How to lay pavers in Australia and New Zealand

1. Plan the levels first

Before you dig, decide where the water will go. Paving that falls towards a house sends every storm at the slab and the brickwork. The Australian building code, NCC 2022 Housing Provisions 3.3.3, asks for the ground around a slab to fall at least 50 mm over the first metre. Paving in low-rainfall areas may fall 25 mm. The slab itself must sit at least 50 mm above paving that slopes away. For brick walls, Part 5.7 asks for the damp-proof course to be 75 mm above paving in most situations, with lower figures under a verandah or in low-rainfall areas. Weep holes must stay clear.

In New Zealand, BRANZ recommends a fall of 1:25 away from the building. E2/AS1 asks for the floor level to be at least 100 mm above paving for brick veneer and 150 mm for other claddings. Paver makers on both sides of the Tasman ask for around 25 mm of fall per metre (1:40) on open paving, so rain runs off rather than ponding.

Run string lines at the finished paving height, with the fall built in, before you dig anything. Everything else is measured down from those strings.

2. Dig to the right depth

Excavation depth is the sum of the layers:

Dig slightly wider than the paving so the edge restraint has something to sit on. Firth allows an extra 150–170 mm each side for a concrete haunch. Take out all topsoil and roots. Organic material rots and leaves hollows.

3. Build and compact the base

The base is crushed rock: road base, DGB20 or crushed recycled concrete in Australia, GAP20 or GAP40 in New Zealand. Depths in the laying guides range from 50 mm (Austral, and NZS 3116 on average soil) to 100–150 mm (National Masonry). New Zealand's paving standard, NZS 3116, ties the depth to soil strength. On firm ground a patio may need no separate base at all, and on weak soil a driveway needs 100 mm.

Lay it in layers no thicker than about 50 mm, dampen it, and compact each layer with a plate compactor. National Masonry asks for road base compacted in 2–3 layers, and Adbri says to compact at least three times. Build the fall into the base, not into the sand. The paver calculator converts the depth into tonnes. Order by weight: compacted road base weighs about 2.2 t/m³, while a loose load weighs 1.9–2.1 t/m³.

4. Edge restraints before pavers

Unrestrained pavers creep outwards, joints open and the whole area loosens. Every guide asks for a fixed edge on every open side, built before the pavers are compacted. Use a concrete haunch (Adbri suggests a 4:1 sand and cement mix), a mortared row of pavers, or a proprietary edge strip. Firth wants the restraint to go at least 50 mm below the bedding sand. For driveways, National Masonry calls a concrete edge "essential".

5. Screed the bedding sand

The bedding layer is 25–30 mm of washed, coarse river sand, screeded flat and not compacted until the pavers are on it. National Masonry notes that it compacts by about 10 mm. Keep it thin. The Concrete Masonry Association of Australia warns that beds thicker than about 30 mm compact unevenly. The bedding sand is not for fixing levels, so any dip in the base will show through the paving.

On an existing concrete slab, pavers can be laid on mortar or adhesive instead. Adbri then allows tight joints but asks for expansion joints at least every 4 m, lined up with the slab's control joints.

6. Lay, cut and space

• Start from a straight, fixed edge, usually the house or a restraint, and work forwards so you kneel on laid pavers, not the screeded sand.
• Joints. 2–3 mm for small pavers, 4–6 mm for large formats of 300 × 300 mm and up (Austral). Pavers with spacer nibs set their own gap.
• Pattern. Herringbone interlocks, which is why the CMAA specifies it for driveways that carry heavier vehicles. It also needs more cuts at the edges, as do curves.
• Cuts. Use a masonry saw or a paver guillotine. Manufacturers suggest ordering 2–10 % extra depending on the layout: Adbri says 2 %, the Australian Paving Centre 5 %, and National Masonry up to 10 %. The paver calculator lets you choose.

7. Compact and fill the joints

Run a plate compactor over the pavers with a rubber mat or carpet under the plate. Dricon specifies a 60–120 kg plate, at least two passes before jointing and two after. National Masonry says to use a mallet and a plank instead for pavers thinner than 50 mm. Firth says not to plate-compact 400 × 400 mm pavers at all, only a rubber mallet.

Sweep dry jointing sand into the joints until they are full, compact again, and top up. For 200 × 100 × 50 mm pavers with 3 mm joints that is about 3.3 kg per m², and for 400 × 400 × 50 mm about 1.1 kg per m². Polymeric or "stabilised" jointing sand sets and resists weeds and ants. It only suits narrow 2–4 mm joints, needs about three dry days, and should not be used around pools or on steep slopes.

8. Driveways are different

A car puts far more load through a paver than foot traffic. The CMAA recommends 60 mm pavers for light vehicles and 80 mm, laid in herringbone, for heavier traffic. Pavers 40 mm or thinner are for pedestrian areas only. Bases go up to 100–150 mm of well-compacted crushed rock, or a concrete slab. A concrete edge restraint is essential. On reactive clay or anywhere water lies, get a design.

9. Mistakes that make pavers sink

1. Fixing levels in the sand. A thick patch of bedding compacts more than a thin one, and the paving dips there within months.
2. Too little base on soft ground. Clay and fill move when wet. Go deeper, or put a slab under the pavers.
3. No edge restraint, or one added after compaction. The edges spread and the joints open.
4. Crusher dust or cement in the bed or joints. Stains, efflorescence and cracking.
5. Not enough fall, or falling towards the house. Ponding, slippery moss and water under the slab.
6. Paving over the damp course or weep holes. A building defect as well as a moisture problem.

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