining gaps. As an alternative, or in addition to such intumescent strips, intumescent acrylic sealant or intumescent foam may be used to seal or close the gap between the sub frame and 25 the wall. As the leg parts 30 of the components 46, 48, 50 extend longitudinally, i.e. extending perpendicular to the face of the plasterboard 124, they bridge any longitudinal gap between the plasterboard 124 and the underlying wall 18 (i.e. the gap extending 30 perpendicular to the face of the plasterboard 124), once installed in the opening in the underlying wall 18 (i.e. once the wall liner system is also installed). Upon expansion of the intumescent strips the intumescent strips also close any remaining lateral gap between the sub-frame 20 and the underlying wall 18 (i.e. parallel to the back of the plasterboard 124). This sub-frame 20 thus provides a more efficient barrier to smoke and 35 fire through any gap that lies adjacent to the underlying wall compared to prior art 30 10 23 installation techniques, as it substantially eliminates the gap that would otherwise be present between the frame 14 of the doorset 12 and the underlying wall 18. The intumescent strip further improves that barrier. 5 The doorstep 50 of this sub-frame 20 is in this embodiment spaced above the floor 40 of the room. It sits on the underlying wall 18 and is screwed thereto using the holes 42 and slots 44, but because the leg part 30 extends to the foot part 28, which foot part 28 is spaced away from the underlying wall 18, there can be a significant bending moment applied to this doorstep 50 in the event that someone steps on the doorstep 50 near its 10 foot part 28. This can create twisting of the sub-frame 20, especially if each component 46, 48, 50 of the sub-frame 20 is not joined together at the corners of the sub-frame 20. In some embodiments they might be joined, but normally, for ease of installation, they won’t be, and they are supplied as separate components. To resist that twisting, support legs 22 are provided to bridge between the foot parts 28 and the floor 40. These support 15 legs are telescopic in this embodiment, as will be described later, to allow a range of heights above the floor 40 to be accommodated. By virtue of these support legs, which can be fixed to the foot part 28 of the doorstep 50, and also to the floor 40, they can resist the bending moment to prevent twisting of the door step 50. These support legs 22 thus stiffen the installation, making it more durable. 20 Such support legs are not needed for the sides (uprights or jambs 48) or the lintel 46 as they will not be walked upon, and thus will not be exposed to the same degree of loading. Referring next to Figure 3, the holes 42 and the slots 44 in the leg part of the doorstep 25 50 for screwing the doorstep 50 to the underlying wall 18 are more clearly shown. Furthermore, the support legs 22 can be seen to be attached - for example with self tapping screws or rivets 52 - to the foot part 28 of the doorstep 50, and a bottom of the support legs 22 can be seen to be screwed down to the floor 40 with screws 54 via flanges 56 of a lower part 58 of the support legs 22. 30 Figures 4 and 5 show in front elevation views the sub-frame 20 in an opening in the wall 18, onto which the support legs are then installed (and to the floor 40) and then the doorset 12 is installed in the sub-frame. 30 10 23 The doorset can be a pre-assembled unit, with doors 10 pre-fitted, which doors may need to be removed to allow the frame 14 of the doorset 12 to be installed to the sub-frame 20 using self-tapping screws. 5 As the frame and the sub-frame are both preferably made of steel - usually painted steel - self tapping-screws are the preferred mechanism for joining them together. They are not shown as they are obscured by the doors 10. Figure 6 shows in more detail a corner of the installation, showing how the perforated 10 flanges 24 of the frame 14 cover the top of the support legs, trapping the support legs between the perforated flange 24 and the foot part 28 of the doorstep 50. This offers additional stiffness and strength / durability to the installation as the support legs 22 are resisted from releasing their connection to the foot part 28. 15 Referring next to Figures 7 to 11, side views of the sub-frame installation is shown, prior to installation of the doorset 12. As can be seen, the top end of the sub-frame installation (Figures 8 and 10) has in side profile the leg part 30 of the lintel 46, which extends generally horizontally, and which in this embodiment is a flat sheet across the top of the opening. It also has the foot part 28 of the lintel 46, which in this embodiment has three 20 segments. There is a first segment 60 bent at 90 degrees upwards from the leg part 30, followed by a middle segment 62 that is bent 90 degrees from the first segment 60 into a position over the top of and parallel to the leg part 30, and finally a third segment 64 that is bent at 90 degrees to the middle segment 62, to lie there-above and parallel to the first segment 60. These three segments 60, 62, 64 define the foot part 28, which 25 relative to the leg part 30, form a generally L-shaped section for the lintel 46. The section of the two uprights 48 and the doorstep 50 correspond to that of the lintel 46, albeit with the doorstep 50 mirroring the lintel (so that the foot part 28 extends downwards, rather than upwards) and with the uprights or jambs 48 having their foot 30 parts 28 extending sidewards (each being mirrored to one another by extending outward relative to the respective leg parts 30). Due to the stepped form of the foot parts 28, as provided by the three segments 60, 62, 64, the foot parts 28 provide a rearwardly extending shoulder or step to define a space 35 into and / or onto which plasterboard 124 of a wall liner system can be installed. 30 10 23 The rearwardly extending shoulder or step is preferably of a depth to accommodate the thickness of standard plasterboard 124 so that once the plasterboard 124 is installed, it sits against the third segments 64 and generally flush with the first segment 60. For walls, 5 plasterboard 124 is usually between 12.5mm and 15mm thick, so it is preferred that the step has a depth of between 13mm and 15.5mm, or more preferably about 15.5mm (or 15 to 16mm) to accommodate the whole usual range of thicknesses of conventional walluse plasterboard 124. By being slightly deeper than the thickness of the plasterboard 124, the plasterboard 124 will still fit even if it has surface irregularities. 