When this service makes sense
Voids beneath slabs reduce support and can contribute to rocking, cracking and settlement. Injection materials can fill hidden spaces beneath existing concrete. The first step is determining whether the slab is still strong enough to preserve and whether the movement is primarily settlement rather than upward heave.
What affects price?
Contractors look at the number and size of slabs, depth of the void beneath them, amount of elevation change, access for equipment, material choice, surface condition and minimum service charges. That is why two projects with the same visible square footage can price very differently.
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Common questions
How do you know there is a void under concrete?
Clues include hollow sounds, rocking slabs, settlement, erosion at slab edges or visible washout. Contractors may use probing or other evaluation methods.
Does void filling always lift the slab?
No. Material can be injected primarily for stabilization, or the injection can be controlled to produce lift when appropriate.
What causes voids under concrete?
Water erosion, poor initial compaction, broken drainage, soil shrinkage and loss of fill material are common causes.