5 Mistakes to Avoid When Pouring a Concrete Slab - Today's Homeowner (2024)

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5 Mistakes to Avoid When Pouring a Concrete Slab - Today's Homeowner? ›

The disadvantages include that heating and cooling units may have to be installed on the ground floor, which takes up living space. There is also a potential for cracks.

The disadvantages include that heating and cooling units may have to be installed on the ground floor, which takes up living space. There is also a potential for cracks.

A base of gravel will help prevent erosion and keep the slab from settling. Pour concrete sand to fill the gaps in the gravel base. Use a tamper or plate compactor to flatten the gravel base. If needed, add more gravel and compact until you have a 4-inch base.

A 2-inch concrete thickness is generally not sufficient for a driveway that will be subjected to regular vehicle traffic.

Cracks. One of the most prevalent issues with concrete is cracking. Understanding the different types of cracks can help identify their underlying causes and determine appropriate repair methods. Plastic Shrinkage Cracks: These cracks occur during the curing process when rapid moisture loss causes the surface to shrink ...

Perhaps the most tell-tale sign of shoddy concrete pouring is the presence of cracks. The primary cause of cracks in dried concrete is tensile stress on the structure.

Built directly on the ground, there is no space under slab foundations for wires, pipes or storage. Often, water and gas lines are embedded into the slab foundation, which can increase costs if you need to access those lines.

If not addressed properly, the moisture vapor trapped in the slab beneath the flooring can liquefy at the slightest change in temperature, which in turn can lead to a host of problems, such as the deterioration of the adhesive, breakdown of the concrete moisture barrier system, and total flooring failure.

Standard concrete floor slab thickness in residential construction is 4 inches.

What happens if you don't put gravel under concrete? ›

What happens if you don't put gravel under concrete? If you don't put gravel under concrete, the concrete can crack, sink, bow, or crumble.

If you use stone, you can typically avoid compacting in place, as it is considered a self-compacting material. If you use gravel, you will need to compact in lifts of 8 to 12 inches. An alternative is to use a cementitious product such as flowable fill.

For slabs thicker than 5 inches, a rebar web is required to prevent cracking. Those that may support structures built on their perimeter or within it should also be strengthened. Reinforce slabs span weak or disturbed ground or run over drainage pipes or ditches.

Sometimes we see settlement cracks simply from poor soil compaction, but this is not as common. Settlement cracks can be prevented by placing thicker concrete in areas that will experience heavier traffic.

A 4-inch-thick concrete slab can support around 4,000 pounds per square foot if a contractor reinforces the slab with rebar, while that same slab without reinforcements will support closer to 1,000 pounds.

Rebar is recommended for concrete slabs that measure 5 – 6 inches in depth, which is about the depth of slab you'd need if you plan to drive on it or use it to house heavy machinery (like a large RV, for example).

Cracks and Fractures

These fissures can manifest as hairline cracks, spiderweb patterns, or large fractures, indicating potential problems within the concrete structure. Settling caused by soil movement or inadequate compaction during construction leads to crack formation as concrete adjusts.

Type V cement is used in concrete products where extreme sulfate resistance is necessary. Coastal structures, piers, underwater tunnels, submerged structures, foundations, roadways and transportation products are all common applications for Type V cement.

The two most common causes of failure are carbonation and chloride contamination of the concrete. Both of these lead to corrosion of the embedded steel reinforcement and as the steel corrodes it expands and exerts pressure on the concrete so that, eventually, the concrete cracks and spalls.