Spacer, method, and system for providing a drainage gap

Abstract

A cavity drain spacer and method of providing a drainage gap between a substantially planar member (10 fig. 1) and a substrate (20 fig. 1). The method comprises securing a plurality of spacers 100A to

Description

FIELD OF THE INVENTION Embodiments of the present invention relate to a spacer, a method, and a system for providing a drainage gap in construction. In particular, but not exclusively, they relate to a cavity drain installation method of providing a drainage gap between a substantially planar member and a substrate, and they relate to a cavity drain spacer for use with the method. BACKGROUND TO THE INVENTION A cavity drain system, often used in the construction and waterproofing of basements and below-ground structures, is a type of waterproofing method. It consists of a network of channels or cavities within the structure's walls and floors, designed to manage and redirect water that penetrates through the building envelope. Unlike traditional tanking methods that try to seal out water, a cavity drain system allows water to enter but controls it by directing it to drainage points, such as sumps and pumps. The collected water is then safely removed from the structure. This approach is considered more flexible and reliable for long-term waterproofing and is often used in situations where preventing water infiltration is challenging or expensive. A cavity drain membrane is sheet component used in cavity drain systems. Its primary role is to provide a physical barrier against water ingress while allowing for controlled water management. The membrane is placed in the gap between a ground-retaining wall and an interior wall, or between a floor slab and an overlying floor structure. Cavity drain membranes generally consist of a sheet supporting an array of protruding egg-cup profiles, which creates a permanent gap acting as a drainage channel. Cavity drain membranes are the generally-accepted product for providing a drainage channel, and are described in the relevant British Standard 8102:2022 However, the present disclosure considers that cavity drain membranes have drawbacks. Firstly, condensation can occur on the internal side of the cavity drain membrane (facing into the room), especially when insulation is applied on as a further layer. Secondly, cavity drain membranes are fixed to the underlying substrate by piercing plugs, which break the watertight seal or any underlying waterproofing layers. A solution which is generally considered satisfactory is to use specially-adapted plugs that comprise an integrated sealing washer. However, the quality of the seal may be imperfect and further depends on the skill and precision of the installation worker. BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. According to various, but not necessarily all, embodiments of the invention there is provided a method of providing a drainage gap between a substantially planar member and a substrate, the method comprising: securing a plurality of spacers to the substantially planar member or the substrate via a retaining means (“retainer”), each spacer comprising a first end facing the substantially planar member or substrate to which the spacer is secured, a second end opposite the first end, and a cavity having an opening at the second end or at each end; filling the cavity of each spacer with a settable adhesive, the cavity being overfilled to cause a portion of the settable adhesive to protrude from the spacer at the second end; and pressing the substantially planar member against the substrate to allow the settable adhesive to bond with at least the other of the substantially planar member or substrate. An advantage is a more effective and reliable water drainage system. This is because the plurality of separate spacers ensure that the drainage gap is a mostly empty void of the minimum prescribed thickness, enabling any water entering the drainage gap to drain freely. As part of a cavity drain system, the spacers do not have the above-described disadvantages of cavity drain membranes described above. According to various, but not necessarily all, embodiments of the invention there is provided a spacer (e.g., “cavity drain spacer”), dimensioned to provide a drainage gap between a substantially planar member and a substrate, the spacer comprising a first end, a second end, a retaining means (“retainer”) for securing the spacer to the substantially planar member or the substrate with the first end facing the substantially planar member or substrate, and the spacer further comprising a cavity having at least an opening at the second end or at each end and which is fillable by a settable adhesive for securing the spacer to at least the other of the substantially planar member or the substrate. According to various, but not necessarily all, embodiments of the invention there is provided a spacer comprising a first end, a second end, a retaining means for securing the spacer to a surface, and a cavity having an opening at the second end or at each end. According to various, but not necessarily all, embodiments of the invention, there is provided an apparatus comprising the spacer, and the settable adhesive which fills the cavity. According to various, but not necessarily all, embodiments of the invention there is provided a system comprising a plurality of the spacers. Optionally, the system may further comprise the substantially planar member. The spacers may be secured or securable to the substantially planar member or the substrate by the retaining means. The below statements refer to optional features that can be combined with any one of the above statements. The below statements refer to the optional features of a single spacer. If multiple spacers are provided, each spacer may comprise said optional feature. The spacer may be a building construction spacer. The spacer may be a cavity drain spacer. The substantially planar member may be a slab or panel. The substrate may be a wall or floor slab. For example, the substantially planar member may be a board. The substrate may be a wall, a floor slab, or a frame secured thereto. In specific examples, the substantially planar member may be a board in the form of an insulation board. The substrate may be an earth retaining wall or a floor slab. The method may be a cavity drain installation method. The settable adhesive may comprise a cream, paste or foam adhesive. According to some, but not all examples, the cavity of the spacer comprises the opening at the second end and also a further opening at the first end of the spacer, the cavity being a through-hole between the first and second ends of the spacer enabling the settable adhesive to bond with both the substantially planar member and the substrate. An advantage is a strong bond because the settable adhesive directly bonds the substantially planar member to the substrate, through the cavity. The filling and pressing steps of the above method may therefore cause the settable adhesive to simultaneously bond with the substantially planar member and substrate through the openings. The step of pressing the substantially planar member against the