WALL STRUCTURE

Abstract: A crib wall structure comprises a plurality of tiers of stretchers (111) and headers (112) containing in-fill material. The headers (112) in adjacent tiers are in register with each other and each pair of in-register headers (112) is separated at each face of the wall by a stretcher (111). Each tier has a plurality of stretchers (111) aligned along the wall and positioned end to end. Each junction (114) of an adjacent pair of stretchers (111) is a half lap joint (114) in which overlapping tongues (117) of the lap joint have mating surfaces substantially parallel to the face of the wall.

Description: WALL STRUCTURE The present invention relates to a crib wall structure comprising a plurality of tiers of stretchers and headers arranged for containing an in-fill material to form a crib wall. Crib walls are constructed primarily using stretchers, comprising elongate wooden members aligned generally along the length of the wall, arid headers comprising elongate wooden members aligned perpendicular to the general vertical plane of the wall. The headers and stretchers are clipped together to form box-like structures known as cribs. Header support blocks are fitted vertically between the tiers of headers to provide additional support to the headers. The material used is normally of a constant thickness in each of the components, for ease of manufacture. An example of such forms of crib walling is shown in EP-A-0, 136, 124. Each tier of the crib walling has a plurality of stretchers aligned along one or both faces of the wall and positioned end to end. The junctions of the end to end aligned stretchers are conventionally simple butt joints, and are positioned between headers which are spaced apart along the length of the wall, usually mid-way between a pair of headers. A disadvantage of this is that the pressure of the in-fill material in the crib wall often causes the free distal ends of the stretcher butt joints to deflect outwardly, with consequent weakening of the wall and also aesthetically displeasing appearance. In US-A-1 ,749,303 (Rutter) there is disclosed a crib wall structure formed of headers and stretchers. The stretchers are arranged in line along the wall positioned end to end, and are provided with tongues having plane end faces abutting each other. The headers have end tongues adapted to with each abutting pair of stretcher tongues, with the outer end of the header tongues terminating flush with the outer faces of the stretchers. The respective tongues of the stretchers and headers are said to have their meeting faces so arranged as to furnish an interfitting joint adapted to lock the various members against relative movement in four horizontal directions. The joints involved are complex, involving various bevelled faces formed in the tongues so as to lock the structure together. This is necessary because adjacent end to end stretchers are joined by plane abutting surfaces, and because the object of the disclosure is to provide a flush finished face to the wall. The shaped ends of the stretchers and headers are complex, and hence expensive to manufacture. It is an object of the present invention to provide a crib wall with improved strength characteristics and improved aesthetic appearance when in use over a period of time. It is a particular object of the present invention to provide such an improved crib wall which is also simpler and more economical to produce than known arrangements. According to the present invention there is provided a crib wall structure comprising: a plurality of tiers of stretchers and headers arranged for containing in-fill material to form a crib wall having at least one exposed face; the stretchers comprising elongate wooden members aligned generally along the length of the wall and the headers comprising elongate wooden members aligned generally perpendicular to the general plane of the wall; each tier of headers comprising a plurality of headers spaced apart along the length of the wall, the headers in adjacent tiers being in register with each other, each pair of in-register headers being separated at said at least one face of the wall by a stretcher spanning at least two headers in a tier, each tier having a plurality of stretchers aligned along said at least one face of the wall and positioned end to end; in which each junction of a pair of end to end adjacent stretchers in a tier is positioned between and in register with a pair of headers in adjacent tiers, and each said junction of a pair of end to end adjacent stretchers in a tier is a lap joint in which each stretcher at the joint has a protruding tongue of thickness less than the thickness of the stretcher, which overlaps with a corresponding tongue on the other stretcher at the joint. It is particularly preferred that each header extends outwardly beyond its associated stretchers at the said at least one exposed face of the wall, the stretchers being located in cut out portions in the headers, the cut out portions being spaced inwardly from the outer ends of the headers. Preferably each cut out portion has a rectangular cut out having two end faces generally perpendicular to the length of the header and a longitudinal face generally parallel to the length of header. Conveniently each junction of a pair of end to end adjacent stretchers in a tier is a half lap joint, also known as a half butt joint, in which each protruding tongue is substantially half the thickness of the stretcher. However other forms of lap joint may be used. It is preferred that the overlapping tongues at the joint have mating surfaces substantially parallel to the face of the wall. Also it is preferred that each protruding tongue has a length greater than the thickness of the associated pair of in-register headers which are separated by the stretchers at the lap joint, the lap joint being positioned so that the tongues extend beyond the pair of in- register headers on either side thereof. In accordance with another preferred feature, each header is shaped with opposed cut out portions in the