10 The support legs 22 likewise sit in or on the space provided by the shoulder or step, but attach to the third segment 64. In this embodiment, the upper ends of the support legs 22 are spaced downward from the middle segment 62. However, they can instead be butted up against the middle segment 62. 15 As shown in Figures 9 and 11, the support leg 22 may be thicker than the depth of the step, although as shown in Figure 14, it is preferred to have the same thickness as the depth of the step. This then allows the perforated flange 24 of the doorset 12 to fit there-against, rather than needing to be cut around the support legs 22. 20 Referring next to Figures 12 to 16, the doorset 12 has now been fitted to the sub-frame of Figure 7. As a result, the perforated flange 24 and the bead 34 can now be seen in the side views. Referring to Figure 13, which shows the top part of the installation, the bead is visible from the sides of the frame, and only visible along the corner of the top 25 part of the frame (corresponding to the lintel). A top of a hinge pin 66 is also visible. This is shown with more details in Figure 15. Referring to Figure 15, which is a sectional view, the hinge pin extending through the lintel 46 is visible. It extends from the door 10. Figure 15 also shows the gap 38 between 30 the door and the frame 14. It also shows how the frame 14 fits against the first segment 60 of the foot part 28 of the sub-frame, but is spaced from the leg part 30. This spacing allows a tolerance for the fitting of the sub-frame to the underlying wall 18 as the perforated flanges can accommodate a relatively wide gap - perhaps up to 20mm - by covering over it and still bearing against the first segment 60 of the foot part 28, and thus 35 giving a clean wall finish even if the opening in the wall 18 has sufficiently no straight 30 10 23 sides to cause the sub-frame 20 to bend slightly when it is being screwed to the underlying wall 18. As can also be seen in Figure 15, the front of the door 10 is flush with the bead 34. This 5 ensures when plaster is applied to the perforated flange 24 and the plasterboard 124 of the wall liner system (only the plasterboard 124 of which is shown in Figures 4 and 15) the or each door 10 will be flush to the plaster - as the plaster is applied up to the bead 34. 10 Various other features of the doorset 12 are also shown, such as a draft-proofing or smoke sealing strip 68 that is applied to a door stop of the frame - against which the door 10 will bear when in their closed state, and a door closure mechanism 70 for defaulting the doors 10 into their closed state. 15 This illustration also shows an intumescent latch 72 at the door’s edge, which intumescent latch 72 comprises a metal strip 74 with an underlying intumescent strip 76, which intumescent strip 76 can expand in a fire to bias the metal strip 74, or a part thereof, into a keep (not shown) on the door 10. 20 Referring next to Figure 16, this is similar to the top, in that it has the intumescent latch 72, the draft proofing or smoke sealing strip 68, and the door stop 78, but in place of the door closing mechanism, an automatic draft excluding mechanism 80 is fitted to the rear of the door 10. 25 Door closure mechanisms 70 and automatic draft excluding mechanisms 80 are known in the art and thus will not be further described herein and are only partially shown in schematic form. Figure 16 also additionally shows the support leg 22, as previously discussed. As shown, 30 in this figure, the perforated flange 24 sandwiches the support leg 22 against the third segment 64 of the foot part 28 of the sub-frame’s doorstep 50. Referring next to Figures 17 to 21, a preferred design for the support legs 22 is shown. This design is a telescopic arrangement that can be set and locked at a desired height -35 for example during installation of the doors / frames / sub-frames. For that purpose, the 30 10 23 support leg 22 comprises the lower part 58 which fits inside an upper part 82. The upper part 82 defines a groove or slot 84 in its rear into which a shaft 94 of the lower part 58 fits, which shaft and groove, in this embodiment, are generally rectangular. Other shapes and forms are possible as well, as well known for telescopic arrangements, including an 5 enclosing tube, rather than just a groove, for the upper part 82. At the bottom of the shaft 94, the flanges 56 extend laterally, and each is provided with a hole 92 for the screws that affix the support leg 22 to the floor 40. 10 The sides of the upper part also have flanges 86 extending therefrom. These are provided with holes 88 towards their tops for receiving self-tapping screws or rivets 52 for attaching the support leg 22 to the third segment 64 of the doorstep’s foot part 28. Finally, the upper hart has self-tapping screws 90 extending through the side and through 15 the shaft 94 too, to lock the length of the support leg 22. These bolts - two in this embodiment - may be fitted through pre-drilled holes in the upper part 82 from either side of the upper part. As shown, pre-drilled holes 96 are shown in the other side in case it would have been easier to install the self-tapping screws 90 there instead. 