A little knowledge goes a long way in helping you make an educated decision when hiring a contractor. If you are looking at having a new concrete driveway poured, you may be asked to decide if you’d like wire mesh or rebar used for support. If you have no idea how to answer that question, this article will provide a brief overview to give you an informed decision.
Wire mesh is made from cold reduced deformed steel. It comes to the contractor in a roll that, when laid out, is a series of open squares. Imagine square chicken wire made of thick steel bars. The bars have ridges to help the concrete attach to them. The wire mesh is used to add strength to the concrete. First, it is there to give support during the “green” period when the concrete is setting. Then it helps maintain the concrete’s integrity against cracking during its lifetime.
Rebar, shortened from “reinforcing bar,” is also made of steel. It is rounded bars with ridges that measure in sizes varying by 1/8th inch thickness. Also used for support, rebar is generally laid individually in larger squares than the wire mesh. Rebar is a major component in adding strength and maintaining structure when cracking occurs.
So which do you chose?
Wire mesh is cheaper than rebar. Firstly, wire mesh is made of thinner steel bars, so less materials. As you’ll recall, it can be rolled up. And secondly, because it does come in a roll, the labor of installation is less intensive. Rebar’s cost will depend upon the thickness of the bars and will ultimately add to more labor expense.
Rebar is definitely the stronger candidate for support. However, that said, if we’re talking about a four inch thick residential driveway (four inches is the thickness recommended for driveways holding less than 10,000 lbs), mesh does the trick just fine. In fact, many contractors consider rebar for residential jobs overkill. If you are looking to get a thicker driveway because you plan on having heavy trucks or an RV parked on it, then rebar is a good suggestion.
Both wire mesh and rebar cannot prevent cracking, but are helpful in holding the concrete together when cracking occurs. The steel behaves similarly to concrete in how it expands and contracts during hot and cold temperatures, which is why it’s used in concrete slabs. Likewise, the mesh and rebar will stop small cracks from expanding further. Wire mesh must be laid correctly to serve the concrete best. It should be directly in the middle of the slab. So a four inch slab should have the wire mesh two inches deep. If it becomes exposed to the air, it ultimately can rust and lead to cracking. But a good contractor will make sure that doesn’t happen. Some contractors feel the smaller squares of the mesh, and the thinner steel, allows for more flexibility as the contractions in the concrete occur, staving off cracking better than rebar.
The myth about strength
When people talk about mesh or rebar and compare it for strength, one major part of the discussion should focus on the base of the concrete slab. Neither wire mesh nor rebar will perform its duty if the bottom of the slab isn’t laid properly to hold concrete.