substrate may be performed while the settable adhesive in each spacer is still in an uncured liquid state, enabling the settable adhesive to further bond to the substrate. Since the settable adhesive is still substantially uncured during the above steps, the spacer would potentially slide or fall off the substantially planar member while the substantially planar member is manoeuvred into a position for pressing against the substrate, if not for the separate retaining means which further secures the spacer to the substantially planar member. The retaining means may comprise one or more piercing members and / or a further adhesive, to secure the spacer to the substantially planar member or the substrate. The retaining means may be located at the first end of the spacer. The one or more piercing members may each comprise a spike, for example. The further adhesive may be a self-adhesive (pressure-sensitive adhesive for near-instant adhesion), or another settable adhesive configured to cure faster than the settable adhesive. The self-adhesive may have a faster initial grab time than the settable adhesive, e.g., near instantaneous, which is defined as the time taken to support the weight of the spacer and the settable adhesive therein. The spacer may comprise a self-adhesive pad adhered to a body of the spacer, comprising the self-adhesive. The self-adhesive may be covered by a peel-off tab. One face of the self-adhesive pad may be adhered to a body of the spacer and the other opposite face may present the self-adhesive. The self-adhesive pad may comprise a hole aligned with the further opening of the spacer. The securing step of the method may comprise pressing the spacer onto the substantially planar member or substrate, causing the piercing members and / or further adhesive to engage with the substantially planar member or substrate. An advantage is a convenient retaining means for initially holding the spacer in place prior to filling the cavity with the settable adhesive, and after filling the cavity with the settable adhesive while the settable adhesive is curing. The above examples refer to the cavity in the spacer being a through-hole. In an alternative example, the spacer comprises the (first) cavity and a second cavity. The second cavity may have an opening facing the first end. The second cavity may be divided from the first cavity. The second cavity may be fillable or filled by a same or different composition of settable adhesive for securing the spacer to the substantially planar member. This two-cavity design enables a supplier to secure the spacers to the substantially planar member by a settable adhesive, prior to dispatch to a construction site - this may be advantageous in situations where logistical constraints require pre-assembly. In this example, the second cavity would function as the “retaining means”. The piercing members and / or self-adhesive can optionally be omitted. In a further alternative example, the piercing members and / or self-adhesive pad is the sole means by which the spacer is initially secured. For example, the piercing members may be longer, and / or the self-adhesive may utilise a stronger adhesive. In such an implementation, there is no requirement for a cavity opening at the first end of the spacer. The spacer may comprise a vent (or vents) connected to the cavity, into which some of the settable adhesive flows when the settable adhesive is compressed into the cavity as the substantially planar member is pressed against the substrate with the spacer or spacers therebetween. The vent may be a side vent, extending at least part of the way through a side wall of the spacer. The vent may be a hole. The vent may be a through-hole vent, open at one end to the cavity inside the spacer and at its other end to an exterior of the spacer. An advantage of the vent is facilitating substantial abutment of the first and second ends of the spacer with the substantially planar member and the substrate, by reducing or preventing the occurrence of the settable adhesive spreading at the first and / or second end of the spacer, pushing the respective end away from the respective substantially planar member or substrate. This is because the vent provides a space for the compressed settable adhesive to expand into. Therefore, the thickness of the drainage gap between the substantially planar member and the substrate is consistently uniform for each of the spacers. The vent may have a cross-sectional area which is smaller than that of the cavity, but large enough to enable some of the settable adhesive to expand some or all the way through the vent as the substantially planar member is pressed against the substrate. The vent may be an open-sided vent. The open-sided vent may be open at the second end of the spacer, or if the cavity is a through-hole the vent may be open at either the first or second end of the spacer. An advantage of the open-sided vent is allowing some of settable adhesive that flows through the vent to contribute to the adhesion of the spacer to the substrate or substantially planar member. For example, the open-sided vent may be defined as a recess formed in an end face of the spacer. Alternatively, the spacer may comprise legs or feet protruding from an end face of the spacer, the legs or feet being configured to space the end face of the spacer from the respective substantially planar member or substrate, and the vent being defined as the gap between an adjacent pair of the legs or feet. The spacer may comprise a plurality of the vents, each connected to the cavity. The plurality of vents may be formed in different sides of the spacer, including opposing sides. The plurality of vents may comprise at least three or at least four vents at a same end of the spacer. The three, four, or more vents may be generally equally spaced around a circumference of the spacer. An advantage of the symmetrical design is reducing the chance of the spacer being asymmetrically pushed into a cocked / tilted orientation during movement or expansion of the settable adhesive. A first subset of the vents may be open at the first end of the spacer, and a second subset of the vents may be open at the second end of the spacer. An advantage is allowing the portions of settable adhesive that flow into the vents to contribute to the adhesion of the spacer to the substantially planar member, and also to contribute to the adhesion of the spacer to the substrate. If the cavity is a through-hole, the first and second subsets of the vents may be each connected to the cavity. If the spacer comprises the separate first cavity and second cavity as described earlier, the second subset of the vents may be connected to the first cavity and the first subset of the vents may be connected to the second cavity. The first subset of vents may comprise a plurality of vents, and the second subset of vents may comprise a plurality of vents. The first and second subsets of vents may be arranged in an alternating pattern relative to each other. The first subset of the vents may be located at a first set of angular positions around a circumference of the spacer. The second subsets of vents may be located at a second set of