Page 38 - Build 152

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10 October 2011
DEPARTMENT OF BUILDING AND HOUSING
Amend 1 Sep 1993
90 200 40 35 70 60 80 65 105 90
Amend 2 Aug 1994
than that required by Table 5, and they passage of a 50 mm diameter sphere.
intensity “I”
exceeds 100 mm/hr the required gutter size shall be increased by taking the value read from the figures and multiplying it by the ratio of “I”/100. Paragraph 3.2.2 describes how to determine the value of “I”.
Table Downpipe Sizes for Given Roof Pitch and Area 5: Paragraph 4.2.1
Downpipe size (mm)
Roof pitch
Plan area of roof served by the downpipe (m2)
(minimum internal sizes)
0-25° 25-35°
35-45°
45-55°
63 mm diameter
74 mm diameter 100 mm diameter 150 mm diameter 65 x 50 rectangular 100 x 50 rectangular 75 x 75 rectangular 100 x 75 rectangular
60 50
40 35 60 50
85 70 155 130 350 290
110 250
60 50 100 80 110 90 150 120
Amend 2 Aug 1994
Amend 1 Sep 1993
Figure 2 New Zealand Building Code clause E1 Table 5.
Acceptable Solution E1/AS1
SURFACE WATER
Figure 15:
Cross-sectional Area of External Gutter
Figure 16:
Cross-sectional Area of Internal Gutter
Paragraphs 5.1.2 and 5.1.3
Paragraphs 5.1.2 and 5.1.3
Amend 1 Sep 1993
Figure 3 New Zealand Building Code clause E1 Figure 15.
Gutters will be the same size for all the roof so use the largest plan area to work out the appropriate size gutter. The largest plan area is area A at 38 m2.
This is an external gutter, so using clause E1 Figure 15, plot 38–40 m2 plan area on the vertical axis. Then read o the gutter size for the roof pitch of 45° (see Figure 3).
In this case, the cross-sectional area of a section of gutter is approximately 7,000–8,000 mm2, so a 125 × 70 mm gutter (8,750 mm2) will meet the requirements of E1.
36 — February/March 2016 — Build 152