What is a Gutter

A Gutter is a narrow channel, or trough designed to collect and transfer rainwater to a suitable drain. 

Gutters collect and diverts rainwater to protect a building's fabric and foundation by channeling water away from a building's base. It also helps to reduce erosion, prevents leaks in subfloor spaces, protects painted surfaces by reducing exposure to water, and provides a means to collect rainwater for later use. 

Typically, it is a discrete trough of metal, or other material that is suspended beyond the roof edge and below the projected slope of the roof.

Rain gutters can be constructed from a variety of materials, including zinc, galvanised steel, painted steel, painted aluminium, plastic, and concrete.

Gutters must be installed with a "fall" so that water flows towards the down-pipe or drain connection. Gutters with inadequate fall will allow water to pond shortening the life of the gutter and creating a condition conducive to timber pest activity.

Different styles of gutter, known as profiles, are produced. A box gutter is a deep gutter which is concealed within the structure of the roof. Cold forming technology exists to allow continuous gutters to be created, on site, in long individual lengths suitable to roof edge conditions, thereby reducing joints along the length of the gutter. These mostly joint free gutters are referred to as "seamless", and available in various shapes, sizes, and finishes
Clogged gutters can cause water leakage into the house as the water backs up as well as encourage mosquitoes to breed.

Guttering should be installed by a licensed roof plumber. Having the correct roof plumbing will ensure that water will flow off the roof correctly in even the heaviest of rainfall, or if there is a water tank, that water catchment is maximised. The roof plumber will take the size, pitch and material of the roof into account when designing the appropriate water catchment or stormwater drainage system and also when selecting the guttering material as certain materials may be incompatible with each other and the roof covering.

According to BCA Vol 1 Part 3.5.2

"The roof drainage system including gutters and downpipes should be connected to a compliant stormwater drainage system and should be designed so that any overflow during heavy rain periods is prevented from flowing back into the building

Gutters, downpipes and flashings must:

• Be manufactured in accordance with AS/NZS 2179.1 for metal
• Be manufactured in accordance with AS 1273 for UPVC components and
• Be compatible with all roofing materials in accordance with BCA Vol 1 3.5.1.3
• Not contain any lead if used as part of a water catchment system.

Mandatory guttering size will vary depending upon the average rainfall intensity and roof catchment area.

Gutters must be installed with a fall of not less than 1:500 for eaves gutters, unless fixed to metal fascias and 1:100 for box gutters.

Eaves gutters must be supported by brackets securely fixed at stop ends and at no more than 1.2m centres.

Valley gutters on a roof with a pitch more than 12.5 degrees must have width of not less than 400mm and be wide enough to allow roof covering to overhang not less than 150mm each side of the gutter or if the roof has a pitch more than 12.5 degrees be designed as a box gutter.

Where high-fronted gutters are installed, provision, provision must be made to avoid any overflow back into the roof by installing slotted gutters or the like.

Downpipes must not serve more than 12m of gutter length for each downpipe and be located as close to possible to valley gutters and if more, provision for overflow must be made to the gutter Downpipes must be selected in accordance with the appropriate eaves gutter section.

Stormwater drainage systems are not designed to remove all of the water during exceptionally heavy rain. Accordingly, it is necessary to design and install the system so that when overflowing occurs any water is directed away in a manner which ensures that it does not pond against or enter the building. This may be achieved by using slotted gutters, oversized gutters and downpipes, locating the gutter so that it is below the top edge of the fascia or the installation of rainwater heads with overflow slots".


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