[ 001 ] The present invention relates to screed rails , and in particular an extender for a screed rail and a modular screed rail system .

[ 002 ] Screed rails are used to define the perimeter of a volume in which a settable material is to form a slab . Such slabs are typically made of concrete to form for example a floor within a building, and are cast in situ . The screed rail also determines the surface level of the slab, and may be used to connect adj acent slabs , for example with dowels or tie bars passing through apertures in the screed rail . The upper surface of the screed rail is normally flat to allow for levelling of the cast slabs . The screed rail should be suf ficiently robust to withstand the weight of heavy screeding and vibrating beam machines and also provide smooth passage for these machines , as they travel along the uppermost surface .

[ 003 ] Thermal expansion and contraction of the cured cast slab may exert considerable forces on the screed rail . For example , i f a timber screed rail is used it should be removed before a second slab is cast , which can delay the installation by several days . I f a steel , concrete or hard plastics screed rail is used and left in the floor, when the slabs shrink, for example in cold weather, a gap may form at the side of the screed rail , allowing ingress of detritus , and of fering no support to the arrisses of the slabs , permitting spalling and damage to occur . I f a hollow plastics extruded screed rail is used, when the gap closes in warm weather the screed rail may be crushed, rendering it unserviceable when the gap opens at lower temperatures .

[ 004 ] Accordingly, screed rails have been developed to accommodate slab expansion and contraction . For example , GB 2575777 discloses a screed rail comprising a resiliently compressible upwardly extending portion having side faces which are connected by and movable relative to each other through resiliently deformable bridges . Under compression, lateral forces applied to the side faces deform the bridges , thus pushing the side faces towards each other, and under reduced lateral pressure the bridges push the side faces away from each other, back towards their original positions .

[ 005 ] EP 1365150 discloses " shuttering formwork" comprising an elongate body member comprising a base portion having an upper face , and a upwardly extending compression portion having first and second side faces , the base portion upper face and the first and second compression portion side faces each being a resiliently deformable surface .

[ 006 ] It is to be noted that a number of terms are used to describe screed rails , including " formwork" and " shuttering" . In the present speci fication the term " screed rail" is used, and encompasses any rail , formwork or shuttering which is used to define a physical boundary for casting a settable material , such as concrete .

[ 007 ] The present invention seeks to provide improvements for screed rails .

[ 008 ] Thus , according to a first aspect of the present invention there is provided an extender for extending the height of a screed rail , the extender comprising : an elongate body having side portions defining a lower end portion and an upper end portion; wherein the side portions are connected by at least one resiliently deformable bridge therebetween, the bridge permitting lateral movement of the side portions towards and away from each other ; wherein the lower end portion and the upper end portion are configured to be engageable with the upper end portion and lower end portion respectively of a second extender, such that a plurality of extenders may be connected together .

[ 009 ] In use , the height of a screed rail determines the height ( depth) of the settable material , i . e . the surface level of the set slab . The extender of the first aspect of the present invention may be used to extend the height of a screed rail which is suitably configured to attach to the lower end portion of the extender, for providing thicker slabs . One or more extenders may be used according to the height requirements for the screed rail . Thus , the height of a screed rail may be increased by connecting a first extender to the screed rail through attachment of the lower end portion of the extender to the screed rail . The height of the screed rail may be further increased by connecting a second extender to the first extender by engaging the lower end portion of the second extender to the upper end portion of the first extender, and further extenders may be connected in this way until the desired screed rail height is reached . The extender of the present invention thus allows for the provision of screed rails of di f ferent heights by extending the height of a screed rail through the addition of one or more extenders , obviating the need for separate screed rails of di f ferent heights , with consequent economic and material benefits .

[ 0010 ] The extender of the first aspect of the present invention comprises an elongate body, i . e . the extender has a substantially greater length dimension compared to its height and width, so as to correspond to the relative dimensions of a screed rail to which it is intended to connect . The body has side portions which are connected by at least one resi liently deformable bridge therebetween . The side portions are thus relatively movable towards and away from each other, for example when external lateral forces are applied and released, such as during expansion and contraction of a set slab of material , such as concrete . When external forces press against the side portions the connecting bridge deforms under the pressure , moving the side portions relatively closer to each other, and when the pressure is released, the resilience of the connecting bridge pushes the side portions apart . The connecting bridge preferably deforms in preference to the side portions , which preferably do not deform under the external pressures typically encountered during use . Accordingly, the connecting bridge is preferably either formed from a material which is more easily deformed under pressure compared to the material from which the side portions are formed, or i f made from the same material as the side portions , for example in the case where the extender is formed as a single integral piece , the connecting bridge preferably has dimensions which are configured so that it will preferentially deform over the side portions . For example , the connecting bridge may be thinner than the side portions .