region of each end of the header, each pair of adjacent in-register headers of adjacent tiers being separated at at least one face of the wall by a stretcher located in a pair of cut outs of said adjacent in-register headers. Each pair of in-register headers in adjacent tiers may be separated by a stretcher, as set out before, with the other ends of the headers on the other face of the wall being separated by other means. For example at a second face of the wall, opposed to the said at least one face, each pair of in-register headers may be separated by a key block comprising a wooden block spanning only one header in a tier. However it will normally be the case that stretchers are provided on both sides of the crib wall. In accordance with another feature of the invention, it may be arranged that the wall is a retaining wall for retaining material contiguous with one face of the wall, and in such a retaining wall it may preferably be arranged that the headers of adjacent tiers are separated at both faces of the wall by stretchers spanning at least two headers, the thickness of the stretchers on the exposed face of the wall being greater than on the face of the wall contiguous with the retained material. However, it may be required in such arrangements that the thickness of the stretchers on the exposed face of the wall is equal to that on the unexposed face. A number of advantages arise from the present invention, in the use of a lap joint between adjacent end to end stretchers. In general the positioning of the junctions of stretchers in register with adjacent headers gives increased strength, and reduces movement of the distal unsupported ends of the stretchers by the in-fill material. The arrangement avoids gaps opening up between stretchers, and also allows the headers to be spaced more widely apart along the length of the wall. The lap joint arrangement gives added advantages of strength and stability, and also gives a better aesthetic appearance from the front of the wall, if movement longitudinally of the stretchers occurs. If due to movement two adjacent stretchers move apart, the effect of the lap joint is that no unsightly gap appears. In connection with the preferred feature of the invention of different thicknesses of front and back stretchers in a retaining wall, this arrangement takes account of the different design loadings which are applicable to the front and back stretchers, and allows the thickness to be adjusted accordingly. The variation of the thickness of the stretcher from front to back stretchers (with the thicker at the front and the thinner at the back) means that these can be made more economically. The more heavily loaded front stretcher (with unsupported outer edge) needs to be heavier than the rear which is buried and surrounded by in-fill, for example stone in-fill. However it is to be appreciated that although the invention finds application particularly in retaining walls, the invention may also be used in a vertical free standing wall, for example for sound and visual barrier systems. In accordance with another aspect of the present invention, there may be provided a crib wall structure comprising a plurality of tiers of stretchers and headers arranged for containing in-fill material to form a crib wall; the stretchers comprising elongate wooden members aligned generally along the length of the wall and the headers comprising elongate wooden members aligned generally perpendicular to the general plane of the wall; each tier of headers comprising a plurality of headers spaced apart along the length of the wall, the headers in adjacent tiers being in register with each other, each pair of in-register headers being separated at at least one face of the wall by a stretcher spanning at least two headers in a tier, each tier having a plurality of stretchers aligned along said at least one face of the wall and positioned end to end; in which each junction of a pair of end to end adjacent stretchers in a tier is a lap joint in which each stretcher at the joint has a protruding tongue, of thickness less than the thickness of the stretcher, which overlaps with a corresponding tongue on the other stretcher at the joint. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a perspective view of one face of a crib wall, as previously known; Figure 2 is a perspective view of a know crib wall structure which may form part of a crib wall as shown in Figure 1 ; Figure 3 is a plan view from above of the known crib wall of Figure 1 , after use for some period of time; Figure 4 is a perspective view of part of a crib wall structure embodying the present invention; Figure 5 is a plan view from above of a junction of stretchers shown in Figure 4; Figure 6 is a perspective view of a crib wall embodying the invention, in elevation; Figure 7 is a plan view from above of a crib wall embodying the invention; and Figures 8 and 9 are plan views of alternative junctions between stretchers which may be used in place of the junction of Figure 5. With reference to Figures 1 , 2 and 3, a known crib wall is formed from a plurality of tiers of stretchers 11 and headers 12 arranged in a box like structure for containing in-fill material 13, also known as back-fill. The filling material within wall should be crushed quarried rock that will not break down under weathering, of sufficient stone size to be free draining without washing out of the wall face, but small enough not to damage or displace timber components. Well graded material (containing a good mix of intermediate sizes) between 20mm and 100mm stone size is considered ideal. As seen in Figures 1 and 2, the stretchers 11 comprise elongate wooden members aligned generally along the length of the wall 10, and the headers 12 comprise elongate wooden members aligned generally perpendicular to the general plane of the wall 10. Each tier of headers 12 comprises a plurality of headers spaced apart along the length of the wall, the headers 12 in adjacent tiers being in register with each other, one above the other. As shown in Figure 2, each