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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.
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.
Can you pour concrete directly on dirt?
Long story short, yes you can pour concrete over dirt.
How many inches of gravel do you need 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 you pour concrete without a gravel base?
4 Answers. Is gravel absolutely required NO but it is a good idea. Most the time i see slabs poured directly on earth the owners are doing it themselves and the base is not level or has holes. If a slab is not a uniform thickness this can cause cracks even with reinforcement of fiberglass, mesh or rebar.
Should you put plastic under concrete?
A concrete vapor barrier is any material that prevents moisture from entering a concrete slab. Vapor barriers are used because while fresh concrete is poured wet, it’s not supposed to stay that way. It needs to dry and then stay dry to avoid flooring problems. This is why a vapor barrier under concrete is essential.
What kind of gravel goes under concrete?
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. Crusher run (a mix of crushed stone and stone dust) is one of the best base materials for concrete flatwork.
Can I use pea gravel under concrete?
If the soil is disturbed and packed or unstable such as some clays, a base will provide a solid underpinning for the slab. If you use crushed rock and dust, it will need to be packed. It will pack substantially. Pea gravel, on the other hand won’t pack.
Is sand a good base for concrete?
Answered by LCD: Sand is a proper levelling course for use under pavers and ungrouted brick patios and such. It is definitely NOT a proper base for a driveway – it is too mobile, has low bearing capacity, moves about under load especially if very dry or very wet, and will cause structural cracking of your driveway.
How do you prepare the ground for a concrete garage floor?
Good ground preparation starts with removing the topsoil. Then, if the soil has not previously been “disturbed” (i.e., dug up), a four-inch layer (minimum) of gravel or stone should be added. (Soil that has been dug up before should be compacted.) The gravel or stone also needs to be compacted.
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. All Americover Vapor Barriers are composed of virgin polyolefin resins and offered in 10 mil, 15 mil, and 20 mil.
Can moisture come up through concrete?
Concrete’s porous nature means that water from under your home can seep up through your concrete floor, making it damp. Basements and garages – the typical rooms with concrete floors – also suffer from poor air circulation, giving the moisture nowhere to go once it seeps through the floor.
What do you put under cabinets on concrete?
You should install an insulating underlayment product that is the same height as the finished flooring. If you install wood product directly on concrete, the moisture in the concrete will wick up into the cabinets and ruin the parts in contact with the concrete.
Is crushed concrete better than gravel?
Crushed Concrete driveways are a much more cost-effective driveway solution compared to gravel driveways, regular concrete driveways, or asphalt driveways. With benefits like the price, sustainability, and the fact that it can never crack and require a repair, crushed concrete is a great driveway option.
What should I put under pea gravel?
Start with a heavy tamper to compress any soil underneath, add a sturdy base layer of either crushed rock or sand, layer on about 3 inches of pea gravel, and then tamp down again to make sure everything is compact. A sturdy base is especially important for gravel driveways.
Can you sprinkle concrete on gravel?
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.
Is it cheaper to pour your own concrete?
One of the least expensive ways to get concrete is to mix your own. You can buy bags of the mix from a home improvement store. Typically, you only have to add water for it to be ready to pour. Otherwise, you risk getting a weaker concrete once it cures, which could lead to cracks or crumbles within a couple of years.
Does 4 inch concrete need rebar?
Rebar is not necessary for every concrete project. The general rule of thumb is that if you are pouring concrete that is more than 5 inches in depth, you are probably going to want to add in some rebar to help reinforce the entire structure.
Should I use cement or concrete?
Concrete works well in larger projects, while cement is more often used in smaller jobs. One of the strongest and longest-lasting materials known to man, concrete is used to build schools, bridges, sidewalks, and countless other structures. But you don’t need a hard hat to have success with concrete.
How do you keep moisture out of concrete slab?
Methods Used to Stop Moisture in Concrete Floors Low-permeance Vapor Barrier or Retarder. Allow Natural Drying of Concrete Slab. Keep Excavation Free of Water. Apply Damping Agent for Existing Concrete Floor.
How do I know if my concrete floor has moisture?
By comparing the weight of the calcium chloride before and after the test time (60 to 72 hours), it indicates not just whether moisture is present, but the quantity and rate of moisture vapor travelling upwards through the slab. Kits typically measure the moisture in the top ½ inch or ¾ inch of the concrete slab.
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).
Is crushed concrete safe?
Crushed concrete is not listed as a carcinogen by the National Toxicology Program (NTP), OSHA or the International Agency for Research on Cancer (IARC). However, crystalline silica is now classified by IARC as a known human carcinogen (Group 1). Prolonged and repeated breathing of silica may cause lung cancer.