[ 0011 ] The extender may comprise one or more bridges , according to the intended use of the extender and the forces to which the side portions are expected to be subj ected during use . For example , the extender may comprise one , two , three or more connecting bridges . The bridges may conveniently have a curved cross-section ( e . g . an arc of a circle , such as an approximate C-shape or semicircle ) .

[ 0012 ] The side portions define a lower end portion and an upper end portion of the extender body . The lower end portion and/or the upper end portion preferably comprise a recess , forming an elongate channel along some or all the length of the body . The upper end portion recess may be defined by the upper ends of the side portions optionally with the uppermost connecting bridge . The upper end portion recess may for example be used to receive a filler material , or for example an elongate resiliently compressible member to provide additional resilience to lateral compressive forces . The upper end portion recess may in use receive the lower end portion of another extender, to connect two extenders together . Thus , the lower end portion recess is preferably configured to receive the upper end portion of another extender, more preferably to intimately receive the upper end portion of another extender and hold it in pos ition . For example , the lower end portion may comprise internal flanges forming recesses or pockets configured to receive the upper ends of the side portions . Alternatively, the lower end portion may comprise a downwardly extending member, for example formed as part of a connecting bridge , which is configured to fit into the upper end portion recess .

[ 0013 ] The extender preferably comprises locking means for locking lower and upper end portions together . For example , one of the upper and lower end portions may comprise one or more proj ections , and the other of the upper and lower end portions may comprise one or more corresponding receivers to receive the proj ections . For example , the lower end portion may comprise a receiver channel in at least one of its inner surfaces to receive a corresponding proj ection positioned on at least one corresponding outer surface of the upper end portion . The lower end portion locking means also preferably enables the extender to lock onto a screed rail .

[ 0014 ] The upper end portion is preferably configured to releasably engage with a cover strip . The cover strip preferably extends partly or fully along the length of the extender and may be releasably positioned over the upper end portion of the extender to prevent ingress of material during use . Preferably, the cover strip can be removed, for example when the material has set . The cover strip may comprise a downwardly extending member which is configured to fit into the upper end portion recess of the extender, and/or may comprise locking means as described above .

[ 0015 ] The lower end portion is preferably configured to engage with a screed rail . Screed rails typically have a base portion, which in use rests on the foundation layer to support the rail , and a portion which extends upwardly from the base portion to define an edge of the volume containing the settable material . The lower end portion of the extender is preferably configured to engage with the upper end of the upwardly extending portion of the screed rail , to thus extend the height of the screed rail to allow for a greater depth of settable material . Thus , the screed rail may comprise an upper recess into which a downwardly proj ecting member of the lower portion of an extender is configured to fit .

[ 0016 ] Additional resil ience to lateral compressive forces may be achieved through one or more elongate resiliently compressible members positioned within the extender body, for example positioned in one or more channels formed by a connecting bridge and/or the upper end recess and/or lower end recess . The elongate resiliently compressible member may be formed, for example , from a resiliently compressible rubber or sponge ( e . g . Neoprene ) .

[ 0017 ] The extender is preferably formed from a plastics material . The extruder may be formed as a single integral piece , for example as a single plastics extrusion, and may be cut to a desired length on site . For example , the plastics material may be formed from UPVC (unplastici zed polyvinyl chloride ) . [ 0018 ] The extender should have dimensions which are appropriate for its use in extending the height of a screed rail , and for use with a screed rail cover strip . Screed rail dimensions vary, and are typically in the region of 2000- 3000mm length, 50- 150mm in width (base portion) , and 50- 150mm height . The extender may have a height of for example 25- 50mm .

[ 0019 ] According to the present invention in a second aspect there is provided a modular screed rail system, comprising at least one extender in accordance with the first aspect of the present invention, a screed rail , and optionally a cover strip ; wherein the screed rail comprises an elongate body comprising a base portion and an upwardly extending portion, and the lower end portion of the extender is configured to be engageable with the upwardly extending portion of the screed rail , and the upper end portion of the extender is releasably engageable with the cover strip, i f present .