pair of in-register headers 12 is separated at each face of the wall by a stretcher 11 which spans two headers 12 in each tier. As seen in Figure 1 , each tier has a plurality of stretchers 11 aligned along the face of the wall, and positioned end to end. Each pair of stretchers 11 meets at a simple end on butt joint 14 which is positioned mid-way between a pair of headers 12. As shown in Figure 2, each header 12 has at each end thereof a pair of opposed cut-out portions 15, to accommodate the stretchers 11 which separate the tiers of headers 12. Between each pair of in-register headers 12 in adjacent tiers, is positioned a header support block 16 which assists in preventing crushing of the crib work by the weight of the upper tiers and the in-fill material. The header support blocks 16 may be omitted in the upper part of the wall, according to design requirements. Figure 3 shows the problem which may arise with a known crib wall such as has been described. Because the butt joint of end to end stretchers 11 is positioned mid-way between adjacent headers 12, the distal end of each stretcher is cantilevered from the header which supports it, to the central point between the headers. This can give rise to deflection of the distal ends of the stretchers 11 as shown at the junctions 14A, 14B and 14C. Other difficulties which arise in this known design is that if deflections and shrinkage occurs in the cantilevered stretcher 11 this can give rise to gaps occurring between distal ends of adjacent stretchers, and loss of alignment of the stretchers. This gives an aesthetic disadvantage in that the gaps and loss of alignment are unsightly. Referring now to Figures 4 to 7, there is shown a crib wall embodying the invention which overcomes or diminishes the disadvantages mentioned. In general in these Figures like reference numerals are used for components which correspond to those described in the previous Figures. As shown, the crib wall 110 in Figure 6 is made from a plurality of tiers of stretchers 111 and headers 112 arranged generally in the same manner as in a known crib wall. However, as shown in Figure 4, each junction 114 of adjacent stretchers 111 is a half lap joint (also known as a half butt joint), and is positioned between and in register with a pair of in-register headers 112. As shown in Figure 5, each junction 114 of a pair of stretchers 111 is a lap joint in which each stretcher 111 has a protruding tongue 117 which overlaps with a corresponding tongue 1 17 on the other stretcher at the joint. In this particular example, each tongue 1 17 is of a thickness half the thickness of the stretcher 111 , although in other arrangements this may be varied. The lap joint 114 is arranged so that the mating surfaces of the two tongues 117 are substantially parallel to the face of the wall, that is to say approximately vertical. As shown particularly in Figures 4 and 5, each junction 114 is positioned so that the centre of the junction, half way along each tongue 117, is positioned in line with a central axis of the associated header 112. Also, each protruding tongue 117 has a length greater than the thickness of the associated pair of in- register headers 112 so that the tongues 117 extend beyond the pair of in- register headers 112 on either side thereof. Each of the headers 112 is shaped with opposed cut out portions 115 in the region of each end of the header, and each junction 114 of adjacent stretchers 111 is located in a pair of cut-outs 115 of the associated headers. Each header 112 extends outwardly beyond its associated stretchers 111 at the exposed face 119 of the wall. The stretchers are located in the cut out portions 115 in the headers, the cut out portions being spaced inwardly from the outer ends of the headers. Each cut out portion 115 is a rectangular cut out having two end faces generally perpendicular to the length of the header and a longitudinal face generally parallel to the length of header. The dimensions of the cut outs correspond to the dimensions of a cross section of a stretcher so that the lap joint of two adjacent stretchers fits into the cut outs of adjacent headers. Figure 4 also shows a preferred feature of the invention, which is used when the retaining wall 110 is designed to be a retaining wall for retaining material contiguous with the rear face of the wall, as shown in Figure 7. In such a case, it is preferred that the thickness of the rear stretchers 111 on the front, exposed face 119 of the wall, are of greater thickness than the stretchers on the rear face 120 of the wall which is contiguous with the retained material. Because the strength requirements are different for the front and rear stretchers, the design of the rear stretcher is for it to be of lesser thickness than the front. This allows savings of material. The more heavily loaded front stretchers, having an unsupported outer edge, needs to be heavier than the rear which is buried and surrounded by stone in-fill. As shown in Figure 7, the positioning of the half butt joints 117 in the region of the headers 112 reduces the likelihood of deflection of the distal ends of the stretchers. Another advantage is that if any shrinkage occurs, the half lap joint gives the appearance of continuity of the front of the wall, as no gap between simple abutting ends is visible. Furthermore, as shown in Figure 7 compared with Figure 3, it is possible to increase the spacing of the headers 112 along the length of the wall, in embodiments of the present invention. There is less likelihood of deflection of the ends of the stretchers, so that it is possible for the stretcher to extend over more than two headers. Figures 8 and 9 show alternative forms of lap joint which may be provided between adjacent stretchers 111. In Figure 8 the joint 114 is made by fingers 117 of adjacent stretchers overlapping, but with each finger having a tapered thickness reducing towards its distal end. In Figure 9, each finger 117 of a joint 114 has a stepped configuration with its thickness diminishing in steps towards its distal end.

