Slab Leak or Soil Washout? Why a Floor May Be Sinking in Florida

A floor that feels lower near a doorway or develops a new crack can leave you wondering what is happening beneath your Florida home. You might hear the terms slab leak, soil washout, or foundation settlement. They can be related, but they are not the same problem.

A hidden pipe leak can leave floors damp. Moving water can carry soil away and create a space beneath concrete. A slab or foundation can also settle because its support was poorly compacted or has changed over time. Some flooring problems have nothing to do with movement of the concrete underneath.

APD Foundation Repair helps property owners evaluate sinking floors, foundation movement, and water-related support problems. This guide explains what the clues may mean, who should investigate them, and why the correct repair depends on the cause. For the broader picture, see our Florida foundation settlement guide.

Start here: A damp floor does not prove a slab leak, and a low floor does not prove soil washout. Look at the plumbing, the water paths, and the structure before choosing a repair.

First, What Part of the Floor Is Actually Moving?

Many Florida homes have a concrete slab-on-grade. That means concrete rests on prepared ground, but the foundation may include thicker footings or other structural parts that carry the building. Those parts do not always behave the same way as the thinner floor slab.

A sunken tile or vinyl surface may result from damaged flooring, a failed underlayment, or uneven concrete. A cracked slab may have lost support beneath one area. If walls, doors, windows, and the slab are changing together, the concern may involve the building foundation rather than a finish problem alone.

This distinction changes the repair. A suitable concrete panel may be leveled; a load-bearing foundation problem could call for a different structural design. APD's foundation repair services address building-support concerns, while the concrete repair service covers appropriate concrete work.

What Is a Slab Leak?

A slab leak is a plumbing leak beneath or within a concrete slab. It may involve a pressurized water-supply pipe. A damaged drain or sewer pipe can also leak beneath the slab, but it may behave differently because wastewater lines are generally not pressurized in the same way.

Water from either type of pipe can reach the soil or building materials. Depending on the amount and path of water, it may cause damp flooring, damaged finishes, or changes to the ground below the slab. But a plumbing leak does not automatically cause foundation settlement.

Clues That Make a Water-Supply Leak Worth Checking

·       An unexplained increase in your water bill or a meter that records use when all fixtures and irrigation are off.

·       A warm floor area where a hot-water line could run, especially with other signs of moisture.

·       Persistent dampness, loose flooring, or a musty smell that does not match recent weather.

None of these signs locates a leak. A leaking toilet, irrigation line, or visible plumbing fitting can also change a water bill. A warm spot may have another explanation, and moisture can enter from the outdoors.

Important: A home water meter can help flag unwanted use on a metered supply line. It cannot prove the leak is under the slab, and it may not detect a leaking drain pipe.

What Is Soil Washout Beneath a Slab?

Soil washout happens when moving water carries soil particles away from a location that needs support. The resulting loss of soil can leave a void under concrete or allow nearby material to shift. This may happen around a driveway, pool deck, patio, or foundation area where water can escape through an open edge or a drainage path.

Possible water sources include a broken drain, poorly directed roof runoff, a failed underground downspout, irrigation, or a plumbing leak. The important issue is not simply that the sand became wet. Water must have a way to transport material or otherwise change the supporting ground.

Florida properties can have very different fill, groundwater, and soil conditions. An area of sand does not automatically wash out during every storm. Our guide to sandy-soil stabilization and article on poorly compacted fill beneath homes explain two related, but separate, support problems.

Signs That Deserve a Closer Look

·       A new or widening gap beside a slab edge, downspout outlet, or drainage feature.

·       Soil visibly disappearing, sinking, or collecting downhill after rain.

·       A concrete panel that moves, slopes, or cracks near an area where water concentrates.

A hollow sound can be a reason to investigate, but it does not confirm a void. Tile installation and other floor layers can also sound hollow. Likewise, a dip after a storm does not establish that rain caused it.

Slab Leak vs. Soil Washout: Which Clues Matter?

If the Clues Point Toward Plumbing

Unexplained metered water use, repeated moisture in the same room, or the sound of running water when fixtures are off may justify a plumber or leak-detection specialist. Some supply leaks are hidden; a drain leak may be noticed mainly after plumbing fixtures are used.

