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How to Fill Voids Under Concrete

sinking concrete slab gap

Imagine walking on your concrete sidewalk or driveway, only to have it suddenly collapse beneath your feet. This alarming scenario is a reality for many homeowners with untreated concrete damage. 

This page explains how to prevent and repair concrete voids to ensure property safety and integrity.

What is a Concrete Void?

concrete gap tape measure

A concrete void is a space or gap beneath a concrete slab. These voids compromise structural stability and strength, leading to concrete cracks, uneven surfaces, and other structural issues.

What Causes Voids in Concrete?

Many factors contribute to concrete void formation. Common causes include:

  • Soil erosion
  • Expansive soil
  • Freeze-thaw cycles
  • Improper subgrade compaction 
  • Water infiltration and plumbing leaks
  • Faulty drainage systems

Addressing the causes of concrete damage prevents future problems and extensive repairs.

How to Repair Concrete Voids

Repairing concrete voids before they worsen is crucial for maintaining structural integrity. Here are three standard repair options:

mudjacking slurry


Mudjacking involves pumping a heavy slurry mixture beneath the concrete slab to lift it to a level position. This method offers temporary relief, as it does not address the underlying causes of concrete damage.

polyrenewal concrete lifting foam underground soil

Polyurethane Foam Injection

PolyRenewal™ involves applying a lightweight, eco-friendly polyurethane foam injection to the compromised concrete areas. The foam expands, fills voids, and lifts the concrete back into place. PolyRenewal™ offers a permanent solution, addressing underlying issues causing voice. 

crew member concrete bag wheel barrow

Slab Replacement

In cases where the concrete is too damaged, slab replacement might be necessary. This method involves removing the old slab and pouring a new one into its place, ensuring a solid and durable foundation.

Repairing concrete voids is complex and requires professional expertise. DIY repairs often lead to extensive damage, safety risks, and higher costs. Contacting a concrete professional is always the best option for ensuring a safe and effective repair. 

How to Prevent Concrete Damage

Preventative measures save homeowners time and money. These include:

sealing concrete crack with epoxy
  • Installing drainage systems to direct water away from concrete
  • Promptly repairing plumbing and irrigation leaks
  • Sealing concrete to prevent water seepage into cracks
  • Avoiding excessive weight loads on concrete slabs
  • Implementing proper landscaping to redirect water
  • Conducting regular foundation inspections and maintenance  

Professional Concrete Repair Ensures Property Safety

Groundworks work truck

Concrete voids are common, but they don’t have to jeopardize your home. These empty spaces can cause sinking, cracks, and foundation settlement, which can jeopardize safety. Prevent these occurrences with professional concrete lifting and repair.

Groundworks teams can assess concrete damage, diagnose the underlying problems, and provide customized, permanent repair options.

Contact us for a free inspection and no-obligation repair estimate today.

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    Shaye Glisson

    Shaye Glisson

    Shaye is an SEO Content Writer for Groundworks with over twelve years of experience creating helpful content across various industries, including home services and retail. She is a Gulf Coast native and writes from her firsthand knowledge of the area's hurricane and flood impacts on the local community. In her free time, Shaye enjoys exploring the local food and music scenes.