Deep soil zone

A deep soil zone is contiguous natural ground with no slab or structure beneath it, of a minimum width, required as a percentage of the site so trees can root and stormwater can infiltrate. Under the NSW Apartment Design Guide (ADG), for example, the minimum is around 7% of the site area with minimum dimensions, and similar controls appear in other states’ apartment and landscaping provisions.

The point of the control is real landscaping and drainage, not token greenery. A deep soil zone has to be:

• Contiguous natural ground, connected soil, not scattered garden beds, with a minimum width/dimension so a tree can actually establish.
• Free of structure below, which is the key catch: a planter box on a podium, a garden over a basement slab, or landscaping above any structure does not count as deep soil, because the roots cannot reach natural ground and water cannot infiltrate.

That structure-below rule is where projects trip up: maximising the basement or podium footprint can leave nowhere for a compliant deep soil zone, and the design has to give ground back.

For a builder or designer the practical points are to locate the deep soil zone early and protect it from the basement/podium footprint, because retrofitting it means shrinking the structure below. Confirm the required percentage and minimum dimensions for the controlling instrument (ADG in NSW, the relevant scheme elsewhere), and remember podium and above-slab planters are landscaped area but not deep soil, they are counted separately. Getting this wrong is a common reason an apartment scheme fails to meet its landscaping controls at DA.

Also known as: Deep soil area, deep soil planting.

Category: Planning / Landscaping.

Related

• Landscaped area and deep soil

See also

• Site area calculation

References

• Landscaped area and deep soil (Chalkline) (verified 2026-06-03)

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Last updated: 2026-06-03. Verified: 2026-06-03. Quarterly review for currency.