[ 0020 ] The modular screed rail system of the second aspect of the present invention thus provides for the height of the screed rail to be increased by connecting a first extender to the screed rail through attachment of the lower end portion of the extender to the screed rail . The height of the screed rail may be further increased by connecting a second extender to the first extender by engaging the lower end portion of the second extender to the upper end portion of the first extender, and further extenders may be connected in this way until the desired screed rail height is reached . In this way the height of the screed rail may be set as required, obviating the need for separate screed rails of di f ferent heights , with consequent economic and material benefits .

[ 0021 ] The screed rail used in the system of the present invention comprises an elongate body, i.e. the screed rail has a substantially greater length dimension compared to its height and width. The body preferably has a base portion and an upwardly extending portion.

[0022] The base portion of the screed rail is the portion which in use rests upon the foundation layer, i.e. the layer upon which the slab of settable material is to be formed. The base portion may have fixing means for fixing the base portion to the foundation layer, such as apertures through which fixing pins or adhesive material (e.g. mortar material) may be placed, or a contoured surface, e.g. serrated surface, for fixing to the foundation layer with adhesive material (e.g. mortar material) . The base portion may comprise a hollow structure, to reduce weight and use of materials, with internal bracing members for increased strength in withstanding compressive forces. The upper surface of the base portion may be contoured, e.g. serrated, for improved fixing within the settable material.

[0023] The upwardly extending portion preferably has a structure which is similar to or substantially the same as that described herein with reference to the extender. Thus, the upwardly extending portion preferably has side portions which are connected by at least one resiliently deformable bridge therebetween. The side portions are thus relatively movable towards and away from each other, for example when external lateral forces are applied and released, such as during expansion and contraction of a set slab of material, such as concrete. When external forces press against the side portions the connecting bridge deforms under the pressure, moving the side portions relatively closer to each other, and when the pressure is released, the resilience of the connecting bridge pushes the side portions apart. The connecting bridge preferably deforms in preference to the side portions , which preferably do not substantially deform under the external pressures typically encountered during use . Accordingly, the connecting bridge is preferably either formed from a material which is more easily deformed under pressure compared to the material from which the side portions are formed, or i f made from the same material as the side portions , for example in the case where the screed rail is formed as a s ingle integral piece , the connecting bridge preferably has dimensions which are configured so that it will preferentially deform over the side portions . For example , the connecting bridge may be thinner than the side portions .

[ 0024 ] The upwardly extending portion o f the screed rail may comprise one or more bridges , according to the intended use of the screed rail and the forces to which the side portions are expected to be subj ected during use . For example , the screed rail may comprise one , two , three or more connecting bridges . The bridges may conveniently have a curved crosssection ( e . g . an arc of a circle , such as an approximate C- shape or semicircle ) .

[ 0025 ] The side portions of the upwardly extending portion of the screed rail body extend from a lower end, where they connect to the base portion, and an upper end . The side portions may comprise supporting members extending between their outer surfaces , towards the lower end, and the upper surface of the base portion, for increased structural strength . The lower end portion and/or the upper end portion preferably comprise a recess , forming an elongate channel along some or all the length o f the body . The upper end portion recess is preferably defined by the upper ends of the side portions and optionally the uppermost connecting bridge . The lower end portion and/or upper end portion recesses may for example be used to receive an elongate resiliently compressible member for additional resilience to lateral compressive forces , or a filler material .

[ 0026 ] The upper end of the upwardly extending portion of the screed rail body is preferably configured to engage with the lower end portion of the extender, and may comprise locking means for locking the screed rail and the extender together . For example , one of the upper end of the upwardly extending portion of the screed rail and the lower end portion of the extender may comprise one or more proj ections , and the other may comprise a corresponding receiver to receive the proj ection . For example , the lower end portion of the extender may comprise a receiver channel in at least one of its inner surfaces to receive a corresponding proj ection positioned on at least one corresponding outer surface of the upper end of the upwardly extending portion . The upper end of the upwardly extending portion of the screed rail body may comprise an upper recess into which a downwardly proj ecting member of the lower portion of an extender or cover strip is configured to fit .

