How do I know if my concrete slab is bad?

Author: Madisyn Koch  |  Last update: Wednesday, September 10, 2025

A common sign of concrete failure is cracks. A few small hairline cracks that aren't actively growing and spreading are not necessarily a big problem. But larger, growing cracks are an issue that can affect your home's water drainage, affect the aesthetics, and damage your concrete's structural integrity.

How can you tell if a concrete slab is bad?

You can tell if a slab is cracked in a few ways. One way is to look at the surface of the slab. If you see any cracks, then the slab is probably cracked. Another way to tell if a slab is cracked is to tap on the surface of the slab. If you hear a hollow sound, then the slab is probably cracked.

What does failed concrete look like?

The most common signs of concrete failure are uneven surfaces, cracks, and breaks.

When should I be worried about a slab foundation?

Visible Cracks: Large or expanding cracks in the slab, floors, walls, or ceiling may indicate significant structural issues. If you can fit a coin into the crack, it requires immediate attention. Uneven Floors: Floors that are no longer level or appear to be sinking can signal foundation problems.

What is the life expectancy of a concrete slab?

Generally, for large infrastructures, the lifespan of modern concrete is about 100 years if properly maintained.

4 Key Signs That Your House Has Foundation Issues

When should I replace my concrete slab?

While concrete is much more resilient than other surfaces, it still has an “expiration” date. If your surface is facing 20-25 years of use, it is probably time to replace the concrete. Exterior concrete faces more elements than interior, so adjust your concrete age accordingly.

How long will rebar last in concrete?

BFRP Rebar does not rust, it has the same thermal expansion coefficient as concrete, it is resistant to water, alkaline, and ultraviolet radiation, therefore it can have a life expectancy of more than 100 years!

How do I know if my concrete foundation is bad?

4 Major Signs of a Bad Foundation
  1. #1) Wall Cracks and Fractures. ...
  2. #2) Foundation Settling or Sinking. ...
  3. #3) Foundation Upheaval. ...
  4. #4) Noticeable Interior Separation.

How often should you water a slab foundation?

You might expect to water your foundation for 15 to 20 minutes twice daily, three to five days per week in the peak summer heat. In drought conditions, you may need to water for up to 45 minutes every day. During winter months, you might expect to use less water due to cooler temperatures and increased soil moisture.

Why is my concrete floor bulging?

Moisture damage is one of the primary causes of a floor bulging upwards, often resulting from high humidity levels, leaks, or inadequate moisture control.

How do you test a concrete slab?

Methods for Testing Compressive Strength of Concrete
  1. Rebound Hammer or Schmidt Hammer (ASTM C805) ...
  2. Penetration Resistance Test (ASTM C803) ...
  3. Ultrasonic Pulse Velocity (ASTM C597) ...
  4. Pullout Test (ASTM C900) ...
  5. Drilled Core (ASTM C42) ...
  6. Cast-in-place Cylinders (ASTM C873) ...
  7. Wireless Maturity Sensors (ASTM C1074)

How do you fix a bad concrete slab?

Repair Concrete Walkways and Steps
  1. Step 1: Remove the Loose Concrete. Remove any damaged or crumbling concrete. ...
  2. Step 2: Clean the Concrete. Clean the area in and around the damage with a wire brush and broom. ...
  3. Step 3: Position the Concrete Patch Form. ...
  4. Step 4: Mix the Concrete Crack Sealer. ...
  5. Step 5: Smooth the Concrete Patch.

How to tell if cement is bad?

RUB TEST: In this test, one must take a little cement between their fingers and rub it. If the texture feels smooth, it's considered good quality cement. If the texture is rough, it is likely adulterated with sand.

How do you inspect a concrete slab?

These factors include:
  1. Checking that the concrete slab is level.
  2. Checking for the absence of surface cracks.
  3. Confirming that the concrete slab is even and has been compacted properly.
  4. Examining the slab for any discoloration.
  5. Identifying signs of defects, such as spalling or honeycombing.

Can you pour new concrete over old concrete slab?

You can pour concrete on top of an existing slab as long as it's still in reasonably good condition and structurally sound. This means the concrete should be free of cracks, buckling, and breaks. If you notice any small cracks or minor issues, it's in your best interest to repair them before you pour the new concrete.

What does slab leak look like?

Here are some slab leak symptoms to look out for: A raised “dome,” water stains, or warm spots on the floor. Foundation heaving caused by shifting or swelling soil. An increase in water or heating bills, as well as low water pressure.

When should I worry about slab foundation?

Look for cracks in the foundation, walls, or floors of your home. Also, check for uneven floors or doors that do not close properly. Examine the exterior of your home for any signs of sinking or settling, as well as water damage and mold, which can all be indicators of potential foundation issues.

How often should you water a concrete slab?

Most specialists recommend watering the slab 5 to 10 times per day for the first seven days. Moist-cured concrete can be up to 50% stronger than dry-cured concrete.

How to tell if your foundation needs watering?

Signs the Soil Around Your Foundation is Too Dry

Visual indicators include large cracks in your yard, and, in extreme instances, soil visibly pulling away from your home's foundation (see pictures below). Soil pulling away indicates the foundation needs watering. Large cracks in the yard indicate the soil is too dry.

What is the lifespan of a concrete slab?

How Long Does Concrete Last on Average? Concrete lasts around 50 to 100 years, according to the Portland Cement Association, which focuses on cement-related policy, education, and research. Of course, this is quite the range, but concrete life span depends on numerous factors.

Does homeowners insurance cover foundation problems?

Homeowners insurance generally pays for foundation repairs that result from covered events. However, if the cause of the damage isn't covered in your policy, repairs probably won't be either.

How do you tell the difference between settling and foundation problems?

Vertical cracks are often less concerning and may result from normal settling. Horizontal or diagonal cracks, especially those wider than 1/8 inch, may indicate more serious problems. Multiple cracks or those that form a pattern (like stair-step cracks in brick walls) often signal foundation issues.

Can you put too much rebar in a slab?

There are numerous issues that arise as a result of using excessive reinforcement. The following are some of the most frequently encountered: Tie wire and other detritus on the outskirts. Without steel corrosion, there is cracking that mirrors the main rebars.

Can I still use rusted rebar in concrete?

A.: Section 12 of ASTM A 615-96a, "Standard Specification for Deformed and Plain Billet Steel Bars for Concrete Reinforcement," says that rust shall not be cause for rejection provided the weight, dimensions, cross-sectional area, and tensile properties of a hand-wire-brushed test specimen aren't less than the ASTM ...

What is the lifespan of a post tension slab?

Conventional concrete & rebar foundations last about 20-30 years before failure begins to occur. Post-tension slabs are lasting about 15-20 years and are failing at a much higher rate.

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