20 Figure 19 shows the support leg 22 from above, and thus clearly shows the screws 90 extending through both the upper and lower parts 58, 82. Figures 20 and 21 show further images of the support leg for further illustrating its configuration in this preferred embodiment. As shown, in this design the upper and lower 25 parts 58, 82 can both be formed by pressing sheet steel, as they are both open at the back and simply formed by folding the steel sheet in the illustrated form. Referring finally to Figures 22 to 25 there is shown an optional frame spacer 32 that is incorporated into the frame 14 of the doorset 12 for adjusting the relative position of the 30 frame 14 to the sub-frame 20, for example to allow centralisation or levelling of the frame 14 within sub-frame 20. In practice, an installed sub-frame 20 (or the opening in the underlying wall 18) will not be perfectly rectangular, and it will not perfectly fit with respect to the frame 14 of the 35 doorset 12. There will thus be a certain gap at least in places around the perimeter of 30 10 23 the frame 14 with respect to the sub-frame 20 (or between the sub-frame and the underlying wall. To allow for this irregularity, during the installation of a frame 14 into a sub-frame 20, a possible approach would be to use wedges or plastic spacers between the frame 14 and the sub-frame 20 and to adjust them - or to add or remove more of 5 them, while using a spirit level on the frame 14, until the frame sits correctly level and in the desired position with respect to the underlying wall - or more likely the plasterboard 124 of the wall liner system. Only then is the frame 14 locked in that restrained position with self-tapping screws that pass through the frame and the sub-frame. The wedges and plastic spacers will commonly then be left in situ too, after that fixation, to maintain 10 a firm installation condition. However, the use of such wedges and plastic spacers can be particularly frustrating as they tend to fall out when moving the frame - for example to better level it, or to better position it flush to or against the plasterboard 124 of the wall liner system. Such an installation of the frame 14 can thus be a two-man job - with someone on the spirit level and self-tapping screws for locking the frame in place once 15 level, and someone on the wedges and spacers to ensure they stay in place (and that the frame likewise stays in place). Perhaps each person will be on different sides (front and back) of the frame 14, or with a double door arrangement as shown to a left and right side of the frame 14. Alternatively, as a one-man job it can take a long time to get right. This is a viable mode of installation of the present invention. However, in 20 accordance with another aspect of the present invention, the doorset can be provided with pre-installed frame spacers 32, which can better or quicker facilitate the alignment and retention of that alignment of the frame 14 in the sub-frame 20. This is achieved since the frame spacers 32 as illustrated in the embodiment of Figure 22, cannot fall out during manipulation of the frame 14 relative to the sub-frame 20 as they are attached to 25 the frame 14. However, they are also adjustable to allow them to be lengthened or shortened as necessary to push against or to retract from the sub-frame 20, whereby an installer can easily find a level for the frame 14 using a spirit level, without having to think about whether the wedges or plastic spacers are about to fall out. 30 In this embodiment, the doorset has reinforced corners 100 as it is designed to be preassembled and relatively stiff, so that it can be quickly installed and then be immediately ready for use as the doors are pre-fitted as well. With this version of the present invention, the frame spacers 32 can be adjusted to push 35 against or release from the sub-frame 20 to manoeuvre the frame 14 relative to the sub 30 10 23 frame, i.e. closer to it by retracting a bolt part 118 thereof away from the sub-frame 20 or further therefrom by driving the bolt part 118 towards the sub-frame 20. Figure 22 is a cut-away view showing the frame spacer 32 arranged perpendicular 5 (laterally extending) relative to the longitudinal axis of the doorset, i.e. out to the side thereof. The frame spacer 32 comprises two parts - a nut part 120 attached to the frame 14 and the bolt part 118 that screws therein and extends laterally therefrom with respect to the doorset 12. 10 The bolt part 118 is shown separate therefrom in Figures 24 and 25. As can be seen the bolt part 118 comprises a threaded shaft 106 and a foot 102 at a first end, and a head 112 with a hexagonal hole 114 at the other end. In this embodiment, the foot 102 has a larger diameter than the shaft. This serves to restrict the amount the bolt part 118 can be screwed into the nut part 120. 15 Referring then to Figure 23, the nut part 120 is a hexagonal insert, such as, or similar to, a Hexsert (RTM) by Advel (RTM). It has a hexagonal first end 104 with a fixing flange 122 for bearing against the surface to which it is installed (e.g. it can be welded to the frame 14). The hexagonal first end 104 then leads to a sleeve 116 at the other end. The 20 inside of the sleeve 116 is threaded 108 to receive the threaded shaft 106 of the bolt part 118. The hexagonal first end 104 need not be hexagonal as it is affixed to the frame 14 and thus will be resisted from rotation relative thereto, whereby rotation of the bolt part 118 25 will drive the bolt part 118 in and out relative to the sleeve 116. The hexagonal first end, however, due to the flat surfaces, will tend to be easier to fit to the frame in a manner that resists rotation thereof relative to the frame - e.g. by installing it in a hexagonal hole. To allow adjustment of the bolt part 118 from the opening in the frame 14 in which the doors 10 fit, the end of the nut part 120 with the fixing flange 112 is accessible at that 30 opening in the frame. Furthermore it has a hole 110 therein that extends through to the threaded sleeve 116. That hole 110 is larger than the hexagonal hole 114 in the bolt part 118 and thus allows an Allen key or the like to be used to adjust the bolt part 118 by rotation relative to the nut part 120. The bolt part 118 can thus be turned to move it relative to the frame into and out of engagement with the sub-frame 20, or for bearing 35 against the sub-frame 20 to adjust the relative position of the frame 14 and the sub-frame 20. The frame 14 can thus easily be adjusted to assume a level condition within the subframe 20. As discussed above, similar frame spacers may be supplied for the sub-frame for 5 adjusting it relative to the underlying wall, which can be more appropriate if the sub-frame is a one-piece structure. However, in preferred embodiments, the sub-frame 20 is formed of multiple components 46, 48, 50, and thus the use of equivalent frame spacers 32 for the sub-frame 20 is less likely to be helpful. 10 The present invention has therefore been described above, purely by way of example. Modifications in detail may be made to the invention within the scope of the claims as appended hereto. 30 10 23 30 10 23