[ 0027 ] The modular screed rail system of the second aspect of the present invention optionally comprises a cover strip . The cover strip preferably extends partly or fully along the length of the screed rail and extender and may be releasably positioned over the upper end of the upwardly extending portion of the screed rail and the upper end portion of the extender to prevent ingress of material during use . Preferably, the cover strip can be removed, for example when the material has set . The cover strip may have the form of a U-shaped strip or channel , which can preferably releasably clip over the upper end of the upwardly extending portion of the screed rail and the upper end portion of the extender . For example , the cover strip may comprise releasable engaging means for releasably engaging the cover strip with the screed rail and the extender. For example, the cover strip may comprise one or more projections for engaging with one or more corresponding receiver channels in the upper end of the upwardly extending portion of the screed rail and the upper end portion of the extender, or vice versa. The cover strip may take the form of an elongate tube, having a downwardly extending projection which is configured to fit into an upper recess in the upper end of the upwardly extending portion of the screed rail body.

[0028] The cover strip may be formed from a plastics material, preferably as a single extruded piece. The cover strip may be formed from the same material as the screed rail and/or extender (e.g. UPVC) , or may be formed from a different material, for example a material with greater flexibility, such as a rubber, for ease of attachment and removal.

[ 0029] Additional resilience to lateral compressive forces may be achieved through one or more elongate resiliently compressible members positioned within the screed rail body, for example in one or more channels formed by a connecting bridge and/or the upper end recess and/or lower end recess. The elongate resiliently compressible member may be formed, for example, from a resiliently compressible rubber or sponge (e.g. Neoprene ) .

[0030] The screed rail and one or more extenders are preferably formed from a plastics material, preferably as separate integral pieces, for example plastics extrusions, and may be cut to a desired length on site. For example, the plastics material may be UPVC (unplasticized polyvinyl chloride) .

[0031] Screed rail dimensions vary, and are typically in the region of 2000-3000mm length, 50-150mm in width (base portion) , and 50- 150mm height . The extender may have a height of 25-50mm .

[ 0032 ] The present invention will now be described in detail with reference to the accompanying drawings , in which :

Figure 1 is a front view of a first extender embodiment according to the present invention;

Figure 2 is a perspective view of a portion of the extender of Figure 1 ;

Figure 3 is a front close up view of a plurality of extenders as shown in Figures 1 and 2 connected together with a cover strip ;

Figure 4 is a front view of an embodiment of a modular screed rail system according to the present invention incorporating the plurality of extenders as shown in Figure 3 ;

Figure 5 is a perspective view of a portion of the modular system of Figure 4 ;

Figures 6A, 6B, 6C and 6D are front views of a screed rail which forms part of the modular system shown in Figures 4 and 5 ;

Figures 7A and 7B are perspective views of a fixing means for use with the modular system shown in Figures 4 and 5 in disassembled and assembled states respectively;

Figure 8 is a front view of a first cover strip which optionally forms part of the modular system shown in Figures 4 and 5 ;

Figure 9 is a perspective view of a portion of a screed rail system incorporating the fixing means of Figures 7 A and 7B ;

Figure 10 is a front view of a second extender embodiment according to the present invention;

Figure 11 is a front view of a screed rail which forms part of a second modular screed rail system embodiment of the present invention for use with the extender shown in Figure 10 ;

Figure 12 is a close up view of the part of the screed rail within circle A in Figure 11 ;

Figure 13 is a front view of a second modular screed rail system embodiment of the present invention comprising a single extender as shown in Figure 10 , a screed rail as shown in Figures 11 and 12 , and a cover strip ;

Figure 14 is a front view of the top part of the second modular screed rail system embodiment shown in Figure 13 comprising two extenders ; and

Figure 15 is a front view of a second cover strip which optionally forms part of the modular screed rail system shown in Figures 13 and 14 .

[ 0033 ] It should be noted that for clarity purposes not all the features of the illustrated embodiments of the present invention are identi fied in all of the Figures .

[ 0034 ] As illustrated in Figures 1 and 2 , an extender 1 comprises an elongate body having two side portions 2 . The side portions 2 are connected by two resiliently deformable bridges 7a, 7b having a curved cross-section so as to permit movement between the side portions 2 towards and away from one another when external lateral forces are applied and released .

[ 0035 ] The side portions 2 define an upper end portion 3 and a lower end portion 4 of the extender 1 . The upper end portion 3 comprises an upper recess 5a defined by the upper ends of the side portions 2 and the uppermost connecting bridge 7a . The upper recess 5a is suitable for receiving a filler material or an elongate resiliently compressible member (not shown) . It will be understood that the length Li is only indicative of a particular section of the extender 1 , and in use , the actual length of the extender 1 will be suf ficient as to extend the length of screed rail in its entirety .

