Wire Mesh vs Rebar for a Concrete Driveway

For a concrete driveway that's going to be reinforced, 10M rebar on chairs usually does a better job than wire mesh, because it's easier to keep at the right depth and it puts more steel in the slab. Light 6x6 mesh is quicker to roll out, but it often ends up trampled to the bottom of the slab, where it does very little. That said, reinforcement is not what makes a driveway last in Ontario. The right concrete, a well-compacted base, control joints at the right spacing and proper curing do most of the work, and many good driveways are plain concrete.

What reinforcement does in a driveway, and what it doesn't

All concrete shrinks as it cures and dries, and a driveway slab on the ground is restrained by its base, so it cracks. Control joints tell it where to crack. Steel reinforcement:

• Holds cracks tight once they form, so the panels on each side stay level and water and salt get in less.
• Ties pieces together if the slab cracks through or the base settles a little.
• Does not prevent cracking, doesn't replace joints, and can't fix a soft or poorly compacted base.

That last point is the most important. A driveway on a soft, wet or uncompacted base will crack and settle with or without steel. Concrete Ontario's reference guide for exterior flatwork stresses subgrade preparation, the right concrete, joints and curing, with no mention of reinforcement as a fix for any of them.

Wire mesh vs rebar side by side

The steel areas come from Concrete Ontario's reference guide, which lists 152x152 MW9.1 x MW9.1 at 59.9 mm² per metre and 152x152 MW18.7 x MW18.7 at 124.5 mm² per metre. A 10M bar is 100 mm², so at 400 mm spacing it gives 250 mm² per metre each way. Even heavy 6x6 mesh adds about half the steel of 10M at 400 mm.

Mesh names can be confusing. The metric designation 152x152 MW18.7 x MW18.7 means wires 152 mm apart each way with a cross-section of 18.7 mm². Its imperial equivalent is 6x6 W2.9xW2.9, still often sold as "6x6 6/6" from the old gauge numbers. For a fuller comparison on all slab types, see wire mesh vs rebar vs fibre for concrete slabs.

The real problem with mesh: where it ends up

Steel only helps if it's in the slab where the cracks are. Shrinkage cracks start at the top surface, so reinforcement in a slab on grade is generally placed in the middle to upper part of the slab, with enough concrete over it to protect it.

Mesh delivered in rolls tends to sit flat on the base. The common fix, pulling it up with a hook during the pour, is unreliable, and workers walking on light mesh push it back down. Mesh on the bottom of a driveway is doing almost nothing.

Concrete Ontario's guide recommends supports at 0.8 m or less for light mesh (wire sizes MW25.8 and smaller), which is most driveway mesh. Rebar is stiffer, so chairs can be further apart, and it holds its position better while concrete is placed. Either way, the steel must sit on chairs or bolsters, not on the ground.

Salt is the other reason position matters in Ontario. Steel that ends up too close to the top surface of a driveway exposed to de-icing salt can corrode and spall the concrete above it. Our post on concrete cover for rebar explains how cover is set.

What size rebar for a driveway?

When a residential driveway is reinforced in Canada, 10M is the usual bar. It's 11.3 mm in diameter (close to a US #3 or #4), the smallest Canadian metric size, and it fits in a typical driveway slab with room for cover above and below. 15M bar shows up on heavier slabs, such as those carrying trucks or equipment, and on engineered aprons. For how the two compare, see 10M vs 15M rebar for a slab.

Spacing should come from your contractor's or designer's specification. It's written as a callout such as "10M @ 400 EW", meaning 10M bars at 400 mm centres each way. Whatever the spacing:

• Keep bars back from the edges so they're covered on all sides.
• Stop or cut steel at control joints if your designer wants the joints free to open, or carry it through if they want the panels tied together. That's a design decision, so follow the drawing or specification.
• Add dowels where the driveway meets a garage slab or existing concrete, if specified.

What actually makes an Ontario driveway last

Concrete Ontario's ten steps for durable exterior flatwork, and the Ontario Building Code, put the emphasis on the concrete and the workmanship:

• The right concrete. Article 9.3.1.6 of the 2024 OBC sets a minimum 28-day strength of 32 MPa for exterior flatwork and garage floors, and Article 9.3.1.7 limits the water to cementing materials ratio to 0.45. Site-batched concrete for exterior flatwork needs 5 to 8% air entrainment for freeze-thaw resistance. Ready-mix for driveways is ordered to suit.
• A well-prepared base. The subgrade must be properly graded and compacted to give the slab uniform support.
• Control joints. Concrete Ontario's guide recommends joint spacing of 24 to 36 times the slab thickness, to a maximum of 4.5 m, cut at least one quarter of the slab depth, with panels as square as possible and joints at re-entrant corners. Saw cuts are made as soon as the concrete can be cut without ravelling, typically 4 to 12 hours after placing.
• Finishing. No finishing while bleed water is on the surface, a broom texture for traction, and no steel trowelling on air-entrained exterior concrete.
• Curing. At least 7 days of curing on exposed concrete, and time to dry before the first salt.
• Timing. Concrete placed late in the fall has little time to cure and dry before freeze-thaw cycles begin.

If the boulevard portion of your driveway (between the sidewalk and street) is being replaced, your municipality may have its own specification and permit for that part. Check before work starts.

So which should you use?

• Plain concrete with good joints is a sound choice for a typical residential driveway on a good base.
• Rebar on chairs is the better reinforcement choice if you want the panels tied together, the base is less certain, or heavier vehicles will use it.
• Mesh is acceptable only if it's properly supported at the right height for the whole pour. If that isn't going to happen, it's mostly wasted material.

On cost, mesh is often cheaper to buy and place, but compare the amount of steel and the placing method, not just the material line. Our post on wire mesh vs rebar cost covers how to compare quotes.

Ordering rebar for a driveway

If your driveway or apron calls for rebar, send us the dimensions and the specified bar size and spacing and we'll quote it, cut to length so your crew isn't cutting stock on site. See our rebar products for straight bar, dowels and fabricated shapes.