angular positions around the circumference of the spacer. The first and second sets of angular positions may be offset from each other. For example, if each subset comprises four vents, the offset may be approximately 45 degrees. If each subset comprises three vents, the offset may be approximately 60 degrees. An advantage of the offset is that the vents at opposite ends are not aligned, avoiding thin bridges of material between the centres of the vents, and therefore allowing a stiff and durable spacer even if the vents are large. For example, the offsetting of the opposite vents enables the vents to have a depth close to, or even greater than 50% of the thickness of the spacer. The spacer may comprise a drip ring located between the first and second ends, extending circumferentially around an outer side surface of the spacer. The drip ring may comprise an indent or a protruding collar, for example. An advantage is that the spacer prevents water from tracking from the substrate to the substantially planar member. The or each spacer may be stackable with another one of said spacers to control a thickness of the drainage gap. According to various, but not necessarily all, embodiments of the invention, there is provided an apparatus comprising a stack of said spacers. If the cavity of each spacer in the stack is a through-cavity, the cavities of the spacers may align to define a single enlarged through-cavity. If the spacer is stackable, and if the spacer comprises one or more protrusions at its first end, the spacer may further comprise one or more sockets at its second end to receive the one or more protrusions of a second said spacer when in a stacked configuration with the second spacer. The protrusions may comprise the piercing members and / or legs and / or feet, as described above. If the spacer is stackable, and if the spacer comprises the further adhesive at its first end, the spacer may be stackable with a second said spacer via the further adhesive. Alternatively, or additionally, the spacer may comprise a thickness adjuster to vary a thickness of the spacer to control a thickness of the drainage gap. The spacer may comprise a pair of parts coupled by the thickness adjuster. One of the parts may define the first end of the spacer, the other part may define the second end of the spacer, and when the parts are coupled by the thickness adjuster the two parts may define a single spacer body with a through-cavity. The thickness adjuster may comprise a threaded coupling. The spacer may be tubular. The spacer may be cylindrical in shape, such as a rounded cylinder. The settable adhesive may comprise a modified silane (MS) adhesive. (“MS Polymer” is a Trademark by Kaneka). The method is suitable for use with many other adhesives, including but not restricted too, cement-based adhesives, fire-resistant types such as silicate adhesives, modified siloxane adhesives, epoxy and polyester adhesives, foam adhesives such as polyurethane and siloxane, bitumen adhesives. According to various, but not necessarily all, embodiments of the invention there is provided a method of providing a drainage gap between a substantially planar member and a substrate, the method comprising: securing a plurality of spacers to the substantially planar member or the substrate via a retaining means, each spacer comprising a first end facing the substantially planar member or substrate to which the spacer is secured, a second end opposite the first end, and an optional cavity having an opening at the second end or at each end; filling the cavity of each spacer or an area between the spacers with a settable adhesive; and pressing the substantially planar member against the substrate to allow the settable adhesive to bond with at least the other of the substantially planar member or substrate. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which: FIG. 1 illustrates an example of a system; FIGS. 2A, 2B illustrate perspective and bottom views of a first spacer; FIG. 3 illustrates a perspective view of a second spacer; FIG. 4 illustrates a perspective view of a third spacer; FIG. 5 illustrates a perspective view of a fourth spacer; FIGS. 6A, 6B, and 6C illustrate perspective, bottom, and side views of a fifth spacer and of a stack of the spacers; FIGS. 7A, 7B, and 7C illustrate perspective, bottom, and side views of a sixth spacer and of a stack of the spacers; FIG. 8 illustrates a side view of a seventh spacer; FIG. 9 illustrates a perspective view of an eighth spacer; FIG. 10 illustrates a side view of a ninth spacer; and FIG. 11 illustrates an example method. DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION FIG. 1 is described with reference to an example implementation. FIG. 1 illustrates a substrate in the form of a structural wall 20, and a substantially planar member 10, in the form of an insulation board for example purposes. The substantially planar member 10 could be another type of board. FIG. 1 further illustrates a system 1 for creating a drainage gap between them. The drainage gap is also referred to as a drainage cavity or ‘Type C’ cavity. The system 1 comprises a set of spacers 100 which are secured firstly to the substantially planar member 10, and then to the structural wall 20. It should be noted that this step could be done in the reverse order. The spacers 100 space the substantially planar member 10 from the structural wall 20, to create the drainage gap. The structural wall 20 can comprise an earth retaining wall, or another type of substrate such as a floor slab. The structural wall 20 may be formed from concrete, masonry, or equivalent structural materials. The structural wall 20 may be planar or non-planar, e.g., piled wall. In other examples, the substrate can comprise a frame or other construction secured to a structural wall or floor slab. In examples where the substantially planar member 10 is an insulation board, the board may comprise polystyrene, XPS, phenolic foam, urethane foam, aerogel, cement-bound polystyrene, wood composite, or other insulating materials suitable for application in the system described. The precise materials and finish of the substantially planar member 10 depend on how the spacers 100 are secured to the substantially planar member 10. In other examples, a different substantially planar member is used such as plasterboard, waterproofed plasterboard, thin beams rather than boards, etc. In some, but not necessarily all examples, the system 1 as supplied may comprise the spacers 100 and also a set of substantially planar members 10. FIG. 1 illustrates the spacers 100 arranged in an array that covers the majority of the area of a face 12 of the substantially planar member 10. The spacers 100 are positioned such that that a minimum of constant drainage gap occurs over the whole area of the substantially planar member 10. As will be described, a settable adhesive is injected into cavities of the spacers 100, and then the substantially planar member 10 with the spacers 100 is lifted against the structural wall 20 and pressed against the structural wall 20. The settable adhesive cures and holds the substantially planar member 10 against to the structural wall 20, with a constant