Lift A Partial Concrete Patio Slab: Diy Guide

Uneven concrete slabs are a common problem with various causes, from soil sinking or shifting to rainwater pooling. Whatever the cause, it's important to address the issue promptly to restore functionality and safety. While getting a replacement slab may be the first solution that comes to mind, there are other ways to deal with this problem, such as concrete lifting or mud jacking. This involves drilling holes into the slab and injecting it with a mixture of water, soil, sand, and cement or polyurethane foam. This process is less invasive and more cost-effective than replacing the entire slab. However, it's important to hire a professional for this job, as it requires specialised equipment and expertise.

Characteristics of Lifting a Partial Concrete Patio Slab

Identify the cause of the sinking

Before attempting to lift and level a sunken concrete patio slab, it is important to identify the cause of the sinking to prevent it from happening again. Concrete is heavy, and the soil beneath it must be able to support its weight. If the soil is unable to bear the load, the slab will sink or crack.

Soil Compaction

One of the most common reasons for concrete slabs to sink is poor soil compaction. When the soil underneath a concrete slab is not properly compacted before the slab is poured, it can settle and leave voids beneath the slab, causing it to sink or crack. Soil compaction is especially important if you live in an area with sandy or loose soil, such as Dallas or Fort Worth.

Water Drainage

Water drainage problems can also lead to concrete slabs sinking. Poor water drainage can cause soil to become saturated, weakening its structure and reducing its ability to support the slab. This is often caused by improper ground slope, which allows water to accumulate around the slab. Puddling water can also seep into the edges of the slab, causing soil contraction and expansion.

Soil Washout

Sudden soil washout can occur due to heavy rain or flooding, causing the soil underneath the slab to be washed away and creating voids that the slab may sink into. Tree roots can also contribute to soil washout and damage concrete slabs, causing them to crack or sink.

Underground Critters

Underground animals such as moles, chipmunks, and rodents can burrow beneath a concrete slab, causing it to sink or crack.

Substandard Craftsmanship

Substandard craftsmanship during the installation of a concrete slab can also lead to settling, cracking, and sinking. This includes improper backfilling of the slab's edges with soft soil and loose aggregates.

Use a slab jacking pump

Using a slab jacking pump to lift a partial concrete patio slab is a quick and hassle-free method of stabilising your patio. This process is also known as concrete leveling and can be done by following the steps outlined below.

Step 1: Drill Dime-Sized Holes

Begin by drilling dime-sized holes into the sunken slabs. These holes should be placed around three to eight feet apart but should not be closer than one foot from the slab's edge. The thicker the concrete, the farther apart these holes can be. These holes serve as entryways for the lifting solution, so they must be placed at approximately equal distances from one another.

Step 2: Install the Delivery Port

Once the holes are drilled, install tapered delivery ports into them. These ports will be connected to the application gun, which will transport the lifting material to the voids underneath the sunken slab.

Step 3: Pump the Lifting Material

With the delivery ports in place, it's time to start pumping the lifting material. Begin at the lowest part of the recessed surface and fill the void in the substrate. Polyurethane foam or polyfoam is a popular choice for lifting material due to its fast-acting nature and ability to stabilise concrete quickly. Traditional concrete leveling methods use a mixture of water, soil, sand, and cement in a process called mudjacking.

Step 4: Monitor the Raising

Concrete leveling requires close monitoring. Use incremental injections, as polyurethane foam expands and slowly compacts the soil underneath, pushing the slabs upward. Alternate the injection points to balance the pressure on the substrate and ensure the slabs rise to a level position. Even and steady lifting helps prevent cracking during the process.

Step 5: Patch the Holes

Once you've achieved the desired elevation, it's time to close the holes. Remove the delivery ports and seal the holes using a mortar mix. Apply the mixture carefully for a smooth and seamless finish.

By following these steps and using a slab jacking pump, you can effectively lift a partial concrete patio slab and restore it to its original level.

Drill dime-sized holes

Drilling dime-sized holes into a concrete patio slab is a crucial step in the concrete lifting process. This process is also known as concrete leveling, and it's a quick and hassle-free method of stabilising and raising a sunken slab.

The first step is to identify the areas of the patio that have sunk the most. These areas will require the most lift, so it's important to drill the holes in these sections. The holes provide a clear access point for injecting the leveling material.

When drilling dime-sized holes, it's important to space them evenly. The holes should be around three to eight feet apart but at least one foot from the slab's edge. The thicker the concrete, the farther apart the holes can be. However, it's crucial that the holes are approximately equidistant from one another, as they will serve as the entryway for the lifting solution.

To drill the holes, you'll need the right tools and safety equipment. Experts recommend using a hammer drill with masonry drill bits or concrete diamond point screws. Hammer drills are designed to hammer while rotating, effectively drilling into concrete. When drilling, always wear eye and hearing protection, work gloves, and a dust mask. The silica dust produced by drilling concrete can be hazardous to your health if inhaled, so it's important to take the necessary precautions.

Install tapered delivery ports

After drilling the dime-sized holes, the next step is to install the tapered delivery ports. These are crucial components in the concrete lifting process as they serve as the conduit for transporting the lifting material to the targeted areas.

The tapered delivery ports are designed to be inserted into the drilled holes. Their tapered shape ensures a snug fit, creating a stable channel for the injection process. The size of the delivery ports corresponds to the size of the holes, typically ranging from dime-sized to 5/8-inch in diameter.

Once the delivery ports are in place, they are connected to the application gun or injection gun. This gun acts as the delivery system for the lifting material, which can be polyurethane foam, a grout mixture, or a slurry mix, depending on the chosen lifting method.

The tapered design of the delivery ports plays a vital role in guiding the lifting material accurately and ensuring controlled delivery. This precision is essential to achieve successful and uniform lifting of the concrete slab.

It is important to ensure that the delivery ports are securely attached to the application gun to prevent any leakage or misdirection of the lifting material. The connection between the port and the gun forms a sealed passageway for the material to flow through.

With the delivery ports and application gun assembled, the stage is set for the next critical step—pumping the lifting material.

Pump the lifting material

Now that the delivery ports are in place, it's time to start pumping the lifting material. This is the stage where you'll fill the void in the substrate and raise your patio to its original level. For the best results, start at the lowest part of the sunken surface and work your way up.

The type of lifting material you use will depend on the method you've chosen for your project. If you're using the traditional mudjacking method, you'll need a hydraulic grout pump to inject your mixture. You can either buy a pre-made bagged compound or create your own mixture of soil, sand, and water. You can also add Portland cement to increase the strength of your mixture, but be aware that this will begin to harden as soon as water is added, so you'll need to work quickly.

Make sure your mixture is thin enough to pass through the pump and hose but thick enough to build up the pressure needed to lift the slab. Set up your hydraulic pump and add the mixture to the hopper, ensuring all connections are tight to maintain pressure and prevent leaks. Place the end of the hose into one of the drill holes and slowly pump in the material. Remember, you can always add more, but you can't remove it if you pump in too much.

If you're using the faster and more modern method of foam jacking, you'll be injecting polyurethane foam under pressure to fill the voids. This method requires smaller holes and fewer injections, and the fast-acting material can fill voids and stabilize concrete within seconds. It's also lighter than traditional mudjacking mixtures, making it less likely to cause further sinking.

Regardless of the method you choose, it's important to monitor the raising process closely. Concrete leveling is best done with incremental injections, especially when using polyurethane foam, as it expands and slowly compacts the soil underneath. Keep a close eye on the vertical movement and adjust your injection points as needed to ensure even and steady lifting. This will help prevent cracking and provide a smooth, level finish.

Frequently asked questions