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PLUMBING CONNECTION
SUMMER 2015
BOX GUTTERS AND OVERFLOWS
I
n my last article I discussed the emergence of the issue
of provision for overflow in external eaves gutters or
more specifically, the lack of provision for overflow.
This has become a big issue in the past few months,
particularly in Victoria, and is going to be a new section
in the upcoming update to the NCC (See what is currently
stated in Table 3.5.2.3). This is despite the fact that the
Victorian Building Authority (VBA) claims it doesn’t use
the BCA code as it believes their regulations are far more
thorough and make construction in Victoria of a better
standard for the end customer.
As I stated in the previous article, this is not a new
addition to the Australian Standards as it has been included
for over 15 years. What is new is the strong arm approach
the VBA have used to inforce the rectification. VBA has since
agreed it could have been handled better.
The authoritative bodies need to learn from the mistakes
made by the VBA and work on education first. They need to
educate builders, rollformers, roofing companies and even
home owners as to “why” this is necessary.
PETER COLL
PROVIDES A TIMELY UPDATE REGARDING THE PROVISION FOR OVERFLOW AND BOX GUTTER COMPLIANCE.
METAL ROOFING 101
PETER COLL
(DIAGRAM A)
EAVES GUTTER WITH LOW FRONT
Eaves gutter
Fascia
h
f
(DIAGRAM D)
CONCEALED EAVES GUTTER WITH TAIL
Tail
Concealed
eaves gutter
Fascia
h
f
(DIAGRAM B)
EAVES GUTTER WITH HIGH FRONT AND REAR FLASHING
Eaves gutter
Fascia
No seal
required
Flashing
h
f
30mm min.
(DIAGRAM C)
EAVES GUTTER WITH HIGH FRONT AND MIN. 10MM GAP TO FASCIA
Eaves gutter
Fascia
10mm min.
h
f
TABLE 3.5.2.3 ACCEPTABLE OVERFLOWMEASURES
Table a. Acceptable continuous overflow measure
Description
Overflow
Capacity (L/s/m)
Construction
Front face slotted gutter
with -
(a) a minimum slot
opening area of 1200mm
2
per metre of gutter and
(b) the lower edge of the
slots installed a minimum
of 25mm below the top of
the fascia.
0.5
In the previous article I mentioned that this regulation
superseded an older clause in
AS 2180 – 1986 Metal Rainwater
goods – Selection and Installation section 2. Installation, 2.1.2
High-fronted eaves gutters. Where high-fronted eaves gutters
are installed, care shall be taken to ensure that water will not
flow back into the roof or building structure.
Top of fascia