Claims: CLAIMS 1. A crib wall structure comprising: a plurality of tiers of stretchers (111) and headers (112) arranged for containing in-fill material to form a crib wall (110) having at least one exposed face (119); the stretchers (111) comprising elongate wooden members aligned generally along the length of the wall and the headers (112) comprising elongate wooden members aligned generally perpendicular to the general plane of the wall; each tier of headers (112) comprising a plurality of headers spaced apart along the length of the wall, the headers in adjacent tiers being in register with each other, each pair of in-register headers being separated at said at least one face of the wall by a stretcher spanning at least two headers in a tier, each tier having a plurality of stretchers aligned along said at least one face of the wall and positioned end to end; in which each junction (114) of a pair of end to end adjacent stretchers (111) in a tier is positioned between and in register with a pair of headers (112) in adjacent tiers, and each said junction (114) of a pair of end to end adjacent stretchers (111) in a tier is a lap joint in which each stretcher at the joint has a protruding tongue (117), of thickness less than the thickness of the stretcher, which overlaps with a corresponding tongue on the other stretcher at the joint. 2. A crib wall structure according to Claim 1 , in which each header (112) extends outwardly beyond its associated stretchers (111) at the said at least one exposed face (119) of the wall, the stretchers being located in cut out portions (115) in the headers, the cut out portions being spaced inwardly from the outer ends of the headers. 3. A crib wall structure according to Claim 2, in which each cut out portion (115) has a rectangular cut out having two end faces generally perpendicular to the length of the header and a longitudinal face generally parallel to the length of header. 4. A crib wall structure according to Claim 3, in which the overlapping tongues (117) at the joint have mating surfaces substantially parallel to the said outer face (119) of the wall. 5. A crib wall structure according to Claim 4, in which each protruding tongue has a thickness equal to substantially half the thickness of the stretcher. 6. A crib wall structure according to Claim 2, in which each protruding tongue (117) has a length greater than the thickness of the associated pair of in-register headers (112) which are separated by the stretchers (111) at the lap joint (114), the lap joint being positioned so that the tongues extend beyond the pair of in- register headers on either side thereof. 7. A crib wall structure according to Claim 1 , in which the wall comprises a retaining wall for retaining material contiguous with one face of the wall, in which the headers of adjacent tiers are separated at both faces of the wall by stretchers spanning at least two headers, the thickness of the stretchers on the exposed face of the wall being greater than on the face of the wall contiguous with the retained material. 8. A crib wall structure according to Claim 7, in which at a second face of the wall, opposed to the said at least one face, each pair of in-register headers are separated by a key block comprising a wooden block spanning only one header in a tier. 9. A crib wall comprising a crib wall structure according to Claim 1 together with in-fill material contained in the crib wall structure. 10. A crib wall structure according to Claim 1 , in which the overlapping tongues (117) at the joint have mating surfaces substantially parallel to the said outer face (119) of the wall. 11. A crib wall structure according to Claim 10, in which each protruding tongue has a thickness equal to substantially half the thickness of the stretcher. 12. A crib wall structure according to Claim 1 , in which each protruding tongue (117) has a length greater than the thickness of the associated pair of in-register headers (112) which are separated by the stretchers (111) at the lap joint (114), the lap joint being positioned so that the tongues extend beyond the pair of in- register headers on either side thereof.

Inventors: O'BRIEN GERALD, WILKINSON JOHN, O'BRIEN, GERALD, WILKINSON, JOHN
Applicants: BRIEN GERALD O, PHI GROUP LTD, WILKINSON JOHN, O'BRIEN, GERALD, PHI GROUP LIMITED, WILKINSON, JOHN
Application year: 2001
Main classification: E02D29
IPC codes: E02D29