Don’t Fix Your Garage Floor Until You Read This

If you can name it, you can fix it. Those pockmarks, chalky stains and peeling areas are easier to fix when  you know how to identify them.

Concrete cracks are easy to repair so long as they’re not structural. Spalling is the pockmarks that come from freezing and thawing. Aging causes pitting, which looks like spalling but with deeper holes. Salt moving through water to the concrete surface causes laitance and efflorescence. While both are usually harmless, efflorescence can be a sign of structural problems. Consistent puddles of water can point to a serious underlying issue.

You can fix everything from cracks to pitting yourself. Just look for the warning signs that you really should show to a professional.

Garage floor concrete crack

What’s Wrong with Your Garage Floor?

The four types of garage floor damage are:

  • cracking
  • spalling
  • pitting
  • low spots

Garage Floor Cracks

Cracks are thin, long splits breaking the concrete apart.

  • cracking is almost inevitable as floors age
  • extreme thaw and heat cycles encourage cracks

New floors should not crack. Something went wrong in the installation, probably one or more of these:

  • the concrete mix was too wet and weak
  • the floor dried too quickly
  • the control joints were poorly designed
  • the garage was poured onto frozen ground

Garage Floor Spalling and Pitting

Spalling is freeze-thaw water damage. A top layer of concrete peels or crumbles away, exposing aggregate underneath. Pitting consists of small holes that are deeper than the spalling damage. Pitting can be caused by poor installation or age.

Learn the tools and procedures to fix spalling and pitting in our article: How Do You Fix Garage Floor Spalling and Pitting?

Concrete spalling
Concrete spalling


Concrete pitting
Concrete pitting

Garage Floor Low Spots

Low spots are sagging dips in the concrete usually caused by improper finishing during installation. So long as the low spot is not a sinkhole, you can fix it with a grinder or a floor maintainer. Diagnose whether the low spot indicates a bigger problem below. Learn how to fix a garage low spot in our article: How Do You Fix Low Spots in Concrete?

Puddling in a a concrete low spot
Puddling in a a concrete low spot


What’s that White Stuff on the Garage Floor? Laitance and Efflorescence

Some visible symptoms will help you diagnose the garage floor problem. Two of these symptoms are laitance and efflorescence. Both are caused by water moving through the concrete.
Very wide concrete crack

Laitance in concrete
Laitance in concrete

Laitance is a mixture of particles that move up through the concrete while curing. Some laitance is normal for an unsealed garage floor which is why your garage is always a little dusty. If the top layer of your floor is a crumbly and sandy it is because it was mixed with too much water.

Efflorescence in concrete
Efflorescence in concrete

Efflorescence is essentially salt (calcium chloride) stains. Concrete is porous and allows water to transfer through it. Water carries the salt to the surface and leaves behind a stain as it evaporates. Efflorescence can come also from road salts evaporating. If this is a constant problem you could have a moisture barrier issue.


How to Diagnose a Dangerous Garage Floor Problem

Structural uneven concrete crack
Structural uneven concrete crack

Get a professional if your garage has excessive damage or deep structural issues. Learn the danger signs of a bigger problem:

  • cracks where one side is higher than the other
  • cracks or crumbling in low spots
  • a constantly wet garage floor
  • a persistent puddle in one area of the garage

If your garage floor shows any of these symptoms, then there might be a serious underlying problem.

There might be a large accumulation of water attacking the floor from underneath. If your garage floor has a water problem, it will soon have a structural problem, too. Ask a concrete professional to diagnose the problem, and to suggest repair solutions.

Any surface fix applied to a bigger problem will soon wear away. Water can crack concrete into pieces. No amount of do-it-yourself mortar or epoxy will stop that process.

Do You Need to Call in a Professional for Cosmetic Upgrades?

A beautiful, glowing glossy concrete floor is possible. If you want one, you need the right tools, timing, weather, and experience. We’re not fans of putting down paint or epoxy. Unless you can do it perfectly, the garage floor will peel, or have air pockets and bumps.

Here’s our thinking of paint and epoxy. If you read this and still disagree, you probably have the background and talent to do the right preparation. Check these out before continuing:

  1. I Will Never Epoxy My Garage Floor (What I Will Do Instead)
  2. Should I Paint my Garage Floor?

If you hire someone, get a real garage floor refinisher, not a handyman. Without exceedingly good preparation, epoxy and glossy floor finishes just don’t stick well and certainly won’t look magazine worthy. If you want to have a great looking garage floor there are better DIY options.

