Civil Engineering Reference
In-Depth Information
single-storey building) below. Because of its length this prop should be a scaffold tube fit-
ted with a suitable clip to lock it on to the ridge collar, and restrained at the bottom by tim-
bers laid flat and nailed to the floor joists, or fitted tight against a cross wall. Apart from
this precautionary measure resulting from the weight of the trusses, the other items of bra-
cing can be considered as for the traditional roof described above.
The Trussed Rafter Roof
Bracing for the trussed rafter roof has been fully described in Chapter 5 because of its in-
clusion in BS 5268: Part 3 which was analysed in that section, and because of the trussed
rafter's dependence upon the bracing system for its overall structural integrity.
Hip Roofs
Hip roofs are essentially well braced structures by virtue of the hip board diagonal braces
inherent in the design.
Again referring to Fig. 7.21, binders G and H should be fitted to the section between the
hip ends and as far into the hip ends as possible. Diagonal K should also be fitted and, un-
less the distance between the hip peaks is very long, diagonal F should not be required.
Valley Intersecting Roofs
Each roof section should be treated individually with the guidance set out above. The val-
ley boards themselves add extra diagonal stiffening in that area. The discontinuity of tile
battening under the abutting roof should be replaced by timber binders placed on top of
the common rafters as described in trussed rafter valley roofs in Chapter 6.
Attic Roofs
Attic roofs, because of their great height and the inherent large void forming the rooms,
present their own particular problem with regard to bracing. The trussed rafter attic has
been dealt with in some detail in Chapter 5. It is unlikely that an attic will be constructed
using bolt and connector principal trusses. The notes below therefore apply to traditionally
constructed attics and also generally to trussed rafter attic roofs, although in the latter case
specific designs for bracing should be obtained from the truss designer.
