A slab is only as good as what sits under it
A slab looks like the simplest thing we pour. Flat, gray, no pattern. That is exactly why people get them wrong. A shed slab poured right on topsoil, a hot tub pad with no steel, or a garage floor over two inches of sand fill on clay will all look fine for about a year. Then one corner drops, a crack runs straight across, and the shed door stops closing.
In Aurora, the usual culprit is clay. It swells when wet and shrinks when dry, and a slab sitting on it moves unless the base is built to handle that. We dig out soft soil, compact road base, and pour a 4 inch slab of 4,000 PSI air-entrained concrete with rebar or fiber. Joints are planned, not guessed.
Typical pricing runs $7 to $11 per sq ft. A 12x12 shed slab (144 sq ft) usually lands between $1,000 to $1,600. Garage floors are priced separately and covered below. This page sits under our residential concrete services.
What kind of slab problem do you have?
New slab or failing one, this is how we sort it out.
Call soon if you see
- A garage floor that has dropped, heaved, or cracked so water runs the wrong way
- A slab that has pulled away from the foundation or the shed wall
- Cracks wide enough to catch a shoe, or one side noticeably higher than the other
- A hot tub or AC unit sitting on a pad that tilts
- Standing water on a slab that used to drain
Usually safe to watch
- Hairline cracks that have not changed in a year
- Light surface dusting or small spots from oil
- A crack along a saw-cut joint, which is what the joint is for
- Surface stains that do not affect the slab
What we pour slabs for
Sheds and outbuildings
A shed needs a flat, solid pad that stays flat. We size it a few inches bigger than the shed footprint and slope it slightly so water drains away from the door. A concrete slab keeps the floor dry and lasts longer than a gravel pad.
Hot tubs
A filled hot tub weighs several thousand pounds. We thicken the slab, add rebar, and keep it dead level so the cabinet does not rack. Check your manufacturer's specs for the pad.
AC pads and equipment
An air conditioner needs a level pad so the compressor does not vibrate and the condensate drains properly. A small slab fixes a tilted unit.
Basketball courts and open pads
A court is a big slab that gets pounded. We space joints carefully, reinforce it, and finish it with a light broom texture. For a driveway-style pad, see concrete driveways. For vehicles, see RV and parking pads.
Slabs next to the house
A patio-style slab next to the house is a different job with its own slope and drainage. See concrete patios.
Garage floor replacement
A garage floor is a slab that works hard. Cars, jacks, tool chests, snowmelt dripping off the bumper, and a floor that is often the lowest point of the house. When it fails, it fails in obvious ways. A crack runs from the door to the back wall. One side sinks an inch. The corner by the door heaves. Water that used to run out now puddles.
Garage floor replacement runs $9 to $14 per sq ft. A 2-car garage floor (about 440 sq ft) typically lands between $3,950 to $6,150. It covers breakout, a rebuilt base, a vapor barrier, a 4 inch 4,000 PSI slab, and saw-cut joints.
Why they crack, sink, and heave
Many garage slabs were poured on loose fill or thin sand over clay. When the clay swells, the slab lifts. When it dries, the slab sinks. Cracks form because there was no plan for where the slab could move. Water that gets under the slab keeps feeding the problem.
What a proper replacement includes
We break out the old slab and haul it away. We dig out soft soil and compact road base. A vapor barrier goes over the base so ground moisture does not wick up through the floor. Then we pour a 4 inch slab and cut control joints with a saw soon after finishing, so the slab cracks along the lines we picked. We also cut an isolation joint at the foundation wall, so the floor and the house can move on their own without cracking each other.
Lifting instead of replacing
If the slab is mostly sound and only one area sank, lifting can be cheaper. See concrete leveling and mudjacking. If the floor is cracked in many places and has moved more than once, replacing it is the better buy.
Concrete, not coatings
We do concrete work. We do not apply epoxy coatings. Once the new floor is cured, you can have a coating installed by someone who does that work, or leave it as a sealed broom finish.
How we pour a concrete slab
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Plan the size, slope, and joints
We measure, mark the layout, and plan the drainage and joint spacing.
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Excavate and compact
We remove topsoil and soft fill, then lay and compact road base. Clay sites get extra depth.
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Forms and reinforcement
Forms set the edges and thickness. Rebar goes in on chairs, or fiber is mixed in, depending on the slab.
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Pour and finish
We place 4,000 PSI air-entrained concrete about 4 inches thick, then screed, float, and broom it. Control joints go in every 8 to 10 feet.
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Cure and use
Walk on it the next day. Cars after about 7 days, heavy loads closer to 28 days. Seal after about 30 days.
What affects the price of a concrete slab
Slabs run $7 to $11 per sq ft, and garage floors run $9 to $14 per sq ft. These are the things that move the number.
- Size and thickness
Bigger slabs cost less per square foot. Hot tubs and heavy loads need thicker concrete and more steel.
- Site prep
Slopes, clay, and soft fill add excavation and base material.
- Removing old concrete
Tear-out and haul-off run about $3 to $7 per sq ft. That is part of any garage floor replacement.
- Finish type
Broom finish is standard. A smoother trowel finish suits a garage. Color adds cost.
- Access
A shed in a backyard behind a narrow gate means wheelbarrowing, which adds labor.
- Reinforcement and vapor barrier
Rebar and a vapor barrier add material and labor, and they are worth it.
Pouring slabs through the Aurora seasons
Winter
A frozen subgrade cannot be compacted, and fresh concrete cannot freeze for its first days. Most slab jobs go better in spring.
Spring
Spring is busy. Wet clay can delay the dig after a storm.
Summer
Heat and wind dry slabs too fast. We pour early and cure right away.
Fall
Fall is a good time. Seal before the first snow, and keep deicers off the first winter.
Aurora soil, salt, HOAs, and permits
Expansive clay soil
Clay moves, so we rebuild the base and plan joints. Keep downspouts and sprinklers away from slab edges.
Deicing salt
Garage floors take salt from every car that comes home in winter. Air-entrained mix and a penetrating sealer help. See concrete sealing.
HOA approval
Many HOAs have rules about sheds, hot tubs, and outbuildings, including location and size. Get approval before you pour.
City of Aurora permits
Permit needs vary by structure, and hot tub electrical is its own question. We confirm with the City of Aurora Building Division for your address.
Concrete Slabs and Garage Floors FAQs
How much does a concrete slab cost in Aurora?
Typical pricing is $7 to $11 per sq ft. A 12x12 shed slab (144 sq ft) usually runs $1,000 to $1,600.
How much does garage floor replacement cost?
Garage floor replacement runs $9 to $14 per sq ft. A 2-car garage floor (about 440 sq ft) typically costs $3,950 to $6,150.
How thick should a shed slab be?
Four inches works for most sheds. Heavier loads like a hot tub or equipment need more thickness and steel.
Why is my garage floor cracked and sinking?
Usually the base. Garage slabs poured on thin fill over clay move when the clay does. Water under the slab makes it worse.
Do you do epoxy garage floors?
No. We pour and repair concrete. A new floor can be coated afterward by a coating contractor, once it has cured.
How long before I can park on a new slab?
Cars after about 7 days. Heavy trucks wait closer to 28 days.