Soil washout is the erosion of soil from beneath a concrete slab by moving water, which carries the supporting material away and leaves voids that let the slab sink.
In depth
Water is the number-one enemy of stable concrete. Heavy rain, poor drainage, leaking pipes, and downspouts dumping water near a slab all wash fine soil out from underneath, and water penetrating through surface cracks slowly erodes the base material below. The resulting voids remove support, and the slab settles or cracks into the empty space.
Because washout is a water problem, lasting repairs pair void filling with better water management, such as redirecting downspouts, improving grading, and sealing joints. The fill material itself must also resist water so it does not erode in turn.
How Acme applies it. Acme calls erosion one of the primary reasons concrete sinks, and its erosion-resistant foam turns to solid within minutes and will not wash away from water and moisture over time the way mudjacking slurry can.
Related terms: Under-Slab Void, Concrete Settlement, Grading & Drainage, Seawall Stabilization
Frequently asked questions
What causes soil washout under concrete?
Moving water from heavy rain, poor drainage, downspouts, or leaking pipes carries soil out from under the slab, and water seeping through cracks erodes the base material.
How do you stop soil washout from returning?
Fill the voids with erosion-resistant polyurethane and address the water source by redirecting downspouts, improving grading, and sealing joints and expansion gaps.