Page 35 - Build 151

joist
centreline of joist
90 mm wide frame can have 45 mm packers between the loadbearing joists (see Figure 3).
Clause 7.1.3.2 also requires any trimming studs that land on doubled joists to be within 300 mm of the end of the span of the doubled joist (see Figure 4).
Is support required for non-loadbearing walls parallel to the joists? Non-loadbearing walls that do not have braced panels and are within 150 mm of a oor joist don’t require additional support.
However, 90 × 45 mm blocking on edge (i.e. 90 mm high) is required to be installed between adjacent joists at each side of door openings (see Figure 5).
Support is required where the non-loadbearing wall contains bracing or is more than 150 mm from the joist. Place 90 × 45 mm blocking on edge between the joists at 1200 mm centres and each end of the frame supported. Alternatively, place the wall over a joist.
What’s required for cantilevered oor joists?
Table 7.2 has the permitted cantilever lengths. Use the 2 kPa (right column) of the table for wet in service situations such as balconies with timber slat decking (saddle ashings will be required).
Cantilevered joists require a boundary joist. Joists need to be laterally supported at the point of cantilever (above the supporting wall) with solid blocking to the depth of the joist.
NZS 3604:2011 does not consider cantilevered joists that support external braced walls. This would require speci c engineering design.
How much can joists be notched and checked?
The maximum check or notch allowed for a joist is 32 mm or the depth of the joist divided by 5, whichever is less. For example, a 140 mm joist could be notched 28 mm. The notching or check- ing can only occur within 450 mm of the support (see Figure 6).
NZS 3604:2011 does not permit notching or checking of bearers.
d/5 or 32 mm (whichever is less)
depth (d)
d minimum d minimum
3 × d maximum for holes in joists
(a) Holes in joist of minimum depth for span.
joist deeper than minimum required from joist span tables
required depth (d)
d/5 or 32 mm (whichever is less)
edge notches 450 mm maximum
d minimum
(b) Notches in joist deeper than minimum required for span.
jois
depth (d)
(c) Notches in joist of minimum depth for span.
centreline of joist
d/5 or 32 mm (whichever is less)
t
d minimum
edge notches 450 mm maximum
Figure 6 Holes and notches in oor joists (redrawn from NZS 3604:2011 Figure 7.8). Build 13519—Decemberr201153//JJanuarry201164 — 33