Paving next to your house: fall, drainage and slab height explained

Short answer: paving next to a house should fall away from the building, at a minimum of 50 mm over the first metre in the general case, and it should sit far enough below the slab that water cannot reach the walls. The National Construction Code's housing provisions require the slab to sit at least 150 mm above the finished ground in the general case, or at least 50 mm above paving or concrete that slopes away from the building as required (ABCB Housing Provisions, Part 3.3.3). Paving that is too high, or falls toward the house, is a common reason for damp walls and wet slab edges.

In South Australia, NCC 2022 (Amendment 2) remains the Building Code until 30 April 2027, with NCC 2025 adopted from 1 May 2027 (PlanSA, state updates). The figures below are from the current SA edition.

The two numbers that matter

1. Fall away from the house

Part 3.3.3(a) of the housing provisions says the finished surface around a slab-on-ground home must be drained to move surface water away from the building, graded to a slope of not less than:

• 50 mm over the first 1 m from the building in the general case
• 25 mm over the first 1 m for reasonably impermeable surfaces (such as paving) in low rainfall intensity areas, and for impermeable surfaces that form part of an access path or ramp

In practice, 50 mm over a metre is about a 1 in 20 slope. You will not notice it underfoot, but water will run off rather than pond.

2. Height of the slab above the paving

Part 3.3.3(b) sets the minimum height of the slab above the external finished surface:

Source: NCC 2022 ABCB Housing Provisions, Part 3.3 Drainage, checked 5 October 2026.

So paving can sit closer to the slab than lawn or garden can, but only if it is laid with the required fall away from the house. Paving built up to the level of the slab, or over the weep holes in a brick wall, defeats the point.

Why it matters on Adelaide clay

Much of Adelaide and the northern suburbs sits on reactive clay that swells when wet and shrinks when dry. When water collects against one side of a house, that side of the footing gets wetter than the rest, and uneven ground movement is what cracks walls and lifts paving. Adelaide University research published on 9 September 2026 found shrinkage cracks in these soils can extend more than a metre deep and carry water much further into the ground. Keeping run-off moving away from the house is cheap insurance.

Signs your paving is draining the wrong way

• Puddles that sit against the wall or the slab edge after rain
• Damp patches, salt marks or peeling paint low on the walls
• The paving surface is level with, or above, the slab or the bottom row of weep holes
• Water runs toward the house from the yard, or into a corner with no drain
• Pavers sinking along the edge of the house (see why pavers sink and how relaying works)

How the fix usually works

One enquiry we had recently is typical: about 45 square metres to repave with proper drainage and fall, dug down around 30 cm, because the existing surface sat high enough that the slab edge was staying wet. The steps for a job like that are:

1. Check the levels. Measure the slab height and the fall across the whole area, and find where the water can go: a stormwater pit, the street or a lower part of the yard.
2. Lift and dig down. Remove the old paving and excavate to a level that gives the required clearance below the slab.
3. Build the base to fall. Compact the base in layers and screed the bedding so the finished surface falls away from the house.
4. Add drainage where fall is not enough. On flat sites or where the yard falls toward the house, a grated channel drain catches water before it reaches the wall and carries it to stormwater. Connections into the stormwater system are plumbing work.
5. Relay and finish. Relay, compact and sand the joints, keeping the paving clear of weep holes and vents.

Do not forget termite protection

Many slab homes use part of the slab edge as part of their termite management system. Under Part 3.4 of the housing provisions, a durable notice is fixed to the home in a prominent spot, such as the meter box, stating the termite management system used and the recommended inspections (ABCB Housing Provisions, Part 3.4). Check that notice before any paving goes up against the house, so the new paving does not cover something that is meant to stay visible.

Getting it right first time

Fall and drainage matter on every paving job, from a patio or alfresco area to a driveway or pool surround. If you are in Gawler, the northern suburbs or the Barossa and water is sitting where it should not, send us a few photos and we will come and check the levels.