drainage gap therebetween. It should be noted that the process could be done in different order with the spacers first applied to wall. FIGS. 2A-10 illustrate example implementations of the spacers 100 configured for use in the system 1 of FIG. 1. FIGS. 2A-2B illustrate a spacer 100A having a first design. The spacer 100A has a first end 102 which faces the substantially planar member 10 in-use, and an opposite second end 104 which faces the structural wall 20 in-use. The separation of the first and second ends 102, 104 defines the thickness of the spacer 100A, which defines the thickness of the drainage gap- In an example, the spacer 100A has a nominal thickness of 20 mm, or another thickness from the range 2mm to 75mm. The minimum thickness is large enough to allow passage of a typical-sized water droplet. An advantageous thickness range is from 2mm to 25mm in the context of cavity drains, because this provides an adequate gap for water drainage without substantially compromising on an interior space of the building. The thickness could be greater for other applications. In use, the thickness may be substantially equal to the distance between the substantially planar member 10 and the structural wall 20 at the location of the spacer 100A. This nominal thickness is therefore substantially equal to the minimum or prescribed thickness of the drainage gap. The precise nominal thickness depends on any requirements set out by building standards and the required drainage capacity of the cavity. The spacer 100A comprises a body 108 in the shape of a circular cylinder, or another tubular form. The spacer could also be in polygonal form such as a triangular, square or hexagonal. The body 108 of the spacer 100A has a first end face 110 shown in the top perspective view of FIG. 2A, an opposite second end face 112 shown in the bottom view of FIG. 2B, and a tubular side wall 114 connecting the first and second end faces 110, 112, which defines an outer side surface 116 of the spacer 100A. In-use, the first end face 110 of the body 108 generally abuts against the substantially planar member 10, and the second end face 112 of the body 108 generally abuts against the structural wall 20. Therefore, the first and second end faces 110, 112 of the body 108 define the first and second ends 102, 104 of the spacer 100A. The dimensions of the spacer 100A referred to above may be the dimensions of the body 108. The spacer 100A further comprises a cavity 118 for receiving the settable adhesive. The cavity 118 is in the form of a through-hole, extending in the thickness direction between first and second openings 120, 122 of the cavity 118. The first opening 120 is at the first end 102 of the spacer 100A, and the second opening 122 is at the second end 104 of the spacer 100A. The illustrated cavity 118 is a central / middle cavity, surrounded by the side wall 114 of the body 108. The cavity 118 may have generally the same cross-section shape as the side wall 114, in this example circular. The cavity 118 enables the same application / dot of settable adhesive to fill the cavity 118 and bond with both the substantially planar member 10 and the structural wall 20. This enables the spacer 100A to provide the function of securing the substantially planar member 10 to the structural wall 20, in addition to providing a drainage gap. In the illustrated example, the first opening 120 of the cavity 118 is located at the first end face 110 of the body 108 of the spacer 100A, and the opposite second opening 122 of the cavity 118 is located at the second end face 112 of the body 108 of the spacer 100A shown in the bottom view of FIG. 2B. The first opening 120 of the cavity 118 of the spacer 100A is co-planar with or recessed relative to the perimeter of the first end face 110 of the body 108 of the spacer 100A, and the opposite second opening 122 of the cavity 118 is coplanar with or recessed relative to the perimeter of the opposite second end face 112 of the body 108 of the spacer 100A. In use, the cavity 118 is overfilled with the settable adhesive, for example via an adhesive gun. Sufficient settable adhesive is injected into the cavity 118 that one portion of the settable adhesive is in contact with the substantially planar member 10 at the first opening 120 at the first end face 110 of the body 108 of the spacer 100A, and another portion of the settable adhesive protrudes from the second opening 122 at the second end face 112 of the body 108 of the spacer 100A. Therefore, when the second end face 112 of the body 108 of the spacer 100A is pressed against the structural wall 20, the settable adhesive will be compressed into the smaller volume of the cavity 118. The protruding portion of settable adhesive may have a tendency to spread slightly between the second end face 112 of the body 108 and the structural wall 20. This may affect the planarity of the spacer 100A and therefore the accuracy of the drainage gap. To mitigate this effect, the spacer 100A further comprises a pair of vents 124 connected to the cavity 118, into which the compressed settable adhesive can expand. The vents 124 are formed as rounded, e.g., semi-circular, recesses, recessed into the second end face 112 of the body 108. Each recess therefore extends into the side wall 114 of the body 108. The vents 124 provide a space for the compressed settable adhesive to expand into. This reduces the amount of settable adhesive that spreads between the second end face 112 of the body 108 and the structural wall 20. The vents 124 are through-vents open to the cavity 118 and to the outer side surface 116. Therefore, some of the settable adhesive may protrude out of the vents 124, depending on the thixotropy of the settable adhesive. However, the thixotropy of the settable adhesive and the vent sizes could advantageously be selected so that the settable adhesive does not pour out of the vents 124 in a manner that empties the cavity 118 of settable adhesive. The illustrated vents 124 could alternatively be blind vents that are open to the cavity 118 but blocked by the outer side surface 116 of the side wall 114. The settable adhesive inside each vent 124 is able to bond directly to the structural wall 20 because each vent 124 is recessed into the second end face 112 of the body 108, and is therefore in contact with the structural wall 20. The illustrated vents 124 each have a cross-sectional area which is smaller than that of the cavity 118, but large enough to enable some, not all, of the settable adhesive to flow most or all the way through the vent 124 as the substantially planar member 10 is pressed against the structural wall 20, abutting the first and second end faces 110, 112 of the spacer 100A therebetween. The two vents 124 illustrated in FIGS. 2A-2B are located to opposite sides of the second end face 112 of the body 108 of the spacer 100A. A symmetrical design reduces the likelihood that the spacer 100A will become cocked / tilted in use. However, it is possible that a spacer 100A with only one vent 124 connected to the cavity 118 may offer acceptable performance. The precise shape, size, and number of vents 124 depends on the thixotropy of the settable adhesive, among