Compliance Document for
New Zealand Building Code
Clause E2
External Moisture

Handy information about acceptable solutions for larger roof penetrations. As an example larger diameter flues 85mm and above. Flashing methods include soaker flashing.

You will also find information about downpipes and spreaders as follows:

Gutters general
Gutters, downpipes and spreaders, including
eaves gutters/spoutings are required for the
drainage of roof water, and shall:
a) Be to the minimum dimensions shown in
this Acceptable Solution, or calculated to
E1/AS1, whichever is the greater
b) If a gutter depth is reduced to allow entry of
a valley gutter, the reduced depth must be
used to calculate the capacity of the gutter
c) For internal, valley, and hidden gutters,
have no fixings in gutter bottoms or sides,
and be continuously supported on H1.2
minimum treated timber gutter boards or
H3 ply which is separated from metal by
roof underlay strip.
Eaves gutters/spoutings shall:
d) Be to any of the materials outlined for
flashings in Paragraph 4.1 except 4.3.9,
4.3.10 and 4.3.11

... More on this in Acceptable Solution E2/AS1 attached

Linkback: https://www.plumbers.nz/code-downloads/13/e2-external-moisture-effective-acceptable-solution-e2as1/1295/