Common Drainage Problems in Sydney Backyards

Drainage is the least glamorous part of a landscape and the reason for most of the remedial work we are called to do. Sydney's mix of reactive clay, sandstone shelf and heavily built-out blocks means water has fewer places to go than it did fifty years ago - and it will find the cheapest path, usually towards the house.

1. Falls that run the wrong way

Paving and lawn laid flat, or falling back towards the building, is the most common fault we find. Hard surfaces need a consistent fall - typically 1 to 2 per cent - to a drain or garden bed away from the house. Correcting it usually means lifting and relaying, which is why levels are set at design stage.

2. Nowhere for subsurface water to go

Clay-heavy soil holds water below the surface long after rain stops. The result is a lawn that stays spongy for days, plants that rot at the root, and paving that moves seasonally. The fix is a subsurface ag line network, wrapped and bedded in aggregate, discharging into the stormwater system.

3. Water trapped behind walls and raised beds

Any structure holding back soil needs drainage behind it. Where it is missing, hydrostatic pressure builds through wet seasons and pushes the wall forward - and the garden bed above stays saturated. Weep holes alone are not drainage.

4. Overland flow from neighbouring properties

On sloping Sydney blocks, upslope neighbours discharge across your land whether either of you intended it or not. Managing that legally and physically - swales, intercepting drains, connections to the legal point of discharge - has to be resolved with council rules in mind, not just a shovel.

• Standing water 24 hours after rain - subsurface drainage failure
• Efflorescence or damp on the lower brickwork - surface falls towards the house
• A retaining wall leaning forward or cracking - no drainage layer behind it
• Moss, algae and consistently bare patches - chronic saturation and shade
• Silt fanning across paving after storms - uncontrolled overland flow

We have never regretted spending money on drainage. We have often been called back to fix the gardens where somebody else saved it.

How we deal with it

Every project starts with a level survey and a drainage strategy: where water arrives, where it goes, and how it gets there. Ag lines, pits, linear drains, permeable surfaces and planted swales all get documented and installed before paving. It is buried work nobody ever sees, and it is the reason the visible work survives.