Patent Publication Number: US-7900409-B2

Title: Lintel configuration

Description:
RELATED APPLICATIONS 
     The present application is based on, and claims priority from, Australian Application Number 2007901384, filed Mar. 16, 2007, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lintel configuration within a wall frame for use in building construction. 
     2. Description of the Prior Art 
     Wall frames for building construction, particularly for domestic buildings, are commonly prefabricated in a factory and then transported to site for speedy erection. A prefabricated wall frame will usually consist of one or more window, door or other openings to receive a prefabricated window or door frame which is installed or finished on site. Each such opening is spanned along its upper edge by a lintel to carry the loading applied to the top plate of the wall frame by trusses or other building components above the lintel.  FIG. 1  shows a typical lintel configuration within a prefabricated wall frame. The portion of the frame shown in that Figure has a vertical jamb stud  2 , a vertical prop stud  4  immediately adjacent the jamb stud, a horizontal top plate  6 , and an additional horizontal top plate  8  above that. The lintel  10  spanning the door or window opening extends across the underside of the top plate  6  and is supported at its lower edge by the prop stud  4 . The lintel in this case is formed by a wooden beam but it may alternatively be formed by a metal beam such as a light steel beam of channel cross-section. It will be noted that the prop stud  4  needs to be cut to a shorter length than the jamb stud  2  in order to support the underside of the lintel  10  and this is inconvenient in a factory situation involving the assembly of multiple frames where it is desirable to standardise to the maximum extent possible the pre-cut components needed to assembly the various frames. 
     In this case the prop stud  4  provides the majority of the support for the lintel with some load being transferred to the jamb stud  2  by virtue of the connections (usually nails) between the two. However, the jamb stud  2  mainly serves to provide continuity between the prop stud  4  and the top plate and has minor load bearing capacity. Since the prop stud  4  resists higher loads than the jamb stud  2  or the common studs in the wall frame, apart from being a different length it may need to be of a higher grade which is an added complication in the manufacturing process as it is then necessary to access a different grade of timber and to ensure that it is installed in that particular location in the frame. The increase in grade of the prop stud  4  may not always be sufficient to withstand the magnitude of the applied load and the prop stud  4  may have to be doubled or tripled. Without significant fixing between the prop stud  4  and the jamb stud  2  it is not possible to take advantage of the unused strength of the jamb stud  2 . 
     Moreover, as would be understood, the stiffness of a lintel in the direction of the applied load (a vertical loading) is determined to a significant extent by its depth and with the configuration illustrated in  FIG. 1  its depth is inherently limited by the height of the opening it is spanning and by the overall height of the wall frame and as a result, for increased stiffness to resist deflection, a substantial increase is needed in the thickness or bulk of the beam or in the grade or type. While an increase in the depth of the lintel could be achieved by removal of the top plate in the zone of the lintel, this leads to reduced lateral stability of the frame and also leads to other difficulties in the overall construction of the frame and is not a particularly desirable approach to achieving required lintel strength. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a timber wall frame for use in building construction, the wall frame having at least one window and/or door opening defined by a stud at each side of the opening and a lintel spanning the upper side of the opening, wherein the lintel is of sheet metal, the lintel having a vertical wall and a horizontal flange along an upper edge of the vertical wall, and wherein the lintel is applied to the frame so that its vertical wall overlies a face of each stud and a face of a first top plate of the wall frame, with the flange of the lintel being above the top plate. 
     In the preferred embodiment of the invention, the wall frame has an additional top plate supported by the first top plate, and the opening is defined at each side by a prop stud which is immediately adjacent to a jamb stud, the prop studs and jamb studs extending to the underside of the first top plate. The vertical wall of the lintel extends across the faces of the prop studs and jamb studs and is secured thereto preferably by screwing through the vertical wall of the lintel. 
     In one embodiment, the sheet metal lintel is in the form of a beam having upper and lower flanges of double thickness construction with a hollow interior, the upper flange resting on the upper side of the first top plate with the upper side of the flange being approximately level with the upper side of the additional top plate omitted in the zone of the lintel. In another embodiment, the sheet metal lintel is of single thickness construction and its upper flange rests against, and is secured to, the upper side of the top plate or the additional top plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: 
         FIG. 1  depicts a lintel configuration within a prefabricated wall frame according to a known embodiment. 
