We now look at a hip which overlays the valley. This presents its own special problems and cannot be solved with the designs illustrated thus far. Unlike a normal intersection, in which a full height girder can be used where the hip overlays the main roof to some degree, the depth available for the main roof truss supporting girder is drastically reduced. The solution illustrated in Fig. 7.11 uses a flat top girder truss to support both the main roof trussed rafters and the hip monos. Prefabricated frames form the valley and carry the upper part of the hip construction, these being supported off the trussed rafters. There is no major problem with the additional imposed load of the frames themselves as the principle load is from the tiles, and there is no greater area of tiling than there would be had the hip not been imposed. The hip would be completed with a short length of ridge board running from the peak of the hip to the main roof itself. This hip board could either be supported on a trussed rafter if positioned in line with the peak of the ridge of the hip, or on the valley lay boards themselves supported by a trimmer between the trussed rafters at that point. These latter items have been omitted from this particular illustration for clarity, but similar details can be found in Chapter 3 on traditional roof construction.
Fig. 7.11 Overlaid hip - valley intersection.
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