Claims

1. An installation system for installing a doorset in a wall,the wall featuring:5 a) a wall liner system comprising at least one plasterboard sheet;b) an underlying wall;c) a wall opening for the installation system through both the underlying wall and the at least one plasterboard sheet; andd) a cavity between the plasterboard sheet of the wall liner system and the 10 underlying wall;and the installation system comprising a doorset and a sub-frame, wherein:the doorset comprises:i) a frame comprising a sidewall around its perimeter for extending into the wall opening and a laterally extending flange extending from the sidewall for engaging 15 over the plasterboard around the wall opening; andii) at least one door within the frame; andthe sub-frame comprises at least one sub-frame component in the form of a metal sheet having a length of at least 500mm, and having a substantially constant cross section, the cross section defining a leg part and a foot part when viewed in section, the 20 foot part comprising a kink in its section to provide a step that defines a space into which the plasterboard will be fitted, and the leg part being for bridging the cavity between the underlying wall and the plasterboard, the sub-frame extending around substantially all of the sidewall of the frame, and being for providing an inner opening inside the wall opening for receiving the doorset, wherein, upon installation of the doorset, the sidewall 25 of the doorset extends into both the wall opening and the inner opening, and the laterally extending flange of the frame extends from the sidewall in front of the sub-frame over the plasterboard around the wall opening.