Why Do Concrete Garage Floors Get Damaged?

Besides the large water and structural issues we just discussed, concrete damage comes from many sources. Cracking, spalling and pitting are caused by temperature changes, de-icing agents, and improper expansion joints. You will also see issues if the concrete mix contained too much water, too little mortar, was forced to dry too fast or too slowly. (source)

Concrete Cracks by Nature

Concrete is very strong, but it is non-ductile, which means that it is not flexible. It resists compression, which makes it great as a building material. Concrete roads and buildings hold up thousands of tons of weight. Ancient Romans built many of their buildings with concrete, which is why they still stand today. However, concrete will not stretch, twist or bend without cracking or breaking.

Concrete Requires Expansion Joints

Concrete expansion joint
Concrete expansion joint

You may have noticed what look like big seams in concrete floors, or wonder why sidewalks and concrete roads have these spaces between the slabs. Why is this concrete not just one big slab? These spaces are expansion and contraction joints.

It is very important not to fill in expansion joints when repairing your concrete floor. Concrete needs to expand.

Temperature changes will make the concrete expand and contract. It expands into these joints, which relieves the expansion pressure. The concrete needs a little space to expand and contract otherwise it will crack. It is very important that you not fill these joints in when working on your garage floor.

Concrete is Porous, and Excessive Water is Dangerous

If you pour a quarter cup of water on your garage floor, it should disappear in about half a minute. If your garage floor is sealed, the water will eventually evaporate. Concrete floors can’t be sealed from the underside. That’s why there should be a moisture barrier between the soil and the floor.

The moisture barrier prevents the concrete from constantly pulling moisture out of the ground. If your garage floor is constantly wet or damp, you may have a water problem from either excessive ground water, a breach in the moisture barrier or a leaking pipe.

What About the Clumps of Salty Dust?

Efflorescence is a white, chalky area on your concrete floor. In and of itself, efflorescence is not dangerous. But it could be a signal that there is a dangerous water problem under your floor. Efflorescence comes from water leaching up through the floor and evaporating.

The evaporation leaves behind calcium chloride (salt), which stains the concrete. Efflorescence might signal a water problem beneath the floor. (source)

What is the Difference Between Concrete and Cement?

Even though the words “concrete” and “cement” are used interchangeably, concrete is really a mixture of cement and aggregate materials like sand and rocks. Some concrete also contains high-tech additives. There are many different mixtures for different purposes. Garage floors are made of concrete, not cement.

Stay Away From These Products and Activities!

You cannot repair concrete with regular concrete. The new concrete will not adhere to the old concrete very well, if at all, and you will need to redo the work in short order.

Do not use self leveling sealers to repair cracks. They are designed to seal the control joints of concrete and are not appropriate for repairing cracks.

Stay away from water-based and latex based products for crack repair as well. Only use epoxy-based repair kits. Water and latex products are not paintable and cannot be sanded. Those products may also shrink over time and pull themselves away from the repair. This shrinking will leave small gaps in your repair. Latex-based products generally dry to a rubbery finish and not a hard concrete-like surface that matches the rest of your floor.

Do not use muriatic acid to try to clean your floor. It is used to etch floors and does nothing to clean away oil or other stains. It will eat away at the concrete but not dissolve the oil. Should you ever use acid, please remember: Wear protective gear! Do not pour acid in an enclosed space! If you need to etch your floor, Rust-Oleum makes a well-regarded concrete cleaning and etching product that is much safer to use than acid.

For more instructions on avoiding muriatic acid but still getting good results, go to our article: How Do You Fix Low Spots in Concrete?

Repair Product Overview

What should you use to repair your garage floor?

When repairing cracks and other damage to your concrete you have two basic options: epoxy-based repair kits and polymerized concrete. Both of these solutions work well but please realize that neither of these will match the color of your current garage floor.

