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Bearing Details
Consideration should also be given to protecting the timber and fasteners against dampness and aggressive ingredients in the mortar by using a dpc between truss and masonry. Trusses can also be supported off the face of a wall by use of suitable hangers. The installation
instructions should be noted especially concerning the minimum height of masonry above the hanger flange and the maximum gap between the end of the trusses and the back plate of the hangers. The effect of the eccentric loading on walls loaded in this way should also be assessed.
Top hung fixings (figure 84j) are not common since, at ceiling level, the wall generally needs lateral restraint from the roof against wind and the ceiling ties need to be stabilised.
Flat topped girders supporting trusses (figure 85) can be supplied with a shaped fillet (figure 85a); or trusses may have a wedge or block plated into the joint to provide a horizontal bearing surface (figure 85b).