If the Clues Point Toward Erosion or Lost Support

Visible soil loss near a slab edge, water discharging toward the building, or a localized drop in outdoor concrete may suggest a drainage or soil-support problem. But you still need to determine where water is coming from and whether the affected concrete is structural.

If Both Types of Clues Appear

The causes may overlap. A broken underground pipe could leak and carry soil away. A stormwater path could enter a plumbing trench that was not properly restored. Fixing only the wet flooring or only the low spot may leave the source untouched.

Key distinction: A leak describes where water is escaping. Washout describes what flowing water may be doing to the soil. One property can have both.

Five Safe Checks You Can Make Before Calling a Contractor

·       Document the change. Photograph the floor, cracks, adjacent walls, and outdoor slab edges. Note the date and whether a change is getting worse.

·       Review your water use. If it is safe and practical, compare water-meter readings during a period when no water is being used. The EPA's home leak-check guidance explains this approach. A change suggests unintended water use, not its location.

·       Look for other plumbing issues. Check visible fixtures, toilets, irrigation, and accessible supply connections before assuming a pipe beneath the floor failed.

·       Observe outdoor water paths. From a safe location, note overflowing gutters, downspouts aimed at the house, standing water, or soil disappearing near concrete.

·       Notice connected symptoms. Sticking doors, new wall gaps, and changes in more than one room are useful details for a foundation evaluation.

Avoid digging beside the foundation, probing beneath the slab, using a jack, or injecting filler yourself. Do not enter a visibly unstable area or walk onto a slab that appears to be collapsing.

Safety first: If a slab or ground surface is dropping quickly, a deep hole is opening, or the building appears unsafe, keep people away and seek urgent local assistance rather than continuing home checks.

How Professionals Separate Plumbing Problems From Structural Movement

Step 1: Identify and Control a Suspected Pipe Leak

A licensed plumber or qualified leak-detection specialist may use pressure tests, acoustic equipment, line tracing, or other suitable methods. The exact test depends on whether the suspected pipe carries supply water or drains. If a damaging leak is confirmed, the water source generally needs attention before finishes or support are restored.

Step 2: Examine the Slab, Foundation, and Drainage

A foundation evaluation looks for a pattern rather than judging one crack. Measurements may show whether movement is localized to a floor panel or extends to load-bearing parts of the home. The inspection may also consider downspouts, grading, plumbing work, drainage structures, and signs of disturbed soil.

When movement is suspected, an appropriate structural or geotechnical professional may be needed to evaluate loads, subsurface conditions, and the repair design. If you receive measurements or recommendations, our guide to reading a foundation engineer report can help you understand the terminology.

Step 3: Match the Repair to the Finding

The repair plan should identify what needs to stop, what needs support, and what result is realistic. APD Foundation Repair can discuss the foundation and drainage aspects after the underlying concerns are assessed. For the full decision process, see how foundation settlement is repaired.

Which Repairs May Be Appropriate?

When a Pipe Is Leaking

The first job is to repair or reroute the damaged plumbing as appropriate. Then the affected materials must be assessed for drying, moisture damage, and restoration. The EPA's guide to moisture control stresses that the water source needs correction, not just cleanup of the visible damage.

A plumbing repair alone may be sufficient if no meaningful loss of slab support or structural damage occurred. Do not assume that every pipe leak requires injection, leveling, or pier installation.

When Water Is Carrying Away Soil

The water path must be evaluated and corrected. That could involve a downspout outlet, drainage line, surface grading, or another site-specific problem. APD's drainage solutions are relevant when poor water routing contributes to the condition.

If a nonstructural concrete panel has lost support, a qualified contractor may consider void filling, controlled lifting, replacement, or another suitable repair. Those options depend on the slab, the size and cause of the unsupported area, and whether the water path has been corrected.

When the Building Foundation Has Settled

If the problem affects the home's structural foundation, surface concrete leveling may not solve it. An appropriate repair may involve designed support, which could include underpinning or other stabilization work. Explore foundation stabilization methods, our foundation pier comparison, and APD's underpinning services for the distinctions.