If you are concerned about appearance you will need to paint, cover or resurface the floor after you repair it. Garage floor tile can make your garage look like a NASCAR pit stop. Check out our gallery here: 109 Amazing Garage Floor Tile Designs

There are a vast number of professional grade products out there that require a lot more knowledge and experience than the average person possesses. One professional brand has almost a dozen concrete mixes alone all for different purposes. I’m pretty sure that the distinctions are subtle and apply to larger construction projects. This article is focused mainly on consumer level advice.

Protect Your Garage Floor with Epoxy

Just a quick interruption to ask you: are you sure you want to epoxy that floor? Just be aware of the prep work involved before starting. We explain that here: I Will Never Epoxy My Garage Floor (What I Will Do Instead)

A word of caution: as epoxy cures to a hard material, it gives off heat. If you mixed a pint of epoxy in a container and left it the temperature could get up to 450 deg. It also binds to skin quite well and can give you a nasty burn. Do not perform this kind of repair without wearing protective gear.

Epoxy has two components, a resin and a hardener. These components are mixed, either in a self mixing nozzle or on a piece of cardboard or other disposable surface. The mixture then cures into a hard, sand-able and paintable material.

Unlike concrete epoxy is not porous and resists oils and road salts. It can be mixed with aggregate material (dehydrated sand and other materials) to give it a more concrete-like appearance.

Epoxy cures rather quickly so don’t mix too much at once. Be sure to follow the manufacturer’s instructions about proper mixing ratios and curing times. Also note that the product may become difficult to work with before it is fully cured.

Fix Your Garage Floor with Polymerized Concrete

Even though the words “concrete” and “cement” are used interchangeably, concrete is really a mixture of cement and aggregate materials like sand and rocks.

Polymerized concrete is cement mixed with special aggregate material that allows it to adhere to existing concrete.

We usually don’t think in terms of innovation when it comes to things like this but building materials have become fairly hi-tech and things that we take for granted now simply did not exist a decade or two ago.

There are many different mixtures for different purposes. Just like epoxy, concrete hardens by a curing process. T

he curing process is called “hydration.” This is not simply drying. Hydration is an active reaction that gives off a lot of heat. So much so that when they built the Hoover Dam they needed to install a network of cooling pipes to facilitate the curing process.

Polymerized concrete comes in powder form that you mix with water. It takes longer to cure than epoxy giving you more time to work and giving you a chance to mix enough for a larger area. Follow the instructions and use the proper ratio for best results.

Post Garage Floor-Fix Options

Sila-Tek 3500 Concrete Floor Densifier
Sila-Tek 3500 Concrete Floor Densifier

After you repair your floor you have a few options. If you don’t particularly care what your garage floor looks like, you can leave it just as it is. I would consider using a “densifying sealer” to finish things off. This will help protect your floor from stains, road salts and deicers, and harden the surface to reduce dusting.

One of the best densifiers is Sila-Tek 3500. A densifier like the Sila-Tek 3500 will make your garage floor stronger, protecting the work you just did. One bottle treats 1,000 square feet. Amazon carries it. Check it out here.

You can also resurface your floor with a concrete topcoat for a fresh even appearance or paint it with an epoxy paint (which is difficult enough to do that I would recommend getting a professional to get good results). Another option is to cover the floor with durable plastic tiling that clips together. They look very attractive, protect the floor and can be disassembled should you want to move them. Perfect for renters. Learn more here.

You can also lay out mats specifically designed to protect your garage floor from the ice and snow falling off of your car. Floor containment mats capture the ice and water. When it’s time to remove the moisture, move your car out, and broom the sludge over the front lip and back into the driveway.

People Also Ask

How do you fix a garage floor crack? Use a wire brush, a hammer and cold chisel, or an angle grinder with a crack chasing wheel to loosen and break off nearby concrete. Vacuum away all concrete debris. Fill the crack with epoxy based concrete crack filler. Learn more

How do you fix low spots in garage floor concrete? Use a de-greaser to remove oil from the surface. Use a wire brush, or a grinder, or an acid-substitute, to prepare the concrete. For large areas use a floor buffer with a grinding attachment. Vacuum up loose material. Trowel a patch kit onto the surface. Learn more

How do you fix garage floor spalling and pitting? Test for and remove weakened adjacent areas; clean and prepare the surface to be repaired; and patch the area with an epoxy-based topping. Before fixing the problem, though, check for serious moisture or structural issues that would require professional help to fix. Learn more