other things. The illustrated vents 124 are open vents recessed into the second end face 112 of the spacer 100A, to provide a stronger bond to the structural wall 20 due to the added contribution of the settable adhesive inside the vents 124. It would be appreciated that the vents 124 could be relocated to the first end face 110 of the spacer 100A to provide a stronger bond to the substantially planar member 10. Alternatively, vents 124 could be provided at both the first and second end faces 110, 112 of the spacer 100A, to reinforce both ends. The choice depends on which end(s) of the spacer 100A would benefit from a stronger bond. When the spacer 100A is first attached to the substantially planar member 10 and the settable adhesive is poured into its cavity 118, the settable adhesive has not yet cured so is unable to robustly support the spacer 100A. If not for a separate retaining means 140 described below, the spacer 100A could slide or fall off the substantially planar member 10 when the substantially planar member 10 is lifted to an upright position. The retaining means 140 illustrated in FIG. 1 takes the form of four piercing members 142, which penetrate the substantially planar member 10 to temporarily fix the spacer 100A to the substantially planar member 10. Until the settable adhesive has cured, the piercing members 142 are the primary means by which the spacer 100A is secured to the substantially planar member 10. The piercing members 142 embedded in the substantially planar member 10 allow the substantially planar member 10 to be lifted to an upright orientation, without the spacer 100A falling off. The piercing members 142 are mounted to the first end face 110 of the body 108. Each piercing member 142 comprises a spike for penetrating into the substantially planar member 10. Each spike is configured, via its sharpness and material choice, to penetrate an substantially planar member 10 of typical penetrability, such as an expanded polystyrene substantially planar member 10, due to hand-applied pressure pushing the spacer 100A against the face 12 of the substantially planar member 10. Alternatively, a hammer, mallet or other mechanical means may be used. Each illustrated spike is tapered to a point. In other examples, the spikes are non-tapered but sufficiently slender to penetrate the substantially planar member 10. The piercing members 142 may be formed from the same material as the body 108 of the spacer 100A. The piercing members 142 and the body 108 may be a single integrally-formed part. If the spacers 100 are instead initially secured to the structural wall 20 such as a masonry wall, the piercing members 142 may be formed from a harder material than the structural wall 20, such as steel. In the above example, the piercing members 142 are pre-mounted to the supplied spacer 100A. In other examples, the supplied spacer 100A just comprises holes and / or head seats into which the installer can insert their own separate piercing members 142 such as nails or screws. The lengths of the piercing members 142 are selected so that the piercing members 142 do not penetrate the entire thickness of the substantially planar member 10. For example, the lengths of the piercing members 142 may be less than 50 mm, which is less than the thickness of a typical substantially planar member 10. To provide a sufficient hold, the lengths of the piercing members 142 may be at least 0.5 mm. An advantageous sub-range is at least 1mm and / or no greater than 20mm, which is long enough to attach to the underlying surface, while minimising penetration through the surface. A length shorter than 1mm could fail to account for any unevenness in the surface. A length that is too long may not be compatible with some thin boards. The number of piercing members 142 may vary. One or more piercing members 142 could be provided. If the piercing members 142 are short, more may be provided. The body 108 of the spacer 100A is formed from a single moulded part. The body 108 of the spacer 100A can be formed from a material such as plastic, metal, or ceramic. Typically plastic which can be easily moulded can be used such as polyolefin types and polystyrene. A ceramic or steel material, or a combination thereof, could be used for fire-resistant versions. If a thicker drainage gap is required, a pair of the spacers 100A may be configured to be stacked on each other to enable a drainage gap twice as thick, or to form even higher stacks. Each spacer 100A is provided with sockets 160 formed in the second end face 112 of the body 108 of the spacer 100A. The piercing members 142 of the lower spacer 100A in a stack are locatable into the sockets 160 of the upper spacer 100A in a stack, to secure the spacers 100A in a stacked configuration. Alternatively, the piercing members 142 may pierce the body 108 of the other space 100A in the stack, if the piercing members 142 are formed from a harder material than the body 108. FIG. 3 illustrates a spacer 100B having a second design. The spacer 100B has the required features and any one or more of the optional features of the spacer 100A of FIGS. 2A-2B, except where stated and shown otherwise. Instead of piercing members 142, the retaining means 140 uses further adhesive to create the temporary fix to the substantially planar member 10. The illustrated spacer 100B comprises a double-sided self-adhesive pad 144 stuck to the first end face 110 of the spacer 100B, the exposed face of which presents self-adhesive for sticking the spacer 100B to the face of the substantially planar member 10 or to the substrate when the spacer 100B is pressed against the substantially planar member 10 or substrate. The pad comprises a central hole aligned with the first opening 120 of the cavity 118, to allow the main settable adhesive to reach the relevant underlying surface. The exposed face of the pad can be covered with a peel-off tab, for example. Alternatively, the further adhesive can be a further settable adhesive that is applied to the first end face 110 of the body 108 of the spacer 100B on-site. The further settable adhesive is chosen to be faster-curing than the settable adhesive in the cavity 118. The further adhesive may have good initial grab to aid positioning. The settable adhesive may provide long term adhesive performance. Spacers 100B of FIG. 3 may be stacked by adhering the second end face 112 of the overlying spacer 100B onto the further adhesive of the underlying spacer 100B in the stack. FIG. 4 illustrates a spacer 100C having a third design. The spacer 100C has the required features and any one or more of the optional features of the spacer 100B of FIG. 3, except where stated and shown otherwise. In summary, the spacer 100C of FIG. 4 has additional vents 124 at the face where the vents 124 are provided. The spacer 100C comprises four vents 124, equi-spaced from each other by approximately 360 / n degrees around the circumference of the spacer 100C, where n is the number of vents 124 (three or more). In the illustrated example, the four vents 124 are spaced apart from each other by 90 degrees. FIG. 5 illustrates a spacer 100D having a fourth design. The spacer 100D has the required features and