![]() Note that these are normally only required to trussed rafter roofs and not for traditional purlin and rafter roof construction. Most areas exceeding 100m but not exceeding 200m (refer to BS 6399-3): 1 kN/m² snow load & 0.9 kN point load. The lower section is a true valley, with a valley rafter between a rafter beam and the sub-ridge, and the upper part is a layover valley. Imposed loads (roof snow load and short-term point load) Altitude not exceeding 100m: 0.75 kN/m² snow load & 0.9 kN point load. This chart is for intersections of equal pitch ONLY. The challenging part is that the sub-ridge brakes the valley line into two sections. This chart is for initial rough sizing hip and valley rafters, work should be checked by an engineer before plans are finalized. We choose to include w k.I -0. ![]() In case you need to brush up on it you can read the blog post here. This is the right way to fix truss clips connecting the rafter and wall plate. The valley between the north and east roofs is a common valley, with the intersecting roofs at the same 10-in-12 pitch. Luckily we have already written an extensive article about what load combinations are and how we use them. Vertical strapping at eaves pitched roofsĪt eaves level, vertical straps 1m long should be fixed as shown in the diagram opposite at a maximum of 2m centres. Effective strapping at gable wallĮach strap should be fixed as shown in the diagram opposite with noggins between the rafters to support the metal strap along its whole length. Gable walls need to be strapped to the roof at the maximum 2m centres using 30 x 5m galvanised mild steel straps. This diagram illustrates the typical arrangement of a rafter and purlin roof and shows the dimensions referred to in the tables above. Roof pitch between 30 and 45 degrees strength class C24 Size of purlins in mm ![]()
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