What do you put under a concrete base?

Gravel provides a solid foundation for your concrete as it can be compacted. It also improves drainage, preventing water from pooling beneath the concrete. While some may argue that very solid soils such as clay provide just as good a base as gravel, they still do not provide adequate drainage.

What can I use for base under concrete?

What Material is Used for a Slab Base? The base in concrete construction is usually a form of crushed stone. Most concrete contractors want a mix of coarse and fine aggregate to create a compactable base that is going to be safe for settlement and drainage.

Do you need a base under concrete?

Concrete will crack and crumble if it's not poured over a solid, stable base. Bringing in 4 to 6-in. of a good compact-able base is a good rule of thumb, but the exact amount of base a concrete driveway needs depends on the condition of the existing soil, the climate, and what you plan to park on your driveway.

What is the best sub base for concrete?

The best sub-base for a concrete slab is gravel. The soil has to be prepped first before the gravel can be laid down; pouring concrete directly onto rock is not considered a best practice. You can use different kinds of gravel for the subbase as long as it is clean and uniform in shape and size.

Should I use sand or gravel under concrete?

As a general rule, stay away from using sand as a subbase. You're better off using gravel; your concrete will last longer and have less of a chance of cracking over time.

Under-Slab Prep | Getting a PERFECTLY FLAT GRAVEL BASE for your CONCRETE SLAB FOUNDATION

Can I pour concrete directly on dirt?

Long story short, yes you can pour concrete over dirt.

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

Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.

Is gravel needed under concrete?

You do need gravel under a concrete slab, footing, or patio. Gravel provides a solid foundation for your concrete as it can be compacted. It also improves drainage, preventing water from pooling beneath the concrete.

Can you lay concrete over gravel?

Cement mix might work in some cases over an existing gravel driveway. Laying a concrete driveway over an existing gravel one is possible, but it is not generally recommended. The kind of gravel that is intended to go under cement is typically a smaller grade than what is used for gravel driveways.

How much gravel do I need under concrete?

Determine the depth of the excavation. Let's say it's d = 2 yd . Multiply the area and depth of the excavation to obtain its volume in cubic yards: 18 * 2 = 36 yd³ . The volume of gravel required is equal to the volume of excavation.

How do you prepare ground for concrete?

Can you pour concrete over rocks?

Big rocks are not a problem as long as there is uniform concrete coverage and adequate rebar for temperature fluctuations. If the big rocks protrude up above grade and if you have a few in a row, it will weaken the slab. We like things uniform, including the grade, thickness of the concrete, etc.

Do you need hardcore for concrete base?

You can't lay a concrete base directly onto soft ground, so a hardcore sub-base is essential.

How much sand and gravel do I need for a yard of concrete?

An average 1:2:3 mix contains one part cement, two parts sand and three parts gravel. To make 1 cubic yard of concrete, you'd need seven 94-pound bags of cement, about 1/2 cubic yard of sand and just over 3/4 cubic yard of gravel.

How much does it cost to pour a 24x24 slab of concrete?

A typical 24x24 garage slab costs between $3,057 and $5,944 with prices ranging from $5.31 to $8.31 per square foot for a 4” reinforced slab of concrete, and $6.83 to $10.32 per square foot for a 6” slab of reinforced concrete.

How thick should the base be for a concrete driveway?

Most residential concrete driveways are 4” thick and placed on a compacted 4” to 8” thick base of gravel or crushed stone. Adding rebar can double or almost triple the strength of a standard 3,000 PSI concrete driveway. Increasing to 5” will increase the strength by about 50%, and even more with rebar.

How thick should a concrete base be?

In general, 6 inch (150mm) slab thickness is considered for residential and commercial buildings with reinforcement details as per design.

Is 3 inches of concrete enough?

A concrete patio slab should be at least 4 inches thick and have a compressive strength of 3,000 PSI. You're free to make it thicker or stronger, but unless specifically required for your patio build, it's likely overkill to surpass 4 inches in thickness.

Can you pour concrete over grass?

Cheap and versatile and easy to pour, concrete will last you years down the road. You can pour it just about everywhere—including on the grass. Although it takes a little work, pour concrete over grass to create that walkway you always wanted or that mowing preventative you could previously only dream about.

Do you need a rebar for a 4 inch slab?

For 4” concrete slabs used for driveways and patios, #3 rebar is common. Driveways that will support daily traffic by heavy trucks frequently use 1/2″ or #4 steel bar.

Do I need to compact soil before pouring concrete?

The soil you build your concrete pad on needs to be compact and well-drained to ensure the best concrete slab results. Concrete is a porous material so drainage can't be an issue. Otherwise, water under the concrete pad will result in stress cracks in the cement as the ground flexes.

Should I water ground before pouring concrete?

It will expand when wet and shrink when dry and your concrete slab will be a disaster. Best to get as much clay removed as possible, compact the sub-grade evenly, and make sure to water the ground before placing the concrete.

What kind of plastic goes under concrete?

The most commonly used vapor barrier under concrete slabs is polyethylene (poly) plastic sheeting with a thickness of 10 mil or 15 mil.