2. The installation system of claim 1, wherein the kink defines a front surface against 30 which the flange of the doorset can be fitted.

3. The installation system of any one of the preceding claims, wherein the flange is a perforated flange.30 10 234. The installation system of any one of the preceding claims, wherein the flange defines a bead that provides a guide surface for a plasterer.

5. The installation system of any one of the preceding claims, wherein the sub-frame 5 comprises two or more sub-frame components, each formed as a metal sheet.

6. The installation system of claim 5, wherein the sub-frame comprises four subframe components for defining a rectangular inner opening for a rectangular doorset.10 7. The installation system of any one of the preceding claims, wherein the or eachsub-frame component has a length corresponding generally to, or being longer than, a height or width of the doorset.

8. The installation system of any one of the preceding claims, wherein the metal 15 sheet is a steel sheet.

9. The installation system of any one of the preceding claims, wherein the installation system is fire rated.20 10. The installation system of any one of the preceding claims, wherein theinstallation system is certified for use as a fire or smoke door.

11. The installation system of claim 9 or claim 10, wherein the installation system is certified to the FD30, FD30S, FD60, FD60S, FD120 or FD120S standard in the United25 Kingdom, or the E30, E30sa, E60, E60Sa, E120 or E120Sa standard in Europe.

12. The installation system of any one of the preceding claims, wherein the sub-frame component is formed from a folded metal sheet.30 13. The installation system of any one of the preceding claims, wherein the foot partand the leg part form generally an L section.

14. The installation system of any one of the preceding claims, wherein a right-angle bend or fold separates the leg part from the foot part.30 10 2315. The installation system of any one of the preceding claims, wherein the foot part has at least one surface extending generally parallel to the underlying wall for receiving the plasterboard sheet there-against.5 16. The installation system of any one of the preceding claims, wherein screw holesor screw slots are pre-drilled into the sub-frame.

17. The installation system of claim 16, wherein the screw holes or screw slots are in the leg part of the or each sub-frame component for screwing the leg part to the 10 underlying wall.

18. The installation system of any one of the preceding claims, wherein the metal is galvanised steel or painted.15 19. The installation system of any one of the preceding claims, wherein the doorsethas one or more door closure mechanism for biasing its door or doors towards to a closed position.

20. The installation system of any one of the preceding claims, wherein the doorset 20 features at least one intumescent latch between the frame and the or each door for securing a closed state of the door in the event of a fire.

21. The installation system of claim 20, wherein the intumescent latch has an intumescent layer and a metal sheet overlying the intumescent layer.2522. The installation system of any one of the preceding claims, wherein the doorset is rectangular and the frame thereof comprises two uprights, or legs or jambs, a top member, or a head or lintel, and a doorstep, sill or threshold, and the sub-frame comprises four longitudinally straight metal sheets, one straight metal sheet for each side 30 of the rectangle.

23. The installation system of any one of the preceding claims, wherein the frame isprovided with a plurality of frame spacers for adjusting the position of the doorset within the sub-frame.30 10 2324. The installation system of claim 24, wherein the frame spacers comprise a bolt within a nut for adjustment through relative rotation of the bolt and nut.

25. The installation system of claim 23 or claim 24, wherein a foot of the bolt engages against the sub-frame and an opposite end of the bolt has a head for turning the bolt.

26. The installation system of claim 25, wherein the nut has a through-hole so that the bolt can be turned from within the nut.

28. A kit of parts comprising a doorset with a frame and at least one door, and at least one sub-frame component of the doorset installation system of any one of the preceding claims, the sub-frame component comprising a metal sheet having a length of at least 500mm, and having a substantially constant cross section, the cross section defining a leg part and a foot part when viewed in section, the leg part being for bridging a cavity in a wall and the foot part being for receiving a plasterboard sheet of the wall there-against, wherein the foot part comprises a kink in its section to provide a step that defines a space into which the plasterboard sheet will be fitted, andthe doorset comprises:i) a frame comprising a sidewall around its perimeter for extending into a wall opening and a laterally extending flange extending from the sidewall for engaging over a plasterboard sheet around the opening; andii) at least one door within the frame; andthe leg part being for bridging a cavity between the plasterboard sheet and an underlying wall, the sub-frame extending around substantially all of the sidewall of the frame, and being for providing an inner opening inside the wall opening for receiving the doorset, wherein, upon installation of the doorset, the sidewall of the doorset extends into both the wall opening and the inner opening, and the laterally extending flange of the frame extends from the sidewall in front of the sub-frame over the plasterboard around the wall opening.

