Concrete Slab: How To Build One

The concrete is set directly on the ground. It doesn\’t have a base or concrete walls beneath it or surrounding it. In Maine we have a large amount of slabs-on-grade to build houses and garages.

A slab foundation will typically be more affordable to construct than a concrete wall foundation, which includes concrete floors.


The most crucial element of making an slab is the preparation of the sub-grade. If you don\’t have an adequate foundation, the concrete is likely to be prone to crack and settle.

There\’s a lot frost in the soil in the area I reside. It\’s not unusual for ground to get frozen to as much into the ground as far as 4 feet. If someone asks me how best to make the base of gravel of their slab, I suggest:

1. If you don\’t already have a quality base for your gravel, remove the \”bad\” dirt and replace it with a high-quality crushed gravel.

I would recommend going at least as far as you can go that is in the area you live in. If you don\’t have freeze-thaw cycles, the 12\” up to 24\” base will be adequate.

2. Compact or roll the gravel into twelve\” lifts to keep the slab from sinking.

3. Use a laser level to make the final dirt level. This ensures a consistent slab layout and setting your forms much more straightforward.

The majority of the Concrete slabs we mix are about 6\” thick. If you are building a home or commercial garage, we can increase the thickness until 12\”.

The process of shaping the edges of slabs is crucial. We prefer 2×6\’s in most residential uses. We make use of 2×12\’s to create the edges when they are more thick.


1. Lay all the boards along the perimeter as straight as you can.

2. Use nailing boards that are approximately 3 feet long. Make sure they\’re at minimum 1 1/2\” larger than the slab\’s dimensions, so that you can join them.

3. Set the boards on an edge and measure the lengths and mark the slab\’s dimensions for each one. Then nail the boards together.

4. Once you have your box put together and placed, take a measurement diagonally from corner-to-corner in order to make the slab square. You must have the same measurements in all directions to ensure that the slab is square.

5. The next step is to secure the corners with either metal or wooden stakes to ensure the boards won\’t be off the square.

6. Install a nail at every corner, and then use a string to go through the outside edge of the boards in order to straighten the boards.

7. Completely staking the boards, with the help of the string reference. I prefer a straight edge. Builders tend too.

8. Utilize a laser level to set the boards at the proper level. It is possible to raise them up a bit or go beneath them to reach the right height. Attach the boards to stakes once they are in good shape.

9. Backfill the boards with gravel to make sure they don\’t move after the concrete has been put in.

10. This is it! The forming has been completed.

What kind of reinforcement is the most effective?

I\’ve had lots of success using a mixture of wiremesh, rebar, and fibermesh. Click on each one if don\’t know about the other.

When I put in reinforcement, I always set an extra row of rebar on the edges. In the case that the sides are more than 12\” thick, I would put two rows near the top, and a second row down the middle and set the bricks on top.

If it\’s commercial concrete, I will attach an rebar mat 12-16 inches on the center of the floor and use bricks or chairs to hold it within the concrete.

I incorporate fibermesh into every thing we put in. Wire mesh is great when you lift it above the ground with bricks or chairs. Sometimes I\’ll mix both of them if cost isn\’t a problem.

There\’s only one chance to get it correctly, so a bit of excessive is fine according to me.


In Maine I am required to pour concrete in cold temperatures for four months of the year. I mix a special design that helps my concrete to set up quicker.

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