Can You Pour Concrete Over Gravel?

Concrete is known as a primary building material, used more commonly than any other material worldwide. In case you’re thinking of putting concrete over gravel, reading this post first might be wise. We’ve done some research to put your mind at ease in knowing how to best use concrete over gravel.   

Concrete can be combined with various substances in different building tasks. As individual materials, placing concrete over gravel is acceptable, especially for those slabs laid atop clay soils that are prone to too much moisture.

However, laying concrete over gravel still depends on the following factors: 

  • Purpose and function 
  • Size and texture of gravel   
  • Different types of gravel you can use

Let us now walk you through the details as you consider pouring concrete over gravel while thinking of other related matters that come to mind. Kindly read on for a better understanding.     

A foundation of a road before pouring concrete, Can You Pour Concrete Over Gravel?

Gravel is Useful Under Concrete Slabs

  1. With enormous spaces in between, gravel can block water from going up the concrete slab doing away with wet surface marks. 
  2. Flattening the ground is easier, making it even simpler to measure the amount of concrete required since gravel has the flexibility to be compressed. 
  3. Dense gravel can serve as an effective water drainage system for concrete slabs preventing soil erosion and eventual cracking.    

Right Size and Texture of Gravel to Use Under Concrete  

Regarding gravel stones' sizes, ¾ inch to 1 inch would be ideal enough, even though there may be instances that this size range would still be inappropriate when roughness is factored in. Furthermore, dimensions beyond 1 inch will be excessively leaky, making it difficult to determine the desired quantity of concrete.      

In terms of gravel texture, you have a choice between rough and fine, with the latter normally measuring not more than 9.5mm and the former going between 9.5mm to 38mm. It is also advisable to go for gravel that is more than 20mm thick as this may be your best size option in combination with concrete.       

Types of Gravel to Choose From 

There are wide gravel varieties available on the market, but here’s a list of the four most common types that you can pour your concrete onto, together with their descriptions, applications, and advantages: 

Pea Gravel

Pea gravel stones

The screened type is on top of the list of the most sought-after gravel categories and pea gravel fits that bill. These are round pebbles the size of a pea, as its name implies. Easy to maintain and an alternative weed controller, these stones work best for gardens and other landscaping developments as they are kept in check two inches below the ground.      

Washed Clean Stones 

Basically, pea gravel also falls under this distinction. Washed gravel is washed clean stones whose luster makes it a standard choice for ornamental purposes. Polished to perfect cleanliness, this type is the favorite gravel among builders and consumers effectively addressing concerns on drainage, weeds, maintenance, and affordability.

White Marble Chips 

White marble chips

Mostly prominent in pathways and driveways, you can distinguish these stones from other gravel types with their unique color (having lines of gray on top of being off-white or brilliant white) and a wide array of names (white marble stone pebbles, white limestone, white ¾-inch stone, etc.).

Whether living in hilly terrain or sprucing up your lawn, these rocks will come in handy as they prevent soil erosion and weeds before they even become problems. 

Crushed Stone 

Crushed stone for road building material gravel

Used for general construction purposes, this must be the most suitable gravel material that can be put under concrete as these angular rocks are particularly used in roadwork, which includes railroad assembly and tarmac maintenance. Crushed stones can be utilized in the forms of trap rock, granite, dolomite, and limestone.             

How do you stabilize gravel? 

To stabilize gravel would necessitate using gravel stabilizing grids to better hold gravel particles into place within its structure, providing a solid footing. This makes for a steady finish in some driveways, walkways, or parking lots.

How thick should a concrete base be? 

Concrete base in an excavation for a house

You can settle for the basic 4-6 inch concrete base or go up to as wide as 20 inches. Your chief consideration would be about the budget. The purpose of the structure whether it will be designed as a residential or business property is also an issue.

Moreover, it is imperative for you to study the concrete slab’s thickness according to local building codes. Understandably, authorities are expected to abide by regulations as regards the geographical conditions of the site wherein you intend to have the base constructed.    

What is the thinnest concrete that can be poured?

A strong groundwork is a must-have for any structure to stand the test of time. For the most part, you can go anywhere from four inches to six inches for your concrete base. Avoid making it thinner than four inches especially if you want to have the peace of mind of being assured that you are standing on steady ground. 

Can gravel be used for a foundation? 


When it comes to the layering requirement, it is good to have more gravel under concrete, as much as possible, because it makes the foundation firmer. In this way, you can target a gravel thickness of four to six inches. Otherwise, you can stick with the normal concrete slab of four inches over a gravel base of three inches.        

A gravel foundation serves as drainage through which water can pass while absorbing it to protect your most prized structure from outpours and splashes at the sides. When flooring or patios are concerned, compressed gravel underneath is ideal as it can reinforce the concrete base making it steadier while avoiding cracks and shifts. 

Final Thoughts

Pouring concrete over gravel is a rock-solid way to make any of your foundations as tough as they can be. Just stay in line with these guidelines and your construction plan will never go wrong.      

Do you have other questions about pouring concrete? Check out our informative posts on this subject:

Can You Cement Or Pour Concrete Over Brick?

How Thick Should Concrete Be For A Patio?



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