any one or more of the optional features of the spacer 100A of FIGS. 2A-2B, except where stated and shown otherwise. In summary, the spacer 100D of FIG. 5 has additional vents 124 at the face where the vents 124 are provided. The spacer 100D comprises four vents 124, equi-spaced from each other by approximately 360 / n degrees (90 degrees in this example). FIGS. 6A-6C illustrate a spacer 100E having a fifth design. The spacer 100E has the required features and any one or more of the optional features of the spacer 100D of FIG. 5, except where stated and shown otherwise. As mentioned earlier, vents 124 could be provided at both ends of the spacer 100E to provide additional strength. FIGS. 6A-6C illustrate eight vents 124, where a first subset comprising four vents 124A are open at the first end face 110 of the body 108 of the spacer 10OE, and a second subset comprising four 22 vents 124B are open at the second end 104 of the body 108 of the spacer 10OE. The number of vents 124 in total, or in each subset, may vary. The first and second subsets of vents 124A, 124B are arranged in an alternating pattern around the circumference of the spacer 100E. The vents within each subset of vents 124A, 124B are spaced apart from each other by 360 / n degrees (90 degrees in the example), but the two subsets are offset from each other by 360 / 2n degrees (45 degrees in the example) so that adjacent vents 124A, 124B belong to alternating subsets and are open at opposite end faces 110, 112 of the spacer 100E. The offsetting of the subsets of vents 124A, 124B allows each vent to be larger, having a depth of approximately 50% of the thickness of the spacer 100E without the body 108 being too thin adjacent to the apexes of the vents. As shown in FIG. 6C, each spacer 100E may be stackable with another one of itself. The manner of stacking may be as described in relation to FIGS. 2A-2B. When stacked, a vent 124A in the first end face 110 of the upper spacer 100E in the stack 101 is aligned or mostly aligned with a vent 124B in the second end face 112 of the lower spacer 100E in the stack 101, to form an enlarged combined vent, which in this non-limiting example is a circle defined by the alignment of the two semi-circular vents 124A, 124B. This usefully provides the stack 101 with a range of vent sizes, so that if the settable adhesive is more thixotropic than expected then it will still be able to flow through one or more of the vents 124. Another manner of providing a plurality of vent sizes would be for the vents 124 of a single spacer 100E to have different sizes than each other (not shown). FIGS. 7A-7C illustrate a spacer 100F having a sixth design. The spacer 100F has the required features and any one or more of the optional features of the spacer 100A of FIGS. 2A-2B, except where stated and shown otherwise. The spacer 100F comprises a plurality of legs 130, in the form of blunt rods, mounted to each of the first and second end faces 110, 112 of the body 108 of the spacer 100F. The legs 130 act as spacers themselves, to space the first and second end faces 110, 112 of the body 108 of the spacer 10OF apart from the substantially planar member 10 and the structural wall 20. The tips of the legs 130 abut against the substantially planar member 10 and the structural wall 20. The legs 130 are blunt meaning they perform an end-abutting function rather than a piercing function. The tips of the legs 130 collectively define a flat plane at each end of the spacer 100F to abut against the substantially planar member 10 and the structural wall 20. The legs 130 are an alternative means of defining the vents 124, instead of the vents 124 being recessed into the end faces 110, 112. The gaps between adjacent legs 130 can be described as vents 124. Alternatively, or additionally, the flexibility of the legs 130 themselves provides the function of a vent, because the legs 130 may be flexed radially outwardly by the spreading of the compressed settable adhesive, creating additional internal volume for the settable adhesive to spread into. FIGS. 7A-7C illustrate a large quantity of the legs 130, e.g., more than six, more than twelve, or several dozen legs 130, or more. The use of many legs 130 provides a high surface area for the settable adhesive to bond to, and the high density of legs 130 results in small gaps therebetween, preventing the settable adhesive from escaping from the spacer 100F through the gaps between the legs 130. The illustrated legs 130 are arranged in an array, the array defining a plurality of rows of legs 130, each row being mounted to the respective first or second end face 110, 112 of the body 108 at a different diameter from the centre of the spacer 100F, and each row comprising a plurality of legs 130. The use of multiple rows further helps to prevent escape of the settable adhesive. The piercing members 142 illustrated in FIGS. 7A-7C are mounted to the first end face 110 of the body 108 along with the legs 130. The piercing members 142 are longer than the legs 130 so that the piercing members 142 can still penetrate the substantially planar member 10. In other examples, the piercing members 142 are replaced with adhesive-tipped bosses. As shown in FIG. 7C, each spacer 100F may be stackable with another one of itself. The manner of stacking may be as described in relation to FIGS. 2A-2B. Further, the legs 130 mounted to the first end face 110 of the lower spacer 10OF in the stack 101 may interdigitate with the legs 130 mounted to the second end face 112 of the upper spacer 100F in the stack 101. Together, the interdigitated legs 130 define a barrier preventing any unwanted escape of the settable adhesive where the spacers 100F join. FIG. 8 illustrates a spacer 100G having a seventh design illustrating a variant of FIGS. 7A-7C. In FIG. 8, the longer legs 130 are replaced with shorter feet 180, which are less numerous. The feet 180 are shown mounted to one face 112 rather than to both faces 110, 112, although this depends on implementation. The vents 124 are defined as the circumferential gaps between the feet 180 of FIG. 8. The use of feet 180 results in thinner vents 124. The thinner vents 124 of the spacer 100G of FIG. 8 are suitable for less-thixotropic settable adhesives that flow easily. Any of the embodiments can comprise feet 180 or legs 130. FIG. 9 illustrates a spacer 100H having an eighth design. The spacer 100H has the required features and any one or more of the optional features of the spacer 100D of FIG. 5, except where stated and shown otherwise. Firstly, the vents 124 are formed in the first end face 110 of the spacer 100H, rather than the second end face 112. In other examples, the vents 124 may be located at the other end. Secondly, the spacer 100H further comprises an indented drip ring 150 located in the side wall 114 of the body 108 of the spacer 10OH, between the first and second end faces 110, 112 of the body 108. The drip ring 150 prevents water from tracking from the structural wall 20 to the substantially planar member 10. The drip ring 150 extends circumferentially around an outer side surface 116 of the side wall 114. Although the illustrated drip ring 150 is indented into the side wall 