The usual rule of thumb for an eaves gutter is a 1:500 fall towards the downpipe, or about 2 mm of gutter fall per metre. Treat this as general guidance because the applicable building requirements, gutter system and manufacturer’s specifications may require a different gradient.
What does a 1:500 fall mean?
A 1:500 gradient means a drop of 1 mm over 500 mm of horizontal distance. For example, a 10-metre run would have a nominal fall of 20 mm from its high point to the outlet.
The fall should be continuous. An adequate overall drop does not prevent isolated low spots from holding water. Fall controls flow direction, but it does not establish whether the gutter, outlet and downpipe placement provide enough capacity.
Can the wrong fall cause leaks?
Yes. Backfall or isolated low spots can leave standing water, direct runoff away from the outlet and increase overflow during rain. Persistent ponding can also expose weak joints, end caps and corroded sections. However, blocked outlets and downpipes can create similar symptoms, so the leak source should be confirmed before the gutter is adjusted.
Routine gutter cleaning may reduce blockage-related overflow, but it will not correct poor fall, inadequate capacity or damaged metal.
When might 1:500 not apply?
The required design can depend on:
- the gutter profile and fixing method
- the roof catchment draining to each section
- local design rainfall intensity
- gutter, outlet, downpipe and overflow capacity
- current National Construction Code requirements and manufacturer instructions.
These factors should be checked for the specific property rather than relying on the rule of thumb alone.
Observe gutters from ground level and follow safe gutter inspection limits. Do not access a roof or use an unsecured ladder to measure or adjust gutters. Roof drainage falls and corrections should always be handled by a licensed roof plumber in accordance with AS/NZS 3500.3 (the Australian roof drainage standard, which specifies gutter sizing and minimum slopes to prevent stormwater overflow into eaves, fascia boards, and internal ceilings). If a gutter is holding water, overflowing into fascia boards, or needs re-pitching, contact our licensed leaking gutter plumbers. Fixed Today has supported Sydney homeowners for over 15 years with genuine upfront fixed pricing and clear task breakdowns. Letting us know the approximate building height and whether you have visible overflow marks or leaking corner mitres helps our crew arrive equipped with the right ladders, brackets, and alignment tools.