The gable ladder

On trussed rafter roofs no purlin or ridge board exists, therefore alternative means of supporting the overhang are required. The 'gable ladder' is used to provide the roof support (see Fig. 8.12).

The gable ladder can be constructed on site, but is more usually provided either assembled or as a set of precut components by the trussed rafter manufacturer. It is common practice to use the same timbers in framing the gable ladder as are used in the trussed rafters themselves, thus ensuring good alignment of the roof. The gable ladder is a simple nailed assembly, itself nailed through one of the gable ladder rafters directly to the last trussed rafter on the main roof. The brickwork is then built around the 'rungs' of the ladder to fix it securely in place. Significant overhangs beyond the gable end can be achieved using this detail, but beyond about 450 mm particular care must be taken in fixing the gable ladder, ensuring that it is correctly designed to carry not only the load of the roof but also the operative working on the roof. Barge boards can be fixed as previously described and, with the fascia continuing through from the main roof, the typical barge board to fascia detail can be achieved. Wind uplift

Fig. 8.12 Gable ladder - brick/block wall.

on very wide verge overhangs may require the gable ladder to be strapped down to the wall.

On timber framed housing it is quite common practice to use a completely prefabricated verge unit, this comprising the gable ladder, prefixed soffit, and prefixed barge boards. This unit will be nailed, as illustrated in Fig. 8.13, to the last trussed rafter

Barge board

Gable ladder

Compressible filler

Barge board

Gable ladder

Compressible filler

Non-load bearing brick cladding

Timber framed gable end

Fig. 8.13 Gable ladder - timber frame wall.

Non-load bearing brick cladding

Timber framed gable end

Fig. 8.13 Gable ladder - timber frame wall.

of the timber framed house and, supported on the timber framed gable end panel, it will cantilever over to give the desired gable end overhang. The effective cantilever should not exceed 600 mm or the distance from the timber gable panel to the first roof truss if less than 600 mm. This will ensure that the truss does not carry uplift loads from the gable ladder overhang caused by its loading of tiles and wind gust uplift. Refer to Fig. 8.13, 'x' must not exceed 'y'. Care must be taken to ensure a settlement gap between the brickwork skin and the soffit to allow the timber frame to settle independently of the brickwork without disturbing the true roof line. The gap should be filled with a compressible filler.

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