A foundation repair may aim to stabilize further movement. Raising a settled area is a separate question and may not be possible or advisable. If underpinning is proposed, compare the included scope rather than relying on a price per pier; see our foundation underpinning cost guide.

Before the quote: Ask whether the proposal fixes a water source, replaces missing soil support, stabilizes a structural foundation, or combines these tasks. They are different scopes of work.

Could the Problem Be Something Other Than a Leak or Washout?

Yes. Poorly compacted fill can settle without a continuing water leak. Movement may also be mistaken for foundation heave, which involves upward movement in some situations. Our heave versus settlement explanation compares those patterns.

Florida also has areas where ground depressions raise concerns about sinkholes. A low spot is not proof of sinkhole activity. The Florida Geological Survey's sinkhole FAQ describes several look-alike causes, including broken underground pipes, buried debris, and poorly compacted soils. A suspected sinkhole requires an appropriate professional assessment.

Two Common Situations That Call for Different First Steps

Example: A Damp Floor and a Rising Water Bill

A homeowner notices loose flooring near the kitchen and higher water use, even though there has been little recent rain. A plumbing evaluation should come early. If the pipe is repaired and the slab remains sound, there may be no foundation-stabilization project to perform.

Example: A Dropping Patio Edge After Repeated Runoff

A patio or walk has a growing gap beside it, and water from a downspout flows toward that location. A drainage and concrete-support evaluation is more relevant than assuming an under-slab supply leak. The correct repair may combine water diversion with the appropriate treatment of unsupported concrete.

For a more focused explanation of a suspected unsupported slab, see our guide to voids beneath concrete. These examples are illustrations, not diagnoses of an individual property.

What Affects Repair Cost and Timing?

There is no responsible single price for a "sinking floor" without knowing what has moved. A small plumbing repair, large-scale moisture restoration, drainage correction, concrete leveling, and engineered underpinning involve different crews, materials, and work.

Ask whether plumbing work, testing, engineering, permits, drainage, concrete restoration, flooring replacement, and post-repair measurements are included or excluded. A quote that covers only one part of the problem may not be comparable to a quote addressing several causes.

When to Call APD Foundation Repair

If you see new floor cracks, a low area that appears to be growing, gaps beside the slab, or other signs of possible foundation settlement, APD Foundation Repair can evaluate the foundation-related symptoms and discuss the next step. Plumbing diagnosis and repair should be handled by the appropriate qualified plumbing professional.

The purpose of an evaluation is not to choose the most invasive repair. It is to understand what has changed, what is carrying the load, and whether the cause is still active. If you are unsure what is happening beneath your home, contact APD Foundation Repair about a foundation or drainage evaluation.

Takeaway: Fix the source before restoring the surface. A dry floor, a filled void, and a stable foundation are different results, and your repair plan should explain which ones it addresses.

Frequently Asked Questions About Sinking Floors in Florida

Can a Slab Leak Cause a Floor to Sink?

It can contribute if water changes or removes supporting soil, but many plumbing leaks cause moisture damage without significant structural movement. A professional assessment is needed to establish the cause.

Will a Water Meter Tell Me Whether the Leak Is Under My Slab?

No. A meter can suggest unwanted water use when no fixtures are running, but it does not locate the leak. Drain leaks may not be detected by this method.

Can Rain Make a Concrete Floor Sink Overnight?

A sudden change after rain deserves attention, but timing alone is not proof of soil washout. Existing weak support, drainage paths, and other causes must be checked.

Does a Hollow Sound Mean There Is a Void Under the Concrete?

Not necessarily. Hollow sounds can also come from tile or flooring layers. The slab and supporting conditions need to be evaluated before choosing a repair.

Is Soil Washout the Same as a Sinkhole?

No. Washout refers to transported soil. A sinkhole is a particular ground feature associated with subsurface processes. Florida ground depressions can have multiple causes and require careful identification.

Will Leveling the Concrete Prevent Future Settlement?

Not by itself. A repair must account for why the concrete moved, whether water or soil loss continues, and whether a structural foundation is involved. No single leveling method is appropriate for every site.