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Much of the modern world is built on concrete slabs, yet modern concrete is guaranteed to last only 100 years under ideal conditions.

Unfortunately, the weather in Northeast Pennsylvania is less than ideal, especially during the wintertime when snow and rapid freeze-thaw cycles can significantly weaken concrete. 

Furthermore, warm seasons bring little relief as increased hydrostatic pressure from surrounding soil saturated with water can cause foundations, driveways, patios, and sidewalks to shift and settle.

Over time, this rapid movement of concrete and soil can lead to uneven surfaces, cracks, and fissures.

One of the most affordable and easiest ways to repair sunken or cracked concrete is to lift the slab from underneath using concrete leveling methods. 

However, the method you choose to lift a concrete slab will greatly affect its durability, among other factors. 

We’ll compare different concrete lifting methods in this blog and give you our opinion on the best method to lift a concrete slab based on our experience.  

Common Causes of Concrete Slab Settlement

First, it’s essential to determine the cause of concrete settlement or cracking to decide on the best strategy for future repairs. In extreme cases, concrete leveling may not even be advisable if the slab needs to be regraded or replaced entirely.

With that said, some of the most common causes of concrete slab settlement include:

• Soil Erosion: As water penetrates the soil underneath and surrounding the slab, it can slowly wear away at it, forming voids that can lead to concrete shifting or settling. 
• Poor Soil Compaction: Improperly compacted soil during construction can come back to bite you as it can cause soil to shift through natural pressures and settlement to occur. 
• Heavy Loads: Excessive weight, such as vehicles or heavy equipment, can put stress on a slab and cause it to sink.
• Freeze-Thaw Cycles: In colder climates like NEPA, water can seep under the slab, freeze, and expand, leading to movement and cracking.

In each of the cases listed above, concrete leveling is often available to lift and level the slab while stabilizing the soil surrounding it. With that in mind, let’s explore different concrete leveling methods to determine which is right for your situation. 

1. Polyurethane Foam Injection

Polyfoam is a new and innovative form of concrete leveling that is minimally invasive and long-lasting. Considered the best form of concrete lifting for basic settlement, polyfoam works by injecting a self-expanding foam underneath the slab to provide stability.

A contractor can measure the level at which the slab is lifted for perfect equilibrium using special tools. All that’s required is drilling two penny-sized holes, which are barely noticeable. Most importantly, polyfoam resists moisture and, under ideal conditions, can last up to 75 years or more. 

This method can be used for residential, commercial, and industrial applications.

Pros:

• Lightweight Material: Unlike mudjacking, polyurethane foam does not add significant weight to the soil.
• Long-Lasting Solution: The foam resists erosion and does not break down over time.
• Quick Cure Time: The foam hardens within minutes, allowing for fast project completion.

• Minimally Invasive: Installation only requires two penny-sized holes to be drilled. 

Cons:

• Higher Cost: Polyurethane injection is more expensive than mudjacking but more affordable than concrete piers or pilings.
• Requires Professional Expertise: This is not a DIY-friendly solution, as specialized equipment is needed.

2. Mudjacking (Slabjacking)

Mudjacking, also known as slabjacking, is an affordable alternative to polyjacking, though it does come with some concerns. 

In essence, mudjacking involves pumping a mixture of water, soil, sand, and cement under a concrete slab to raise it back into place. This method is typically used for driveways, patios, and sidewalks, but it does require large amounts of materials and larger holes dug in or around the slab to raise it.

The biggest drawback of mudjacking is its longevity. By most estimates, mudjacking only lasts 3-5 years before settling may occur once more. 

Pros:

• Cost-Effective: Mudjacking is generally cheaper than replacing the entire slab and other forms of concrete leveling.
• Quick Process: Most projects can be completed within a few hours, though cure times can take up to 48 hours.

Cons:

• Not a Permanent Solution: The material can erode very quickly, requiring repeat treatments.
• Heavy Material: The slurry mixture is heavy, which can contribute to further settling if the underlying soil is weak.
• Limited for Large Slabs: Not always suitable for lifting large or heavily loaded slabs.

• Invasive Installation: The heavy materials used in mudjacking can damage underground utilities if not properly installed.  

3. Concrete Piers or Pilings

Concrete piers or pilings are support structures that are installed beneath the slab to provide permanent structural support. These are often used in cases of significant foundation settlement and recommended for expensive projects that require long-lasting support.

Pros:

• Permanent Solution: Piers offer long-term stability and can handle heavy loads.
• Prevents Future Settlement: Addresses deep soil issues rather than just surface problems.
• Works for Large Structures: Suitable for lifting homes, garages, and other heavy structures.

Cons:

• Expensive: One of the most costly slab-lifting methods.
• Intrusive Installation: Requires significant excavation and disruption.
• Time-Consuming: Takes longer to complete compared to mudjacking or foam injection.

4. Grouting (Pressure Grouting)

How It Works

This method involves injecting a cement-based grout mixture under the slab to fill voids and raise it. Pressure grouting works similarly to mudjacking and polyjacking, but is designed to be a longer lasting/permanent solution. 

Pros:

• Stronger Than Mudjacking: The cement-based material is more durable than traditional mudjacking mixtures.
• Works for Deep Voids: Can address deeper soil issues effectively.
• Resists Erosion: Provides better longevity compared to basic mudjacking.

Cons:

• Higher Cost: More expensive than mudjacking and polyjacking.
• Can Be Messy: The grout mixture requires careful handling to avoid spills and excess waste.
• Not Ideal for Small Slabs: Best suited for large projects with significant voids.

Which Method is Right for You?

Choosing the best method to lift a concrete slab depends on several factors, including budget, severity of settlement, and long-term durability. Here’s a quick comparison:

Generally speaking, we caution anyone against mudjacking, as it provides a temporary bandaid for a problem that requires a longer-term solution. 

For simple projects, such as concrete patios, driveways, sidewalks, and even small foundation settling, polyjacking is your best bet. Not only does it offer long-term stability, but it’s very accurate and will create a truly level and unblemished slab once more. 

Depending on the cause of settlement, concrete piers or grouting may be more suitable for larger projects that require greater structural stability.

FAQs

What causes a concrete slab to sink?

Concrete slabs sink due to soil erosion, poor compaction, excessive moisture, or organic material decomposition beneath the slab, leading to voids and settlement.

What is polyurethane foam injection?

This method uses a lightweight, expanding polyurethane foam injected beneath the slab. The foam fills voids, stabilizes the soil, and lifts the concrete with minimal disruption. It cures quickly and provides long-term durability.

Will lifting the slab prevent future sinking?

Lifting a slab addresses the immediate issue, but long-term stability depends on fixing underlying causes like poor drainage or soil erosion. Some methods, like polyurethane foam, provide better long-term support than others.