114, in other examples the drip ring 150 may be a protruding collar. Any of the embodiments can comprise a drip ring 150. Although piercing members 142 are shown, adhesive may be provided in other examples to function as the retaining means 140. FIG. 10 illustrates a spacer 1001 having a ninth design. The body 108 of the spacer 1001 is formed from first and second parts 172, 174, coupled together by a thickness adjuster 170 in the form of a threaded coupling. The thickness adjuster 170 allows the separation of the first and second parts 172, 174 to be modified, to control the thickness of the drainage gap. The first part 172 comprises the retaining means 140 and mounts to the substantially planar member 10 or structural wall 20. The second part 174 comprises a cavity such as a through-hole, for mounting to the other one of the structural wall 20 or substantially planar member 10. The first part 172 may further comprise a cavity such as a through-hole. When the first and second parts 172, 174 are coupled, the cavities may align to form a combined cavity 118 extending through both parts 172, 174. One or both of the parts comprises vents 124. One of the parts comprises a male threaded portion of the thickness adjuster 170, and the other part comprises a female threaded portion of the thickness adjuster 170. Any of the embodiments can comprise a thickness adjuster 170. FIG. 11 is a flowchart illustrating an example assembly method 200 of providing a drainage gap between the substantially planar member 10 and the structural wall 20. At block 202, the method 200 comprises securing a plurality of the spacers 100 to a face 12 of the substantially planar member 10 or to the substrate (e.g., structural wall 20) via the retaining means 140, the first end 102 of each spacer facing the substantially planar member or substrate. For example, where the retaining means 140 comprises piercing members 142, this can comprise pressing (by-hand) or hammering the spacers 100 into the face 12 of the substantially planar member 10 or into a face of structural wall 20. If the retaining means 140 comprises adhesive, this can comprise pressing (by-hand) the spacers 100 onto the face 12 of the substantially planar member 10 or into a face of the structural wall 20. At block 204, the method 200 comprises filling the cavity 118 of each spacer with a settable adhesive, the cavity 118 being overfilled to cause a portion of the settable adhesive to protrude from the spacers 100 at the second ends. For example, the settable adhesive can comprise a modified silane (MS) cream-based adhesive. Such adhesives will self-cure via hydrolysis and condensation. The settable adhesive may be applied using an adhesive gun. Other example adhesives include cement-based adhesives, fire-resistant types such as silicate adhesives, modified siloxane adhesives, epoxy and polyester adhesives, foam adhesives such as polyurethane and siloxane, bitumen adhesives. A modified siloxane and / or modified silane adhesive advantageously has high strength for structural applications, has a fast grab time allowing installers to work rapidly, and is moisture-curing meaning that it reacts with humidity in the air to cure over time. For fire-resistant applications, a cement-based or silicate adhesive could be used, or any polymer adhesive with fire-retardant additives. At block 206, the method 200 comprises pressing the substantially planar member against the substrate to allow the settable adhesive in the spacers 100 to bond with at least the substrate. This will compress the protruding settable adhesive, causing some of the settable adhesive within the cavity 118 to expand into the vents 124. The pressing operation may be maintained until the settable adhesive has sufficiently cured to hold the substantially planar member 10. Advantageously, the substantially planar member 10 may be held by only the spacers 100 via the settable adhesive without further mechanical fixings. However, mechanical fixings could provide supplementary support. Block 206 may be performed a short time after block 204, while the settable adhesive in each spacer is still in an uncured liquid state. This enables the settable adhesive in the cavity 118 of each spacer to further bond to the structural wall 20. Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. In some implementations, no vents 124 may be needed. The above examples refer to the cavity 118 in the spacer being a through-hole. In an alternative example, the spacer comprises two divided cavities. One cavity is open at the first end 102 of the spacer, and the other cavity 118 is open at the second end. This may be useful if the spacers 100 are pre-attached to the substantially planar member 10, in the factory. Settable adhesive may be applied to cavity open at the first end 102 in the factory, to act as the (permanent) retaining means 140 attaching the spacers 100 to the substantially planar member 10. Settable adhesive may later be applied to the other cavities 118 on-site, for securing the spacers 100 to the structural wall 20. In a further alternative example, a settable adhesive is not used to secure the spacer to the substantially planar member. Therefore, there is no cavity opening in the first end 102 of the spacer. Instead, the piercing members 142 and / or the further adhesive described earlier are used for a permanent connection. For example, the piercing members 142 may be longer, and / or the self-adhesive may utilise a stronger adhesive. In a further alternative example, the settable adhesive fills an area between the spacers. In such an example, the spacers may not require cavities at all. In some alternative examples, the retaining means is located near but not at the first end of the spacer. Features described in the preceding description may be used in combinations other than the combinations explicitly described. For example, any of the designs of spacer can have either type of retaining means 140. Any of the spacers 100 may have a drip ring 150. Any of the spacers 100 may comprise a thickness adjuster 170. Any of the spacers 100 may have any of the types of vent described herein. 5 Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, 10 those features may also be present in other embodiments whether described or not. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be 15 understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A method of providing a drainage gap between a substantially planar member and a substrate, the method comprising:securing a plurality of spacers to the substantially planar member or the substrate via a retaining means, each spacer comprising a first end facing the substantially planar member or substrate to which the spacer is secured, a second end opposite the first end, and a cavity having an opening at the second end or at each end;filling the cavity of each spacer with a settable adhesive, the cavity being overfilled to cause a portion of the settable adhesive to protrude from the spacer at the second end; andpressing the substantially planar member against the substrate to allow the settable adhesive to bond with at least the other of the substantially planar member or substrate.

