It is known to provide a roof truss which includes a lower chord member extending, in use, in a substantially horizontal direction and two upper chord members connected to the lower chord member intermediate longitudinal ends of the upper chord members.

Each upper chord member extends at an acute angle to the lower chord member and the arrangement is such that the lower chord member and the two upper chord members define a substantially A-shaped frame. Also generally provided are link portions, each link portion extending between the lower chord member and an adjacent upper chord member for providing the roof truss with extra strength.

Such roof trusses are generally constructed of elongate members having a substantially C-shaped cross section.

In use, the roof truss locates relative to an outer wall of a building such that the lower chord member rests on the outer wall at locations on the lower chord member adjacent connection locations between the lower chord member and the adjacent upper chord members. Free end portions of the upper chord members define cantilevered eave portions which extend outwardly beyond the outer wall.

With such a roof truss, it is known that points of weakness exist at locations where the lower chord member is connected to the upper chord members. This is because, in use, at each such connection location the outer wall acts as a fulcrum, and the weight of the respective eave portion tends to effect bending of the upper chord member about the fulcrum. As a result, it is necessary to provide an upper chord member which is

sufficiently strong to withstand the tendency to bend about the abovementioned point of weakness. This has hitherto been achieved by choosing chord members having a web thickness which is sufficient to ensure that the chord members have the required strength.

The present invention seeks, among other things, to provide a chord member for a roof truss which improves on such chord members known hitherto.

The present invention also seeks to provide a method of constructing a chord member for a roof truss which provides a chord member for a roof truss which is improved relative to such chord members known hitherto.

In accordance with one aspect of the present invention there is provided a chord member for a roof truss, characterised in that the chord member includes an elongate first member having an elongate receiving portion, and an elongate second member received in the said receiving portion, an average longitudinal dimension of the second member being less than an average longitudinal dimension of the first member and the second member being received in the said receiving portion at a location relative to the first member such that, in use, when the roof truss is fitted to a building the second member locates adjacent and upwardly of a supporting wall portion of the building.

In accordance with a second aspect of the present invention there is provided a method of constructing a chord member for a roof truss, characterised by including the steps of providing an elongate first member having an elongate receiving portion, providing an elongate second member receivable in the said receiving portion, an average longitudinal dimension of the second member being less than an average longitudinal dimension of the first member, and locating the second member in the receiving portion at a location relative to the first member such that, in use, when the roof truss is fitted to

a building the second member locates adjacent and upwardly of a supporting wall portion of the building.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic perspective view of a portion of a roof truss including a chord member in accordance with the present invention ; Figure 2 is a diagrammatic side view of a portion of a roof truss including a chord member in accordance with the present invention; and Figure 3 is a diagrammatic cross sectional view taken along the line III-III of Figure 2 in the direction of the arrows.

Referring to the drawings, there is shown a portion of a roof truss 10, each half of the roof truss 10 including a chord member in accordance with the present invention in the form of an upper chord member 12, the upper chord member 12 being connected to a lower chord member 14. The upper and lower chord members 12,14 are connected together so that each upper chord member 12 subtends an acute angle with the lower chord member 14 and so that the upper and lower chord members 12,14 together define a substantially A-shaped frame. The A-shaped frame includes a substantially triangular shaped portion 15 and at each leg of the A-shaped frame a cantilevered eave portion 17.

Each upper chord member 12 includes a first elongate chord member 18 and a second elongate chord member 20. The first chord member 18 includes a first elongate base member 22 and first and second elongate side members 24 and 26 respectively extending from opposite longitudinal sides of the first base member 22 in a direction substantially perpendicular to the first base member 22. The first chord member 18 also includes first and second elongate lip members 28 and 30 respectively, each lip member

28,30 extending in a direction substantially parallel to the first base member 22 and substantially perpendicular to the first and second side members 24,26. The first chord member 18 is configured such that a transverse cross section of the first chord member 18 is substantially C-shaped. The first chord member is also configured such that the first base member 22, the first and second side members 24,26 and the first and second lip members 28,30 define a receiving portion.

As shown in Figure 2, the first chord member 18 is connected to the lower chord member 14 at a region of intersection 19 by any suitable fixing means, for example by a weld.

As best seen in Figure 3, the second chord member 20 includes a second elongate base member 32 and first and second elongate arm members 34 and 36 respectively extending from opposite longitudinal sides of the second base member 32 in a direction substantially perpendicular to the second base member 32. The second chord member 20 is configured such that a transverse cross section of the second chord member 20 is substantially C-shaped. The second chord member 20 is also configured such that the second chord member 20 is receivable in the receiving portion of the first chord member 18 as shown, in particular, in Figures 1 and 3.

The second chord member 20 locates in the receiving portion of the first chord member 18 adjacent the region of intersection 19 between the upper chord member 12 and the lower chord member 14, the effect of which is that, in use, when the roof truss is fitted to an outer wall 42 of a building as shown in Figure 2, the second chord member 20 locates adjacent and upwardly of an outer wall 42 and a point of weakness of the upper chord member 12 adjacent the region of intersection 19 is thereby strengthened.

Although not shown in the present invention, the second chord member may alternatively extend to a free end of the eave portion 17.

The second chord member 20 is fixed in position relative to the first chord member 18 by spot welds 38. However, it will be appreciated that the first and second chord members 18,20 may be connected to each other by any other suitable fixing means, for example by a tek fixing.

In the present example, a link 16 extends between each upper chord member 12 and the lower chord member 14, the link 16 being connected to the upper and lower chord members by fixing means 40, which may be a nut and bolt arrangement or a tek fixing or any other suitable fixing means.

The roof truss 10 including the upper chord member 12 in accordance with the present invention is shown in use in Figures 2 and 3. As can be seen, in use, the roof truss 10 locates relative to an outer wall 42 of a building such that the region of intersection 19 between the upper and lower chord members 12,14 locates adjacent an upper portion of the outer wall 42 and the cantilevered eave portion 17 extends beyond an outer surface 44 of the outer wall 42.

The upper chord member 12 is constructed by locating the second chord member 20 in the receiving portion of the first chord member 18 such that the first and second side members 24,26 and the first and second arm members 34,36 extend from their respective first and second base members 22,32 in opposite directions as shown in Figure 3. The second chord member 20 is positioned relative to the first chord member 18 such that the region of intersection 19 between the upper and lower chord members 12,14 is disposed generally intermediate longitudinal ends of the second chord member

20. The second chord member 20 is then fixed relative to the first chord member 18 by any suitable fixing means, for example by spot welds 38.

It will be appreciated that although the present invention has been described with reference to chord members of substantially C-shaped cross section, the invention is equally applicable to chord members of other cross-sectional shapes, the important aspect being that the first chord member of the upper chord member is shaped so as to define an elongate receiving portion and the second chord member of the upper chord member is shaped so as to be receivable in the first chord member, the second chord member thereby strengthening the upper chord member at a region between the longitudinal ends of the second chord member.

It will also be appreciated that by providing a roof truss with an upper chord member in accordance with the present invention, it is not necessary to construct the upper chord member from a web which has a thickness sufficient to overcome forces which tend to bend the upper chord member at the region of intersection. Instead, a web of relatively smaller thickness and therefore lower cost can be used, the point of weakness having been strengthened by the second chord member.

Modifications and variations such as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.