How to Form Up Timber Shuttering for a DIY Concrete Driveway

Setting up timber shuttering (also called formwork) is one of the most important steps in laying a concrete driveway — get it right and the rest of the job flows smoothly. Done well, your shuttering acts as a mould that holds wet concrete in shape, controls the finished level, and gives you a straight, even slab that drains correctly.

What Timber Should You Use?

For most residential driveways, 25 mm × 150 mm (1" × 6") rough-sawn timber is the standard choice. It's stiff enough to hold concrete without bowing, easy to stake, and widely available at Bunnings, Mitre 10, or PlaceMakers. For a thicker slab (say 100 mm or more), use 200 mm-wide boards so the form face covers the full slab depth.

• Choose straight, knot-free boards where possible — bowed timber creates wavy edges.
• Avoid treated timber that has been freshly dipped, as some treatments can affect concrete curing. H3 treated pine that has been allowed to dry is generally fine.
• Hardwood (e.g. macrocarpa) is more rigid and reusable but costs more.

Planning the Layout and Falls

Before you drive a single peg, spend time on planning. A concrete driveway must shed water away from the house and towards a legal stormwater outlet — this is a requirement under NZ Building Code clause E1 (Surface Water). A minimum cross-fall of 1:100 (1 cm per metre) is generally recommended, though 1:50 is more practical for driveways to ensure good drainage.

1. Mark out the driveway edges with a string line and pegs.
2. Establish your datum level — usually the existing garage floor or kerb channel — and work backwards from there.
3. Use a builder's level or laser level to transfer heights to your form boards. A water level works well for longer runs.
4. Check with your local council whether a building consent is required. Many residential driveways fall under Schedule 1 exemptions, but this depends on size, proximity to boundaries, and whether stormwater connections are involved — always confirm with your council before starting.

Setting the Stakes

Timber pegs (typically 50 × 50 mm or 38 × 38 mm) are driven into the ground on the outside of the form boards at 600–900 mm centres — closer together on curves or soft ground.

• Drive pegs so their tops sit at or just below the top of the form board (so a screed bar can pass over cleanly).
• Use double-headed (duplex) nails or screws to fix the board to the peg — these are easy to remove after the concrete sets.
• Check the board is plumb (vertical face) so the slab edge is neat.
• On longer runs, join boards with a peg at the joint, overlapping slightly or butting tightly.

Achieving Curves and Corners

For curved edges (e.g. a flared entrance), kerf-cut the form board on the back face at regular intervals (every 50–100 mm depending on the radius) so it bends without splitting. Alternatively, use flexible hardboard or ply for tight curves. Secure extra pegs on curves to prevent the board springing outward under concrete pressure.

For right-angle corners, mitre or butt the boards and double-peg the junction.

Checking Levels Before You Pour

Once all boards are in place:

• Run a string line across the top of both form boards and check the cross-fall with a level and tape measure.
• Sight down the length of each board — any bow or twist needs correcting now.
• Confirm the slab thickness by measuring from the top of the form down to your prepared sub-base. For a standard residential driveway, 100 mm is typical; driveways used by heavy vehicles may need 125–150 mm (seek engineering advice for these).
• Compact your sub-base (GAP 20 or similar) thoroughly before pouring — a poorly compacted base is a leading cause of cracked driveways.

Releasing and Removing the Formwork

Lightly coat the inside face of the boards with form release agent, or a suitable mould-release product before pouring — this stops concrete bonding to the timber and makes stripping much easier. Remove the forms 24–48 hours after pouring once the concrete has hardened enough to hold its shape, but avoid leaving them on for weeks as they can cause uneven moisture loss.

Expansion and Control Joints

Don't forget to plan for control joints (also called contraction joints) at roughly 3–4 metre intervals along the slab length. These can be formed with a grooving tool while the concrete is still green, or by inserting temporary timber strips (later removed) into the pour. Without them, random cracking is almost inevitable. For more technical guidance on concrete slab construction, BRANZ is an excellent NZ resource.

When to Call a Professional

While forming shuttering is a manageable DIY task, there are situations where a qualified driveway layer or concretor is the smarter choice:

• Sloping sites with significant cut-and-fill, retaining requirements, or drainage complexity.
• Large or commercial driveways where engineering input may be required.
• Stormwater connections — connecting to the council stormwater network is typically restricted work requiring a licensed drainlayer (see the Plumbers Gasfitters & Drainlayers Board).
• If you're unsure about consent requirements, a professional will know what's needed in your area.

You can find experienced local driveway layers and concretors on tradedirectory.co.nz — always ask for references and check they carry public liability insurance.

Sources & Further Reading

• BRANZ – Concrete Slabs and Driveways
• MBIE Building Performance – Building Consent Exemptions
• Bunnings – Concrete and Formwork Supplies
• Mitre 10 – Timber and Building Products
• PlaceMakers – Concrete and Formwork Timber
• WorkSafe NZ – Safe Work on Construction Sites