Helpful Ways on How To Seal, Fill & Fix Cracks in Garage Floor

First things first: Are cracks in the garage floor normal? Absolutely. Concrete is a fickle beast. It shrinks, expands, and generally throws tantrums as it ages. Most cracks are cosmetic and just part of the concrete’s personality. But some cracks say, “Hey, pay attention to me.”

Understand Garage Floor Cracks

Garage floors take a beating. They support your vehicles. Temperature changes hit them year-round. They endure extra water. Then there are the occasional oil spills and the dropped toolbox. Over time, cracks appear. Some are harmless and purely cosmetic. Other cracks could indicate a deeper issue. You may have foundation problems or soil issues.

Know the difference between a simple surface crack and one that signals a potential foundation problem. A small crack might not require much attention beyond a quick DIY fix. But if you notice widening cracks, uneven surfaces, or water intrusion on your garage floor.

Follow us while we break down:

• When to worry about cracks in your garage floor.
• How to properly fill and seal garage cracks.
• When foundation repair might be necessary.

We’ll also provide tips, recommendations, and steps to take before and after foundation work. Use it all and take care of your garage. Let’s dive in.

When to Worry About Garage Floor Cracks

Here’s how to tell if your cracks are just cosmetic or if they’re whispering, “Call a pro, buddy.”

Are Garage Floor Cracks Normal?

No-Big-Deal Cracks:

• Hairline cracks (less than 1/8″ wide) are purely cosmetic. No stress.
• Surface cracks: If they don’t go deep and don’t widen over time, they are a sign of a gracefully aging garage.
• Spiderweb cracks: Looks like a web, but doesn’t cause tripping hazards? Just ignore ’em or seal ’em for good measure.

Serious, Call-the-Experts Cracks:

• Wide cracks (wider than 1/4 inch): Could mean movement under your slab.
• Uneven cracks: If one side of the crack is higher than the other, that’s called “differential settling,” which could mean foundation issues.
• Expanding cracks: If you fill it, and it keeps growing like a bad habit, something is shifting underneath.
• Water intrusion: If you see moisture leaking or pooling, your slab might be cracking due to hydrostatic pressure.

Common Crack Types & What They Mean

When Is Foundation Repair Needed for a Cracked Garage Floor?

If your cracks are:

• Growing despite repairs
• Making your garage floor uneven
• Letting water in
• Accompanied by sticking doors or cracks in walls

Then, it’s time to bring in a foundation repair contractor.

DIY Fixes Before & After Foundation Repair

Knowing when to DIY and when to call a foundation repair contractor. Understand when to fix cracks in the garage floor before and after foundation repairs. It improves long-term results.

• Before repairs, focus on prevention rather than cosmetic fixes. Filling cracks beforehand is pointless since repairs may shift the slab. Instead, address potential causes of movement. Fix drainage issues. Direct water away from your foundation. Regrade your yard if needed.
• After repairs, let the concrete stabilize for a few weeks. Then, make cosmetic fixes. Use a flexible sealant like epoxy or polyurethane to fill the remaining cracks and prevent future widening. Seal the entire floor. It adds extra protection against moisture, stains, and wear.

Extend the life of the garage floor and protect your investment. It means doing three things. Have proper drainage. Do crack repair. Seal repaired cracks.

DIY Crack Fixing – What You Can Handle Yourself

• Follow the product instructions. Use a putty knife to smooth things over.
• Let it dry completely before walking or driving on it.

• Hairline Cracks: Liquid crack sealers like Quikrete Concrete Crack Seal work well. Just pour it in and smooth it out.
• Larger (But Still Manageable) Cracks: Use an epoxy-based filler or polyurethane sealant for better flexibility.
• Wide, Deep Cracks: Before applying filler, you’ll need a backer rod (a foam insert) to prevent sinking.

• If you want to go the extra mile, apply a concrete sealer after the repair to protect against future moisture and wear.

• Follow the product instructions. Use a putty knife to smooth things over.
• Let it dry completely before walking or driving on it.

Is Filling Cracks the Same as Sealing Them?

Not exactly! People use the words interchangeably. Filling Cracks and Sealing Cracks are similar but different. Each solves a different problem.

• Fill cracks with epoxy, polyurethane, or a concrete patch. What does that do? Fillers close gaps in the concrete. You help restore the floor’s integrity. Nothing will sneak in or under the floor after you have filled the gap. No crack means no creepy crawlers or water leaks. Crack fillers are usually rigid or semi-flexible. They bond with the concrete, stopping further damage.
• Seal cracks by adding a protective coating over the surface. It protects the form from moisture and chemicals. It also protects the floor from wear and tear. Sealers can be clear or tinted and provide a water-resistant barrier. Some sealers penetrate deep into the concrete. That strengthens it. Other sealants add a surface-level protective layer.

