Question: Can I Pour Concrete Over Dirt?

What type of gravel goes under concrete?

Backfill beneath concrete flat-work along foundation walls should be accomplished with a granular material that is uniform in size.

Some fill materials, such as round stones like pea gravel, tend to be self compacting.

“I recommend open-graded granular material be used,” says Tull..

Do you need a vapor barrier on concrete?

You’ll typically need a vapor barrier if you’re installing flooring over concrete. Therefore, in high-humidity areas, moisture will move to a relatively low-humidity area, even through concrete. … This way you can stop the vapor drive of water upward to your floors, protecting them from any damage (source).

How do I keep my concrete floor from sweating?

How to stop concrete sweatingDry out the room by air movement: a high volume low speed fan works well.Turn down the air conditioning/turn up the heat to keep the concrete floor temperature and the air temperature at similiar levels.Use a dehumidifier to remove moisture from the air and reduce the condensation.More items…•Feb 20, 2014

What time of year is best to pour concrete?

springLate spring and early fall are typically the best times to pour cement, as the weather generally is mild. You also might be able to do a concrete project during the summer, as the temperature doesn’t often pass 90 degrees Fahrenheit.

When can you not pour concrete?

Experts agree that the best temperature to pour concrete is between 50-60 °F. The necessary chemical reactions that set and strengthen concrete slow significantly below 50 °F and are almost non-existent below 40 °F.

Can I use pea gravel under concrete?

If you use pea gravel beneath a patio, take a few simple steps to ensure the stability of the base before setting your surface stones, pavers or bricks. Click to see full answer. … It should be ok to pour concrete over your gravel walk although you might want to give the concrete a little more depth along the sides.

What is the lowest temperature you can pour concrete?

Experts agree—the best temperature to pour concrete is between 40° – 60°F. When temperatures dip below 40°F, the chemical reactions that strengthen concrete slow down and can lead to weaker concrete.

Do you need gravel under concrete?

Whether you pour concrete for a walkway or patio, a strong gravel base is required to prevent the concrete from cracking and shifting. Gravel is especially important in clay soil because it doesn’t drain well, which results in water pooling under the concrete slab and slowly eroding the soil as it finally drains.

Should you put plastic under concrete?

Recently, though, research has shown that the old traditional layer of 6-mil Visqueen (polyethylene plastic) under the slab is seldom effective for two main reasons: Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through.

How deep should I dig for a concrete slab?

Excavate the slab area to a depth of about 7 inches, allowing 3 inches for a gravel base and 4 inches for concrete.

Can I pour concrete in a hole full of water?

Concrete will set just fine under water. The best way to do it is to use a sleeve to place the concrete in the bottom of the hole first, then displace the water, rather than simply pouring it in, although that will work too. “rather than simply pouring it in, although that will work too” your words.

What if it rains after pouring concrete?

Heavy rain can cause problems to freshly poured concrete as it can wash out some of the cement from the mix. This can weaken the surface of the concrete, making it a softer consistency and decreasing the strength of the concrete.

Can you pour concrete on muddy ground?

Damp ground will not be a problem unless is can not support the weight of the concrete. Cement/concrete does not “dry” , it cures , a chemical reaction. It absorbs water to cure, as noted , some concrete applications are sprayed with water to aid the cure.

Is sand a good base for concrete?

Pour concrete over a solid, well-drained base of sand or gravel over clay and other poorly draining soils to provide even support.

How long does it take for 4 inches of concrete to cure?

When waiting for concrete to dry, keep these timeframes in mind: 24 to 48 hours – after inital set, forms can be removed and people can walk on the surface. 7 days – after partial curing, traffic from vehicles and equipment is okay. 28 days – at this point, the concrete should be fully cured.

Will concrete dry if too wet?

When a concrete mixture is too wet, it causes a greater amount of shrinkage during the drying process than is needed. As a result, the concrete has a great likelihood of cracking and for those cracks are likely to be a fairly good size. … A watery mix actively reduces the compressive strength of the dried concrete.

Why do you 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.

Do you need rebar for 4 inch slab?

No, you do not need rebar for a 4-inch slab of concrete on grade. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Rebar is recommended on concrete measuring 5 – 6 inches thick.