Concrete slabs, common in patios and driveways, are large areas covered in a smooth layer of concrete. When the ground beneath the concrete shifts, the slab will sink and create an uneven surface. Sunken concrete is reparable, whether the entire slab sunk, or just one corner. Rather than calling in a professional to repair your patio or driveway, do it yourself for a fraction of the cost. All you need is supplies from your local hardware store and an hour of spare time.
Wash the concrete slab with a garden hose to remove dirt, gravel and debris.
Use a hammer and nails to build a frame around the concrete slab with four wooden boards. Ensure the height of the frame extends three inches above the slab's surface. The length of two of the boards must be six inches longer than the sides of the concrete slab, while the other two must match the sides of the concrete slab. This allows you to nail them flush against one another.
Mix concrete in a 5-gallon bucket per the manufacturer's instructions. If the slab you are working with is larger than 4-feet-by-4-feet, you will need a larger container or multiple buckets. Most bags of concrete mixture state how large of a surface it will cover.
Pour the concrete onto the slab and allow it to settle naturally. The majority of the mixture will pool over the sunken area of the slab.
Level the area with a wood float after the concrete mixture has settled. Begin working on one side and run the tool over the concrete to create a flat, smooth surface.
Allow the concrete to dry for the time specified by the manufacturer once its surface is smooth and flat.
If the area is still uneven after the first layer of concrete dries, repeat the process. If the concrete slab is damaged severely from sinking, double the amount of concrete mixture you use. This allows for enough mixture to fill the cracks and level the area.