Reference points
Residential paths and driveways in Australia are covered by AS 3727.1, the standard for residential pavements, with AS 3600 behind concrete strength and AS 2890.1 behind driveway grades. On the strip between boundary and kerb the council's own drawing governs: A1300 in the City of Newcastle, EGSD 201 and 202 in Lake Macquarie. The Section 138 guide sets those out side by side.
Reading the ground
The region changes underfoot within a short drive. Close to the ocean and around the lake edge, slabs sit on sand that drains freely and needs confining at the edges. West of the city the soil turns to reactive clay that swells when wet and shrinks when dry. Estate lots are often benched, cut on one side and filled on the other, and older suburbs hide filled pits, old footings and tree roots. The measure starts with which of these the job is standing on, because the base follows from the answer.
Base and preparation
Topsoil, roots, soft spots and old surfacing come out. The subgrade is trimmed to firm material and a granular base is placed and compacted where the ground calls for it, deeper over weak or reactive ground. A membrane goes under the slab where conditions call for one. Skipped preparation is the most common reason a young slab cracks or rocks, and it is invisible in a finished photo.
Steel
Reinforcing mesh belongs inside the slab, held up on bar chairs, where it can restrain cracking. Mesh laid on the ground and poured over does nothing. Heavier mesh is used where vehicles stand or turn, extra bars go in at re-entrant corners and around pits, and new slabs are dowelled to existing ones where the two must stay level.
Thickness by use
- Paths and clothesline pads: commonly 75 to 100 mm, and 100 mm wherever a vehicle might cross.
- Driveways for cars: commonly 100 mm in 25 MPa concrete with SL72 mesh, thicker with heavier mesh for larger vehicles, caravans and boats.
- Council crossings: the council minimum, 100 mm in Newcastle and 125 mm in Lake Macquarie, both in 25 MPa concrete.
- Patios and alfresco slabs: commonly 100 mm, jointed away from the dwelling.
Shed and garage slabs
The shed supplier's engineering governs. It states slab thickness, mesh, edge thickening and hold-down positions, and the slab is set out to it. Expect thickened edges under the frame, a rebate at roller doors so water drops outside, local thickening under hoists or heavy machinery, and a slight fall on open carports. Slabs for dwellings and granny flats are a separate certified process and are not referred through this site. Worked prices are in the shed slab cost guide, and the service is described under shed and garage slabs.
Paths beside a house
A path against a wall is set below the damp course, falls away from the building and keeps weep holes and vents clear. It is separated from the dwelling with a joint so each can move. Downpipes, pits and taps are formed around, not buried. On reactive clay, paving hard against a house with no fall is a known cause of damp problems, so levels are agreed before the pour.
Joints
All concrete cracks. Joints decide where. Control joints are tooled or saw cut at regular spacing and at changes of shape, early enough to work. Newcastle's crossing drawing sets joints no more than 3 metres apart, and Lake Macquarie asks for a full depth saw cut at the boundary and an expansion joint at the layback. Isolation joints keep new concrete free of walls, footings and old slabs.
Water
Falls are taken from real levels at the measure. Water goes to the street, a pit or a grated drain, never to the garage, the house or the neighbour. On flat, low-lying blocks this is the part of the design that matters most.
Finish and curing
Broom finish for grip, coloured concrete with oxide through the mix, or exposed aggregate washed back to stone. Concrete gains strength over about four weeks: foot traffic is normally fine the next day and most concreters ask for around a week before cars, longer in cold weather. Sealing suits exposed and coloured finishes inside the boundary, but Newcastle does not permit sealer on the council crossing.
Mine subsidence
Large parts of both council areas lie inside declared mine subsidence districts, among them the Newcastle, Lake Macquarie and Killingworth-Wallsend districts. For flat concrete it seldom changes anything: Subsidence Advisory NSW's exempt development list includes driveways and hard stand spaces under all of its guidelines except guidelines 4 and 5. Structures are different, and a garage or large shed may need to meet the guideline for its lot, which can alter the slab. Search the address on the NSW Planning Portal Spatial Viewer before a kit is ordered.
Using this page
Ask each concreter to put thickness, mesh, concrete strength, base preparation, joint layout and drainage in writing, along with who prepares and lodges any council application. Then read the answers against this page, the cost guide and the calculator. Where an old slab is coming out first, see removal and replacement, and for outdoor living areas see patios and alfresco. A lower price nearly always lives below the surface.