Home / Home Improvement / How to Produce Crack-Free Concrete Slabs?


Concrete is an excellent construction material that’s used in everything from simple patios to the tallest skyscrapers. It’s extremely strong with high tensile and compressive stress, durable against weather and fire, and quite cheap and accessible.

The one drawback with concrete is that they need to be poured and cured properly in order to prevent cracking while it sets. In this article, we’re going to give you some preparatory tips that’ll help ensure that your concrete slab is crack-free.

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Construct A Stable Base

Concrete will need a stable base if it is to set properly, without any cracking or crumbling. Typically, the base will be about 4 to 6 inches high but the exact quantity depends on factors like the state of the soil underneath, the climate of the area you live in and what kind of load the slab will have to endure on a daily basis.

For instance, if you live in a colder climate and expect the slab to endure heavy traffic, then you should ideally have a base layer that’s around 12 inches tall. The same applies if you’re planning to pour the concrete over clay or organic soil.

Compact Your Base Well

When you’re compacting base, it’s best to use a vibrating plate compactor instead of the kind that’s known as ‘jumping jack’. Ideally, you should compact the base every time you add a layer of two inches.

Add A Little Moisture

If you’re base is really dry, then it won’t compact well. Hence, you should spray it gently with water with every two-inch layer. Here’s a simple test to ensure that the base is moist enough: take a handful and try to mould it into a ball. If the shape is retained, then you’re okay to proceed. If it keeps crumbling, then more water is required. However, make sure you don’t spray so much water that it starts to create puddles.

Make Sure the Forms Are Straight

If you don’t want your slab looking uneven, then you must ensure that forms are setup straight. The best way to do is install two screws at both ends of each form board and then stretch a string between the two. This string will be your guide as to how you should position the boards.

Working with Rebar

Rebar is used to reinforce concrete, most often by constructing a support grid. Typically, the grid consists of 2-foot squares comprised of rebar that a half an inch thick. The rebar is commonly tied together with tie-wire twister and you should make sure that they are enough ties to ensure that the grid always stays intact.

You’ll have to cut the rebar into length to make the 2-foot grid pattern. This is often done using a diamond masonry blade that you can get in your local stores. If you need to bend rebar, you can use a simple rebar bender.

If you follow the above preparatory tips, you should be able to produce concrete slabs that are completely crack-free.

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