[ 0036 ] The lower end portion 4 comprises a lower recess 5b defined by the lower ends of the side portions 2 and internal flanges 5c, the flanges 5c forming pockets 5d . In this way, the lower recess 5b is shaped to receive the upper end portion 3 of another extender 1 . Speci fically, the internal flanges 5c may engage with the upper ends 5e of the side portions 2 to hold two extenders together .

[ 0037 ] In this connection, the extender 1 also comprises locking means comprising proj ections 6a located on the upper end portion 3 and receiver channels 6b located on the lower end portion 4 .

[ 0038 ] A plurality of connected extenders A is illustrated in Figure 3 , wherein the receiver channels 6b of the top extender 1A receives the proj ections 6a of the bottom extender IB such that the extenders 1A, IB are securely locked together .

[ 0039 ] The top extender 1A of the plurality of extenders A is engaged with a removable cover strip 8 , further illustrated in Figure 8 . The cover strip 8 is substantially U-shaped and comprises a top portion 81 j oining together two side portions 82 , 83 . The top portion 81 includes flanges 85 for engaging with the upper recess 5a of an extender 1 and the side portions 82 , 83 include receiver channels 86 for receiving the proj ections 6a of an extender 1 , such that the upper end portion 3 of an extender 1 is releasably engageable with the cover strip 8 .

[ 0040 ] The lower end portion 4 of the extender 1 is also configured to engage with a screed rail 10 to extend its height , as shown in Figures 3 , 4 and 5 . These Figures illustrate a screed rail system 20 according to an embodiment of the present invention comprising a screed rail 10 and the plurality of extenders A. Figure 3 is a close up view of the portion of the screed rail system 20 shown with the circle in Figure 4 . It will be understood that the length L2 in Figure 5 is only indicative of a particular section of the screed rail 10 , and in use , the actual length of the screed rail 10 may be several metres long .

[ 0041 ] The screed rail 10 comprises a base portion 12 and an upwardly extending portion 16 , connected by supporting members 11 . Similarly to when an extender connects to another extender, the flanges 5c of the lower end portion 4 of the extender 1 engage with the upper ends 19 of the upwardly extending portion 16 . Further, the upper end 19 of the upwardly extending portion 16 also comprises proj ections 18 for engaging with the receiving channels 6b of the lower end portion 4 of an extender 1 such that the screed rail 10 and the extender 1 are securely held together .

[ 0042 ] In this way, the upwardly extending portion 16 of the screed rail 10 may also engage with a cover strip 8 , as illustrated in Figure 6D, whereby, the flanges 85 of the cover strip 8 engage with the upper end 19 of the upwardly facing portion 16 of the screed rail 10 and the receiver channels 86 of the cover strip 8 receive the proj ections 18 of the upwardly extending portion 16 .

[ 0043 ] The base portion 12 further comprises parallel serrations 13 on its upper surface for engaging with settable material . The upwardly extending portion 16 comprises side portions 9a, b connected by a series of resiliently deformable bridges 15a, b, c, d, e similar to the structure of the extender 1 . As such, the upwardly extending portion 16 may be compressed when external lateral forces are applied, as shown in Figure 6C, whereby the bridges 15a, b, c, d, e deform such that the side portions 9a, b of the screed rail 10 move towards one another . Once the lateral forces applied to the upwardly extending portion 16 of the screed rail 10 are removed, the side portions 9a, b move away from one another .

[ 0044 ] As also shown in Figure 6A, the screed rail 10 comprises two elongate channels 14 a, b . The upper channel 14a is defined by the upper ends of the side portions 9a, b of the upwardly extending portion 16 and the uppermost bridge 15a, whilst the lower channel 14b is de fined by the lower ends of the side portions 9a, b and the lowermost bridge 15e . The channels 14a, b are shaped to receive elongate resiliently compressible members 17a, b respectively, as shown in Figure 6B .

[ 0045 ] Figure 7A shows an exploded view of a fixing means 25 comprising a cylindrical steel pin 21 , an adj ustable clamp body 22 having a serrated base 221 , and a pair of tapered serrated wedges 23a, b . Figure 7B shows the above components assembled into a working fixing means 25 , wherein the clamp body 22 is adj usted to securely clamp the steel pin 21 and the tapered serrated wedges are positioned back-to-back to form an adj ustable packing block 23 af fixed to the clamp 22 . The clamp 22 further comprises slots 24 , shaped to receive securing means such as a zip tie or wire loop (not shown) to ensure suf ficient clamping to the steel pin 21 .