Is crushed asphalt cheaper than gravel?
Asphalt driveways typically cost $2 – $5 per sq foot to install – more than gravel, but much less than many other options. Long lifespan. With proper maintenance, an asphalt driveway will last anywhere from 12 – 35 years depending on installation, climate, usage and other factors.
Is crushed concrete Dusty?
Crushed concrete is very dusty. If you have no intention of pouring concrete ever, go with regrind asphalt. Beware when it packs you won’t be able to shave off an inch here or there. It’ll just come out in chunks however thick it was put down.
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.
Can you pour concrete directly on dirt?
Long story short, yes you can pour concrete over dirt.
How many inches of gravel do you need 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 you pour concrete without a gravel base?
4 Answers. Is gravel absolutely required NO but it is a good idea. Most the time i see slabs poured directly on earth the owners are doing it themselves and the base is not level or has holes. If a slab is not a uniform thickness this can cause cracks even with reinforcement of fiberglass, mesh or rebar.
Should you put plastic under concrete?
A concrete vapor barrier is any material that prevents moisture from entering a concrete slab. Vapor barriers are used because while fresh concrete is poured wet, it’s not supposed to stay that way. It needs to dry and then stay dry to avoid flooring problems. This is why a vapor barrier under concrete is essential.
What kind of gravel goes under concrete?
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. Crusher run (a mix of crushed stone and stone dust) is one of the best base materials for concrete flatwork.
Can I use pea gravel under concrete?
If the soil is disturbed and packed or unstable such as some clays, a base will provide a solid underpinning for the slab. If you use crushed rock and dust, it will need to be packed. It will pack substantially. Pea gravel, on the other hand won’t pack.
Is sand a good base for concrete?
Answered by LCD: Sand is a proper levelling course for use under pavers and ungrouted brick patios and such. It is definitely NOT a proper base for a driveway – it is too mobile, has low bearing capacity, moves about under load especially if very dry or very wet, and will cause structural cracking of your driveway.
Do you need gravel under concrete fence post?
Concrete is the most secure material for setting fence posts, especially if you have sandy soil. Gravel may be okay with dense, clay-heavy soil, but in looser soil, concrete is the only thing that will truly keep your fence posts stuck in place.
How do you prepare the ground for a concrete garage floor?
Good ground preparation starts with removing the topsoil. Then, if the soil has not previously been “disturbed” (i.e., dug up), a four-inch layer (minimum) of gravel or stone should be added. (Soil that has been dug up before should be compacted.) The gravel or stone also needs to be compacted.
Can you sprinkle concrete on gravel?
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 do you prepare the ground for a concrete slab?
Preparation is the most important aspect of pouring a concrete slab. Dig the ground down to the proper depth. Smooth out the ground with the flat side of a rake so that you have a level surface. Tamp the ground with a hand tamper or mechanical tamper. Pour 2 inches of small, rounded gravel for additional drainage needs.
Is it cheaper to pour your own concrete?
One of the least expensive ways to get concrete is to mix your own. You can buy bags of the mix from a home improvement store. Typically, you only have to add water for it to be ready to pour. Otherwise, you risk getting a weaker concrete once it cures, which could lead to cracks or crumbles within a couple of years.
Should I wet gravel before compacting?
Try and wait for the ground to dry if it is a little wet before compacting, but if its unavoidable, add a small amount of large gravel to help bind the wet surface and continue compacting.
Can you pour concrete on clay?
The clay can compress under the weight of the concrete, causing the slab to shift or sink over time. It also can leach moisture from the concrete itself, resulting in uneven curing and a brittle base. With proper preparation, however, it’s possible to pour a slab on clay soil without encountering these problems.
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. All Americover Vapor Barriers are composed of virgin polyolefin resins and offered in 10 mil, 15 mil, and 20 mil.
Can moisture come up through concrete?
Concrete’s porous nature means that water from under your home can seep up through your concrete floor, making it damp. Basements and garages – the typical rooms with concrete floors – also suffer from poor air circulation, giving the moisture nowhere to go once it seeps through the floor.
What do you put under cabinets on concrete?
You should install an insulating underlayment product that is the same height as the finished flooring. If you install wood product directly on concrete, the moisture in the concrete will wick up into the cabinets and ruin the parts in contact with the concrete.
Is rebar needed in concrete driveway?
The presence of rebar in a concrete project gives the final project considerably more strength than concrete alone. This strength is crucial for things like buildings, roads and driveways. Rebar is not necessary for every concrete project. Wire mesh use is becoming much more common for projects like a home driveway.
