Page 30 - Build 165

DETAILS OF UPGRADED FIXINGS FOR VERANDA RAFTERS
BUILD
Veranda rafter xings
The BRANZ helpline often gets asked about xings for veranda rafters. These are not covered in NZS 3604:2011, but BRANZ has some advice.
RIGHT
BY ROGER SHELTON,
BRANZ SENIOR STRUCTURAL ENGINEER
FIXINGS FOR ORDINARY RAFTERS are covered in NZS 3604:2011 Timber-framed buildings, as are veranda beams and posts.
Veranda rafters generally span between a ribbon plate attached to the wall of the building and a veranda beam and may overhang the veranda beam by up to 750 mm depending
on the size of the rafter. Wind uplift loading under such veranda overhangs is higher than
for ordinary rafters so the rafter xings in
NZS 3604:2011 Table 10.1 may not be adequate for some situations.
Use Table 10.1 with these adjustments
Having considered the likely veranda con gura- tions within the overall scope of NZS 3604:2011, BRANZ advice to builders and designers is to use Table 10.1 but with the following adjustments:
● Where the veranda rafter spacing is:
• 1200 mm or more, xing to the veranda beam should be type F rather than type
E as shown in Table 10.1 — an alternative xing with a capacity of 7.0 kN would also be suitable
• less than 1200 mm, no adjustment is required.
● Rafter xings to a ribbon plate may be made using Table 10.1 without further adjustment.
● The ribbon plate should be the same size
as the rafter and xed to each stud with
2/14 gauge screws. Screw length should be su cient to pass through the ribbon plate and cladding and penetrate at least 45 mm into the stud.
roo ng
veranda rafter
rafter plate xed with 2/14 gauge screws penetrating minimum 45 mm into stud
rafter spacing
purlin
veranda beam
post
Veranda rafter xing to beam when rafter spacing is:
≥1200 mm – use type F rather than type E (NZS 3604:2011 Table 10.1) or minimum 7.0 kN xing capacity <1200 mm – follow NZS 3604:2011 Table 10.1
Figure 1
Veranda rafter xing.
28 — April/May 2018 — Build 165