         FIG. 2  is a view from the front of a portion of a wall frame having a lintel configuration in accordance with the invention; 
         FIG. 3  is a sectional end view equivalent to  FIG. 2 ; 
         FIG. 4  is a view similar to  FIG. 2  but showing an alternative lintel configuration in accordance with the invention; 
         FIG. 5  is a sectional end view equivalent to  FIG. 4 ; and 
         FIGS. 6A and 6B  are views showing preferred forms of end cut for the lintel. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIGS. 2 and 3 , the lintel  12  is formed by a so-called light steel beam which is a beam of channel section formed from rolled steel strip with rolled flanges of hollow section completed by welding the steel strip during rolling into the required shape, the two flanges thereby effectively being of double thickness construction. The lintel  12  is applied so that its upper flange  12   a  overlies the top plate  6  of the frame and is fixed to the top plate typically by screwing. The additional top plate  8  is omitted in the zone of the lintel and the upper side of the lintel is approximately level with the upper side of the additional top plate at either end of the lintel. With this configuration the prop stud  4  extends to the underside of the top plate  6  and is therefore of the same length as the jamb stud  2  so that studs of appropriate length can be cut for use either as prop studs or jamb studs. The lower flange  12   b  of the lintel is cut back as shown in  FIG. 2  (with a corresponding cut back being made at the other end of the lintel) so that the lower flange  12   b  will fit between the opposed prop studs  4  defining the opening. The vertical wall of the lintel  12  is secured at each end to the adjacent jamb stud and prop stud typically by screwing. 
     The ability to use prop studs and jamb studs of the same length is of significant benefit in a factory situation where many wall frames of the same height are being fabricated. In particular, to enhance productivity and reduce the skill levels required, multiples of common studs can be used to form the prop stud and jamb stud combination. Moreover, the lintel is easily and quickly applied to the frame by laying it over the top plate and the studs and screwing to the frame and this is a more straightforward process than that involved in mounting the lintel in the configuration of  FIG. 1  as the configuration ensures that the lintel will lie flat against the face of the frame. It will also be noted that for a given height of wall frame and height of the opening spanned by the lintel, the depth of the lintel can be maximised as the upper surface of its upper flange is approximately level with the uppermost extent of the wall frame thus making optimum use of the available depth of the lintel. 
     The presence of the upper flange of the lintel on the top plate replaces the additional top plate in the zone of the lintel. In many cases a significant part of the length of a wall frame can be taken by window and door openings and the omission of the additional top plate in the zone of the lintels results in cost savings. 
     In the embodiment shown in  FIGS. 4 and 5 , the lintel  14  is a rolled steel lintel of L-section whereby its flange  14   a  is just of single thickness construction in contrast to the construction of the flanges of the lintel  12 . The lintel  14  is applied over the frame with its flange  14   a  lying against the upper side of the additional top plate  8  and secured to the additional top plate  8  typically by screwing. The vertical wall of the lintel  14  is secured at each end to the jamb stud  2  and prop stud  4  by screwing. As with the embodiment of  FIGS. 2 and 3 , the prop stud  4  and jamb stud  2  are of the same length and the application of the flange of the lintel over the top plate, in this case the additional top plate  8 , enables the depth of the lintel to be maximised. Alternatively it could be applied with the upper flange lying against the upper side of the top plate  6 . 
     In a modification, the lintel  14  has a second flange along its lower edge and in that case the lower flange will be cut back at each end to lie adjacent the inside face of the prop stud in a similar manner to that shown in  FIG. 2 . The lintel with the lower flange will have greater bending resistance and hence an increase in uplift capacity to the L-sectioned lintel shown in  FIGS. 4 and 5 . 
     Whereas the prior lintel configuration described with reference to  FIG. 1  requires the lintel to be cut to a very precise length to ensure it is a tight fit between the jamb studs to permit securing by nailing through the jamb studs into the lintel, the precise fit does not need to occur with the lintel configurations of the preferred embodiments described with reference to  FIGS. 2 to 5 . With the configuration of  FIGS. 4 and 5  absent the lower flange, variation in longitudinal placement and overall length can be tolerated. For the configuration shown in  FIGS. 2 and 3  and a configuration similar to that of  FIGS. 4 and 5  but with a lower flange, the cut back into the lower flange to enable it to locate between the prop studs does not have to be undertaken with sufficient accuracy to provide a tight fit. 
     With the configurations discussed above which require the lower flange to be cut back to locate between the prop studs, it is preferred to cut the ends of the lintel so that the vertical cuts through the upper and lower flanges are offset laterally by a distance corresponding to the combined width of the prop and jamb studs; examples of such a cut are illustrated in  FIGS. 6A and 6B  for the lintel  12 . In this regard, the lintels will typically be cut to the required length from a longer length of stock material. An end cut such as those represented by C in  FIGS. 6A and 6B  will provide the lower flange cut back in two adjacent lengths of lintel without wastage of material as the general symmetry of the cut will produce the same cut back in the two adjacent lintels when installed and which will require inversion of the left hand lintel from the orientation shown. 
     The embodiments have been described by way of example only and modifications are possible within the scope of the invention. 
     Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.