2. The method of claim 1, wherein the spacer has a nominal thickness from the range 2mm to 25mm.

3. The method of claim 1 or 2, wherein the step of pressing the substantially planar member against the substrate is performed while the settable adhesive in each spacer is still in an uncured liquid state, enabling the settable adhesive to further bond to the substrate.

4. The method of claim 1,2, or 3, wherein the settable adhesive comprises a modified silane adhesive..

5. The method of any preceding claim, wherein the spacer is a cavity drain spacer, wherein the substantially planar member is a slab or panel, and wherein the substrate is a wall or floor slab or a frame secured thereto.

6. The method of any preceding claim, wherein the cavity of the spacer comprises the opening at the second end and also a further opening at the first end of the spacer, the cavity being a through-hole between the first and second ends of the spacer enabling the settable adhesive to bond with both the substantially planar member and the substrate.

7. The method of any preceding claim, wherein the retaining means is located at or near the first end of the spacer.

8. The method of any preceding claim, wherein the retaining means comprises one or more piercing members and / or a further adhesive, to secure the spacer to the substantially planar member or the substrate.

9. The method of any preceding claim, wherein the spacer comprises a vent connected to the cavity, into which some of the settable adhesive flows when the settable adhesive is compressed into the cavity as the substantially planar member is pressed against the substrate with the spacer or spacers therebetween.

10. The method of claim 9, wherein the vent is a side vent, extending at least part of the way through a side wall of the spacer.

11. The method of claim 9 or 10, wherein the vent is a through-hole vent, open at one end to the cavity inside the spacer and at its other end to an exterior of the spacer.

12. The method of claim 9, 10, or 11, wherein the vent has a cross-sectional area which is smaller than that of the cavity, but large enough to enable some of the settable adhesive to expand some or all the way through the vent as the substantially planar member is pressed against the substrate.

13. The method of any one of claims 9 to 12, wherein the vent is an opensided vent, wherein the open-sided vent is open at the second end of the spacer, or wherein the cavity is a through-hole and the vent is open at either the first or second end of the spacer.

14. The method of any one of claims 9 to 13, wherein the spacer comprises a plurality of the vents, each connected to the cavity.

15. The method of claim 14, wherein the plurality of vents are formed in different sides of the spacer, including opposing sides.

16. The method of claim 15, wherein a first subset of the vents is open at the first end of the spacer, and a second subset of the vents is open at the second end of the spacer.

17. The method of claim 16, wherein the cavity is a through-hole, and wherein the first and second subsets of the vents are each connected to the cavity.

18. The method of claim 16 or 17, wherein the first subset of vents comprises a plurality of vents, and the second subset of vents comprises a plurality of vents, and wherein the first and second subsets of vents are arranged in an alternating pattern relative to each other.

19. The method of claim 18, wherein the first subset of the vents is located at a first set of angular positions around a circumference of the spacer, wherein the second subset of vents is located at a second set of angular positions around the circumference of the spacer, and wherein the first and second sets of angular positions are offset from each other.

20. The method of any preceding claim, wherein the spacer comprises a drip ring located between the first and second ends, extending circumferentially around an outer side surface of the spacer.

21. The method of any preceding claim, comprising stacks of the spacers, to control a thickness of the drainage gap.

22. The method of claim 21, wherein the cavity of each spacer in the stack is a through-cavity, and wherein the cavities of the spacers align to define a single enlarged through-cavity.

23. A cavity drain spacer, dimensioned to provide a drainage gap between a substantially planar member and a substrate, the spacer comprising a first end, a second end, a retaining means for securing the spacer to the substantially planar member or the substrate with the first end facing the substantially planar member or substrate, and the spacer further comprising a cavity having at least an opening at the second end or at each end and which is fillable by a settable adhesive for securing the spacer to at least the other of the substantially planar member or the substrate.

24. A system comprising a plurality of the cavity drain spacers as claimed in claim 23, wherein the system further comprises the substantially planar member, and wherein the spacers are secured or securable to the substantially planar member or the substrate by the retaining means.

25. A method of providing a drainage gap between a substantially planar member and a substrate, the method comprising:securing a plurality of spacers to the substantially planar member or the substrate via a retaining means, each spacer comprising a first end facing the substantially planar member or substrate to which the spacer is secured, a second end opposite the first end, and an optional cavity having an opening at the second end or at each end;filling the cavity of each spacer or an area between the spacers with a settable adhesive; andpressing the substantially planar member against the substrate to allow the settable adhesive to bond with at least the other of the substantially planar 5 member or substrate.

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