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Concrete Thickness for Sidewalks: Selecting the perfect thickness

Scooters, bikes, skateboards, or even rollerblades all glide along smooth concrete sidewalks. Sidewalks chart paths all over the world that connect society together, and while it does take a lot of concrete you would be surprised to see the attributes and thickness that make up such a well-used path.

The best thickness for concrete sidewalks is 4 inches for walkways and 6 inches if cars will be driving across it, such as a sidewalk in front of a driveway. A sidewalk must be thick enough to bear the projected load. A sidewalk that is too thin can crack and erode under pressure.

When building or making walkways, concrete has become incredibly popular. This is probably due to the fact that “concrete is readily available in most areas and requires less specialized equipment than asphalt and less labor than brick pavers. ” Source. Therefore, while sidewalks are already here, they will continue being poured.

Not Thick Enough VS Too Thick

It seems there is a toss-up in the concrete world between the cost and the durability of concrete. As previously stated, concrete must be 4 inches thick for a sidewalk, but what happens if it is not that thick? Or what if it far exceeds those 4 inches? One can only imagine the results of thin concrete.

Thinner concrete changes with the surrounding temperature much more quickly than thicker concrete does. The results would be cracking under too much pressure and deteriorating much more quickly.

Stronger concrete doesn’t yield quite the bad results that thin concrete does. “Concrete is stronger when it’s thicker, but resources are wasted if the thickness exceeds what’s necessary for the structure’s performance”. Source

Yet another aspect to consider is consistency. Imagine a sidewalk that was falling apart in some places, and bulging in others. It doesn’t seem to please the eye. When pouring concrete, it is important to make sure that it is even.

The only difference between the line of flattened earth and soil and the line of concrete should be the thickness of it. Sidewalks follow the level of the earth. “Soil is part of the support system for concrete structures; the weight that is bearing on the concrete is transferred to the soil. The subgrade has to give uniform support to the concrete, or it may bend, causing it to crack.” Source. Below is a little more about the subgrade, or base layer.

Having A Base

Laying siding can also be tricky as you consider the foundation where your sidewalk will sit. Usually, before the concrete ever makes its way into the process, a base of gravel is laid. The base is usually four to eight inches thick and must be even and packed down before you begin pouring.

Another important point to consider as you lay concrete is to never lay the mixture directly onto grass or sod. The reason for this is “the organic plant material decays and causes the base to settle, which can lead to cracks in the sidewalk.” Source

Reinforcing Sidewalks

Additional reinforcement can be made to improve the life, appearance, and durability of your concrete. While most sidewalks do not require the extra support given through reinforcing it, it can be helpful in holding the sidewalk together when it does crack.

At one point, we each see a sidewalk that is not only cracked but jetting into the air at every crack and creating the perfect place to trip and fall. This happens over periods of time if the concrete is not reinforced.

If you do want to reinforce concrete, you can use rebar, wire mesh, or steel. For only 4 inches of concrete, wire mesh is suggested. You can do this by first laying down slab runners in order to hold your mesh off your base, positioning it in the middle of your concrete’s thickness. Additional instructions can be found here.

Exceptions – Other Thickness Needs

By taking into account the weight of the load each slab of concrete must bear will help in determining how thick your concrete needs to be. Four inches for a normal, standard sidewalk, or for a small driveway that will only hold small vehicles. In essence, the more the weight the thicker it should become.

If a sidewalk crosses a driveway or other space where larger vehicles will be crossing, it is suggested to increase the thickness of your concrete to six or eight inches. Below are some other examples that may help put into perspective the thickness you need:

  • Parking lots are generally 6 inches thick.
  • Loading docks or dumpsters pads may be as thick as 12 inches.
  • Commercial driveways are normally 8 inches thick.
  • Highways are standardized from 11 to 12 inches thick, but this can change dependent upon the amount of traffic.

Other Facts

When it comes down to laying a sidewalk, and determining the thickness needed for walkways and other transportation pathways, much has to do with the earth and soil underneath, the temperatures it will be subject too, and the weight your planning to have upon it. Here are some short facts that might also be helpful.

  • “A slab that is too thick is a waste of the customer’s money, but one that is too thin will lead to premature collapse.” Source
  • Adding even 1 more inch to your 4-inch sidewalk can increase the load-bearing capacity by nearly 50 percent.
  • While your thickness should be uniform, slanting the sidewalk ever so slightly away from a nearby home or building will allow drainage not to build up around it.
  • Driveways typically hold 1,800 psi to 4,000 psi (pounds per square inch).
  • Additional strength can be found in concrete by using a stronger cement powder.

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