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Connection Details
Careful erection, fixing and strapping is essential if a trussed rafter roof is to provide a sound platform for roof coverings and contribute effectively to the
stability of the roof and gable ends.
 
Strapping gables to ceiling ties
 
Ceiling ti straps may be excluded from the specification for roof pitches below 20 degrees.  Check with the building designer. If they are needed, fix as shown for rafter straps, but attach to the upper edge of the ceiling tie. Use a twisted strap to engage a vertical joint if horizontal courses do not coincide.
 
Strapping at the separating wall

In addition to the normal strapping to walls, additional straps may have been specified to provide longitudinal bracing between roofs, these should be run over the top of the separating wall and fixed to the specified number of trusses on each side. Include noggings and packing to transmit loads properly.
Holding down roofs to walls

Roof to wall (vertical) strapping is not required unless the location of building construction is known to be wind stressed, then it is essential to carry out the roof designer's specifications. Lighter roof coverings in areas of higher wind load require holding down straps as may be specified for brick/block construction. In extreme cases the design may call for direct strapping of rafters to the walls (see figure 54).

Straps are normally 30 x 2.5mm section galvanised steel but any higher specification should e followed. The tops of the straps should be nailed (three 30 x 3.75mm nails or more) to the wall plate, or the rafter in the case of a rafter to wall strap. When fixing to the wall, it is critical that the straps are long enough to run over the specified number of blocks, and that at least two of the fixings engage the last full block at the base of the strap.
 
 
How to fix rafter straps

Engage at least three trusses with each strap. Use galvanised steel straps 30 x 5mm or approved profile galvanised steels straps.