[ 0046 ] As illustrated in Figure 9 , an embodiment of a modular screed rail system 30 comprises a screed rail 10 and fixing means 25 , as described above . In operation, the serrated base 221 of the clamp 22 interlocks with the corresponding serrations 13 of the base portion 12 of the screed rail 10 such that the screed rail 10 is held in position and correct hori zontal alignment . The steel pin 21 is inserted through a vertically facing aperture 27 in the base 12 of the screed rail 10 . The screed rail 10 also comprises a plurality of hori zontally facing apertures 26 situated in the upwardly extending portion 16 to allow the insertion of dowels or tie bars (not shown) .

[ 0047 ] Turning to the embodiments of the present invention shown in Figures 10 to 15 . an extender 100 comprises an elongate body having two side portions 102 . The side portions 102 are connected by a resiliently deformable bridge 107 having a curved cross-section so as to permit movement between the side portions 102 towards and away from one another when external lateral forces are applied and released . The resiliently deformable member 107 has a downwardly proj ecting member 107a, which is configured to fit within upper recess 105a of another extender 100 .

[ 0048 ] The side portions 102 define an upper end portion 103 and a lower end portion 104 of the extender 100 . The upper end portion 103 comprises an upper recess 105a which is configured to receive the downwardly proj ecting member 107a of another extender 100 .

[ 0049 ] The lower end portion 104 comprises a lower recess 105b defined by the lower ends of the side portions 102 and the resiliently deformable bridge 107 , including downwardly extending member 107a . The lower recess 105b is shaped to receive the upper end portion 103 of another extender 100 .

[ 0050 ] In this connection, the extender 100 also comprises locking means comprising proj ections 106a located on the upper end portion 103 and receiver channels 106b located on the lower end portion 104 .

[ 0051 ] A plurality of connected extenders 100 is illustrated in Figure 14 , wherein the receiver channels 106b of the top extender 100A receive the proj ections 106a of the bottom extender 100B such that the extenders 100A, 100B are securely locked together . The bottom extender 100B is shown in Figure 14 attached to a screen rail 110 , with the proj ections 106a engaging with corresponding receiver channels 118 in the screed rail 110 , with the extender 100 similarly shown connected to screed rail 110 in Figure 13 .

[ 0052 ] The extender 100 shown in Figure 13 and top extender 100A of the plurality of extenders in Figure 14 are engaged with a removable cover strip 108 , further illustrated in Figure 15 . The cover strip 108 is an elongate tube which comprises a top portion 181 and a bottom portion 184 j oining together two side portions 182 , 183 . The bottom portion 184 comprises a downwardly extending member 185 , which corresponds to downwardly extending member 107a of extender 100 , and is configured to fit into an upper recess 105a of an extender 100 or an upper recess 125 of a screed rail .

[ 0053 ] The lower end portion 104 of the extender 100 is also configured to engage with a screed rail 110 to extend its height , as shown in Figures 13 and 14 . These Figures illustrate a second screed rail system 200 according to an embodiment of the present invention comprising a screed rail 110 and one and two extenders 100 , 100A and 100B respectively . Figure 13 thus shows a single extender 100 connected to a screed rail 110 and Figure 14 shows two extenders 100A and 100B connected to a screed rail 110 .

[ 0054 ] The screed rail 110 comprises a base portion 112 and an upwardly extending portion 116 , connected by supporting members 111 . The upper end 119 of the upwardly extending portion 116 also comprises proj ections 118 for engaging with the receiving channels 106b of the lower end portion 104 of an extender 100 such that the screed rail 110 and the extender 100 are securely held together . At the upper end the screed rail 110 comprises an upper recess 125 which is configured to receive the downwardly proj ecting member 107a of an extender 100 , or the downwardly proj ecting member 185 of a cover strip 108 .

[ 0055 ] The base portion 112 further comprises parallel serrations 113 on its upper surface for engaging with settable material . The upwardly extending portion 116 comprises side portions 119a, b connected by a series of resiliently deformable bridges 115a, b similar to the structure of the extender 100 . As such, the upwardly extending portion 116 may be compressed when external lateral forces are applied whereby the bridges 115a, b deform such that the side portions 119a, b of the screed rail 110 move towards one another . Once the lateral forces applied to the upwardly extending portion 116 of the screed rail 110 are removed, the side portions 119a, b move away from one another .

[ 0056 ] It will be appreciated that the speci fic embodiments described herein are for illustrative purposes only, and that further modi fications and variations of the embodiments are possible without departing from the scope of the present invention as defined by the appended claims .