How Thick Should A Concrete Slab Be For A Garage? (Answered & Much More) 

Last Updated on September 28, 2022 by

A garage concrete slab should be at least four inches thick. If heavier machinery is placed on it, the thickness of the concrete slab can go up to 12 inches. However, every country has building codes that help direct the right concrete mixture based on slab thickness. 

Building codes have set up different rules and regulations to ensure that a certain level of quality is maintained. Before you rebuild or build your garage, you should be conversant with those rules. They might change depending on the state you live in, but they all ensure all buildings are structurally strong. 

A garage floor can get damaged more often than other parts of your house. Cars and heavy equipment placed in the garage contribute to the destruction of the concrete slab. With the garage being the center point for most activities that can damage your floor, it is essential to ensure that you take care of it. 

Here we explain the ideal thickness of a concrete slab for a garage to help you during construction. 

Keep reading!

What Determines The Thickness Of A Garage Slab?

The thickness of the concrete slab is not always uniform in all garages. Various factors influence the decision on its thickness.

Some of this includes:

1.Type Of Load To Be Placed On The Slab

A thicker concrete floor will hold heavier loads and vice versa. The standard thickness of a garage slab can range from 4 to 6 inches, but for a home garage for personal cars, you might not necessarily need does not need a 6 or 8 inches slab. 

However, you can determine the thickness of the slab based on the type of load as follows:

Light Loads; this can be two cars and a truck. The thickness of this slab can be at least four inches thick.

Medium Loads; such a load can be equal to an average-sized vehicle or medium to heavy trucks. This concrete slab should be six inches thick.

Heavy Loads, if your garage is going to house heavy cars constantly, the thickness of your concrete floor can be from 6 to 8 inches. The concrete slab also requires sealing to ensure that the load does not crack the slab.

2. The Span Of The Concrete

For a small portion of the garage, the thickness can be 4 inches and withstand huge amounts of pressure. When the span of the floor increases, the thickness should increase.

3. Design Mix Of The Concrete

Concrete comes in different types. The type you choose for your garage should be compatible with the thickness you want your garage slab to have.

Here is the table to guide you when deciding on how thick your concrete slab based on load

Garage forSlab thickness
Light load Minimum thickness of 4 inches
Medium load Minimum thickness of 6 inches
Heavy load The thickness of 6-8 inches
Parking 4-12 thick based on expected load 
Determines The Thickness Of A Garage Slab

How Thick Should A Residential Garage Floor Be?

For a residential house, your concrete slab should be 6 inches thick. A 6-inch concrete slab can withstand most of the tasks in a garage.

The 6-inch thickness also applies to commercial or public garages as it is adequate to hold any size car. Companies with heavy cars, like tractors and excavators, need a thicker concrete floor. They can have up to 8 inches thick slabs to accommodate the heavy machines.

Do I Need To Reinforce My Concrete Garage Slab?

Typically not all concrete slabs require reinforcement with rebar and wire meshes. Some can be made of concrete alone and comfortably hold the weight placed on them. For your home garage, there is no need to add reinforcements.

Rebar and wire mesh are added to the concrete when pouring to increase its strength and resist cracking. Reinforcement is done on the floors that will have constant pressure on them, like companies dealing with huge trucks. 

If you opt to reinforce your concrete with a rebar or mesh wire, you need to get a permit from the government department in charge of construction.

What Type Of Concrete Is Best For Your Garage Floor?

Floor concrete comes in various types, and you should know which will best suit your needs. The ones suitable for garages include: 


ST3 is a common type of concrete used in unreinforced floors like a home garage or house floor. It is the best choice for all light-duty floors. 


The ST4 concrete is a strong and more durable unreinforced concrete. It offers more strength and durability than the ST3.


This concrete is also used for domestic use and is the strongest ST concrete option, thus, the most suitable for a garage floor. ST5 can also be used on floors that need reinforcements.


Among the types of concrete that do not require reinforcements, this is the strongest of them all. It is used for domestic applications and can be covered with a permanent flooring finish.

Reinforced concrete

The best types of reinforced concrete are RC20/25 and RC28/35. They are made to withstand harsh weather and wear from the human tread. This is the best choice for heavy-duty garages. 

Reinforce  Concrete Garage Slab

How Much Does It Cost To Pour Concrete On A Garage Floor?

The overall cost of pouring the concrete in a garage floor installation depends on the following factors:

1. Slab thickness

2. Garage size

3. Extra dirt work

4. Material cost

5. Reinforcement material cost if there is any needed

6. Grading of the sub-base

7. Permits and inspections

However, on average, pouring a concrete floor cost about 4 dollars to 6 dollars per square foot, including the labor. This adds up to 3,600 dollars or 7,200 dollars for a 30feet by 30feet, 6 inches thick slab. You can use the average per square foot to estimate the garage slab cost. 

N /B: Different states have different rates for pouring concrete floors. If you want the actual figure, pay a visit to your local contractors for their prevailing rates.

Tips For A Better Garage Floor Slab

1. Preparation Of A Base

A solid and level base for your garage floor is important. When it is uneven, it predisposes the garage floor to crack. When you fill the base with soil, it has to be compacted well to ensure no settlement after the floor has been built. 

The type of cars to pack in your garage determines how thick the concrete will be. A 40mm aggregate concrete base on the soil on which the garage will be built can be helpful to build a strong base.

2. Erecting A Formwork 

A formwork is built to withstand construction load, the pressure of fresh concrete, and the weight of the contractors working on your garage.

3. The Right Concrete Mixture

Concrete is a combination of water, cement, ballast, and sand. These ingredients determine the strength of your concrete floor. 

If you put a lot of water into the concrete mixture, it makes it easier to pour but ends up making your slab weak. However, you can add plasticizers into the mixture and make it easier to pour without losing the quality of the end product. Contractors know about this, and they mostly incorporate it when making concrete slabs.

The concrete mix should have air entertaining agents if you live in cold areas. The agents limit damage to the slab in the cold season. You can also incorporate fiber reinforcements to help increase the concrete slab’s strength during the cold season.

3. Placement Of Reinforcement

If you intend to park heavy vehicles in your garage, you should lay steel bars before the concrete for reinforcement. The steel holds the floor slab together and in place to avoid breakage and cracking. Besides, reinforcing all garages is the best option if you are not on a limited budget. 

4. Concrete Placement

Always mix the concrete to the right ratio, keeping in mind the climatic condition. Leave the mixture for about 90 minutes, and then pour it in. Use the hand vibrators to ensure that the concrete compacts properly.

5. Garage Floor Finishing

Use a good finish for your garage to leave it looking nice and protect against water damage. The floor finishes you can use on the garage are polished concrete flooring, garage floor tiles, garage floor mats, garage floor paint, and garage floor epoxy. 

6. Slab Curing 

Take enough time to cure your garage slab to make it stronger for years to come. The easiest and most effective way is the water cure. Use a mist or ponded sprayer to pour water on the slab at least 5-10 times a day or simply ensure the slab is flooded throughout the day. Do this for a minimum of 7 days and a maximum of 28 days after installation.   

Final Thought

A garage concrete slab should be thick enough to support the load placed on it without cracking. The thickness of the garage slab can start from 4 inches to 8 inches. You can reinforce the slab to make it stronger, especially for commercial garages. For a residential garage, you can use unreinforced concrete, and the slab will hold the weight of up to three personal cars. 


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