When Should You Fill vs. Seal?

• Is your crack wider than a hairline (1/8 inch or more)? If so, it needs filling before sealing.
• Does the floor have minor cracks, but is still in good shape? Seal it with a concrete sealer. That helps prevent future damage.
• For best results, fill the cracks first. Then apply a sealer over the entire garage floor. You give your floor added protection.

Are the cracks large or growing? Are they causing uneven surfaces? Make sure to check if it is more than surface damage. It could be a foundation issue. Arch Foundation Repair can assess your garage floor and provide a free foundation quote. 

Does Garage Floor Epoxy Fill Cracks?

Not really—garage floor epoxy is not designed to fill cracks. While it does create a smooth, protective coating over concrete, it does not properly seal or repair cracks on its own. 

Why Epoxy Alone Won’t Work for Cracks

• Epoxy is a surface coating, not a filler – It adheres to the top of the concrete but doesn’t fill deep cracks or bond separated sections together.
• Cracks will still be visible – If you apply epoxy over unfilled cracks, they can show through the coating and may even cause the epoxy to crack later.
• Epoxy is rigid – It doesn’t flex with concrete movement, so if a crack expands over time, the epoxy can split.

How to Fill Cracks Before Epoxy Coating

For a seamless epoxy floor, fill and repair cracks first:

1. Clean Cracks: Use a wire brush or shop vac. Clean out dirt, dust, and debris.
2. Fill Cracks :
   • Flexible Polyurethane Sealant: Use on small to medium cracks (1/8″ to 1/4″). Remaining flexible, it allows for slight slab movement without cracking again. Best for preventing water from leaking in. Results offer long-term durability.
   • Epoxy Crack Filler: Best for wider cracks (1/4″ and up) that need strong bonding. Epoxy hardens into a rigid, high-strength repair but doesn’t flex much, so it’s better for stable areas rather than shifting slabs.
   • Concrete Patch: Good for shallow surface cracks or spalling (flaking concrete). It smooths over damaged areas but isn’t ideal for deep or expanding cracks.
3. Let it Cure Completely: Follow the product’s drying time instructions.
4. Sand Smooth: If necessary, lightly sand the area for a level surface before applying epoxy.
5. Finish with Epoxy Coating: Coat the floor with epoxy for a clean, durable finish.

Best Crack Fillers for Epoxy Prep

So, if you’re planning to epoxy your garage floor, fill the cracks first. Otherwise, they’ll show up later and possibly cause coating failures. 

Best Crack-Filling Products for Garage Floors

Best Garage Floor Sealing Products

Final Thoughts on Cracks in Your Garage Floor Foundation

Cracks in garage floors are common. Some can be left alone. Others need attention. Hairline cracks are often cosmetic and easy to fix. You can fix these cracks yourself.

On the other hand, wide, uneven, or expanding cracks may indicate foundation issues. Before doing anything, bring in a foundation repair company. They can let you know if you need foundation work done.

Use high-quality fillers and flexible sealants to prevent further damage from minor cracks. Avoid cheap fillers that degrade quickly, and if cracks keep reappearing, monitor their growth and consult a foundation repair company.

Stay proactive—seal small cracks early, maintain proper drainage to reduce soil movement, and watch for signs of foundation shifting. Addressing minor issues now can prevent costly foundation repairs down the road. 

Garage Floor Foundation Repair

Do you suspect foundation problems are causing your garage floor cracks? Give Arch Foundation Repair a call. Schedule a foundation inspection. Get an evaluation with solutions.

Foundation Crack Series

1. How to Repair Cracks Around Window Frames – Quick Guide
2. How to Fix Concrete Floor Cracks in Slab? Ways to Great Results!
3. How to: Filling Cracks Around Door Frames: Expert Ways to Make it Better
4. How to Repair Wall Cracks, When to Worry, & When to Get Help
5. How to Fix Ceiling Cracks DIY Tips – Are Cracks in Ceilings Normal?
6. Signs of Foundation Problems: Why Does Grout Crack / Why Do Tiles Crack?
7. Helpful Ways on How To Seal, Fill & Fix Cracks in Garage Floor
8. Why Brick Walls Crack – When to Worry, Get General or Foundation Repairs
9. How to Amend Clay Soil: Fill the Gap Between Soil and Foundations
10. How to Fill a Gap Between Driveway and Garage & Foundation – Make Helpful Repairs