Start at the highest point with the back of the gutter
as high as it will go (up against the bottom of the slate
or tile or galvanised iron roof).
Slope the gutter down form there towards the spout.
If the run is long, you may need flashing to cover the exposed
part of the facia. Water will blow in there, and rot the timber
Flashing will start from underneath the roof and bend down and
overlap the back of the gutter.
Don't assume that the gutter is already sloping to the spout.
Check it, get the slope right before installing brackets etc.
Use a transparent plastic hose filled with water to check
Some modern guttering has the back lower at the back than the
Don't use it.
When the gutter overflows, where do you think that the water
will flow? Back to the house, and depending on the design of
the house, water will find its way inside the exterior wall.
If it doesn't do that, it time it will rot the facia.
In some modern houses in Sydney, overflow water found its way
inside the exterior wall, rotting the timbers supporting
the interior wall, floor timbers, and carpets.