29. The kit of parts of claim 28, wherein wherein the flange is a laterally extending flange relative to the foot part.

30. The kit of parts of claim 28 or claim 29, comprising more than one sub-frame component.30 10 2331. The kit of parts of any one of claims 28 to 30, being integrated into the installation system of any one of claims 1 to 27.5 32. A method of installing a doorset in a wall using the installation system of any oneof claims 1 to 27, the wall comprising:a) the wall liner system comprising the at least one plasterboard sheet;b) the underlying wall;c) the wall opening through both the underlying wall and the at least one 10 plasterboard sheet; andd) the cavity between the plasterboard sheet and the underlying wall;the method comprising:installing the sub-frame around the wall opening to bridge the cavity between the underlying wall and the plasterboard around substantially all of the perimeter of the wall 15 opening, the sub-frame defining the inner opening inside the wall opening; andinstalling the doorset into the inner opening, the doorset comprising:i) the frame comprising the sidewall around its perimeter for extending into the inner opening and the laterally extending flange extending from the sidewall for engaging over the plasterboard around the wall opening; and20 ii) the at least one door within the frame;wherein, upon said installation of the doorset, the sidewall of the doorset extends into both the wall opening and the inner opening, and the laterally extending flange extends from the sidewall in front of the sub-frame over the plasterboard around the wall opening.2533. A method of installing a doorset in a wall using the kit of parts of any one of claims 28 to 31, the wall comprising:a) the wall liner system comprising the at least one plasterboard sheet;b) the underlying wall;30 c) the wall opening through both the underlying wall and the at least oneplasterboard sheet; andd) the cavity between the plasterboard sheet and the underlying wall;the method comprising:30 10 23installing the sub-frame around the wall opening to bridge the cavity between the underlying wall and the plasterboard around substantially all of the perimeter of the wall opening, the sub-frame defining the inner opening inside the wall opening; andinstalling the doorset into the inner opening, the doorset comprising:5 i) the frame comprising the sidewall around its perimeter for extending intothe inner opening and the laterally extending flange extending from the sidewall for engaging over the plasterboard around the wall opening; andii) the at least one door within the frame;wherein, upon said installation of the doorset, the sidewall of the doorset extends 10 into both the wall opening and the inner opening, and the laterally extending flange extends from the sidewall in front of the sub-frame over the plasterboard around the wall opening.

34. The method of claim 32 or claim 33, comprising adjusting the relative position of 15 the doorset within the sub-frame by adjustment of one or more of a plurality of frame spacers.

35. The method of claim 34, wherein the frame spacers are a bolt within a nut for adjustment through relative rotation of the bolt and nut.2036. The method of claim 35, wherein the nut has a first end with a fixing flange for bearing against an inner surface of the frame to which it is installed.

37. The method of claim 35 or claim 36, wherein the nut is welded to the frame.2538. The method of any one of claims 35 to 37, wherein the nut has a second end in the form of a sleeve, the inside of the sleeve being threaded to receive a threaded shaft of the bolt.30 39. The method of any one of claims 35 to 38, wherein the bolt has a foot thatengages against the sub-frame, and an opposite end of the bolt has a head for turning the bolt, the method comprising turning the bolt to either push the foot against the subframe to move that part of the frame away from that part of the sub-frame, or to retract the bolt to allow the frame to move closer to the sub-frame at that part thereof.30 10 2340. The method of any one of claims 32 to 39, further comprising stabilising a doorstep of the doorset in the wall;the method comprising:installing the sub-frame around the wall opening to bridge the cavity between the5 underlying wall and the plasterboard sheet at least across the cavity at the bottom side of the wall opening, the sub-frame defining the inner opening inside the wall opening for receiving the doorset;fitting one or more leg under the sub-frame between the sub-frame and a floor component to support a leading edge of the sub-frame; and10 installing the doorset into the inner opening.

41. The method of claim 40, wherein the leg is telescopic to allow its length to be adjusted to fit between the sub-frame and the floor component.15 42. The method of claim 40 or claim 41, wherein the floor component is a floorboardor a solid floor, such as a concrete floor.

43. The method of any one of claims 40 to 42, wherein at least three legs are fitted under the sub-frame between the sub-frame and the floor.2044. The method of any one of claims 40 to 43, wherein the leg is attached to a stepped back surface of a foot part of the sub-frame.

45. The method of claim 44, wherein that stepped back part also defines a surface 25 onto which the at least one plasterboard sheet is fitted.

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