Why You Need To Seal Your Concrete Garage Floor Today

Damp Proof Your Garage Floor

These days, a garage is not just for storing cars. It has become a multifunctional space – workshop, extra storage space, a place to exercise or play ping pong, entertain family or friends, and an opportunity to improve the market appeal of your house. A dank, dirty garage floor with unsightly water and oil stains, grease marks, efflorescence, cracks, and spalls, is not only an eyesore, it also lowers the resale value of your house. According to real estate trends, a well kept garage is a valuable upgrade and considered a luxury for potential buyers:

“They’re for more than parking cars, stacking boxes, and holding trash bins. The garage can help sell your home if you stage it right. Most homeowners might think of staging their kitchens and bedrooms, but the garage is a feature that is playing an increasingly important role.” - RealtyTimes®

Whether you’re interested in protecting the garage floor against staining, pitting, crumbling, cracking, dusting, wicking water, or searching for a solution to high humidity levels and mold growth, the most important thing you can do is to seal it with the best penetrating concrete sealer. Protecting your garage floor against deterioration will increase the resale value of you house by $1,000's.

Whether you’re planning on finishing your garage floor with paint or epoxy coating, interested in protecting the floor against staining, cracking, wicking water, dusting, pitting, and crumbling, or searching for a solution to regulate humidity levels and mold growth, the right sealer will be the most important thing you can do for your garage floor and space.

What Can Damage a Concrete Garage Floor?

The floor in your garage or car port takes a beating, and although concrete is an enduring material, it won’t last forever. Let’s look at some of the common causes of damage to a typical garage floor:

  • ENGINE FLUIDS: Oil, transmission fluid, and antifreeze from leaking engines or vehicle maintenance. Engine fluids penetrate into the concrete, produce ugly stains and cause degradation.
  • DEICING CHEMICALS & ROAD SALTS: Typically dragged from the road into the garage on your vehicle. These chemical are particularly harmful to concrete by attacking it chemically. They form a liquid brine on your garage floor which penetrates deeply into the pores of the concrete. Once the brine gets diluted enough with water, it produces damaging freeze/thaw cycles inside the concrete in car ports.
  • GROUND MOVEMENT: Concrete can crack and heave as the soil around it settles and shifts over time. The soil underneath the garage slab may settle and create a void. Clays retain a lot of moisture and some expand when wet and shrink when dry. In colder climates, the water under the floor can freeze and expand upward causing damage.
  • MISSING VAPOR BARRIER: Most garage slabs are poured directly on gravel without first installing a plastic vapor barrier. This causes wicking of water and infiltration of water vapor. Moisture gradually disintegrates the concrete by crumbling, spalling, and pitting.
  • WICKING WATER: Concrete is very porous and when in contact with water, it naturally pulls the water in by wicking action. This shows up as dark, damp spots on the floor or as efflorescence (white minerals leached out from the concrete).
  • WATER VAPOR PERMEATION: Water from the soil evaporates and oozes indoors through the pores in concrete. Putting down a rubber mat or cardboard box will trap the moisture and leave a damp spot. Even strong coatings like epoxy or urethane will eventually bubble up and crack due to the vapor pressure.
  • SWEATING CONCRETE: Concrete porosity allows cold air from the ground below to permeate through it and cool the surface. When the air is warm and humid, condensation forms on cold concrete floors. Moisture gradually damages concrete and activates efflorescence.

Peeling paint on garage floorYour First Step before Painting or Coating Garage Floors

Floor paints and coatings trap water vapor coming up from below. Even the strongest concrete coatings will bubble, peel, or crack (pictured) due to the moisture wicking through concrete, water vapor pressure, pushing efflorescence, or alkali attack.

If you plan to paint your garage floor or apply a coating, like epoxy or urethane, sealing and waterproofing your concrete becomes a critical first step! And you will definitely not choose a film-forming concrete sealer. You need a penetrating concrete sealer that seals the concrete deep inside against water vapor transmission.

Choose the Appropriate Concrete Sealer for Your Garage Slab

These selected penetrating sealers are the top performers. They waterproof concrete permanently (no re-application needed). They do not change the appearance of concrete and do not make the surface slippery. Each sealer leaves the surface paintable and protects coatings from vapor pressure and efflorescence. They are water-borne, user- and environment-friendly, allowing them to be used safely indoors without noxious fumes.

RadonSeal Deep-Penetrating Concrete Sealer - #1 Choice for Sealing Against Wicking WaterRadonSeal Garage Floor Sealant

RadonSeal® penetrates up to 4" into concrete, chemically reacts, and seals the concrete permanently against water seepage, water vapor infiltration, and even radon gas. Stops hydrostatic pressure (from positive or negative side. Stops wicking of water and efflorescence. Protects garage slabs against road salts, brine, and deicers. Strengthens and preserves concrete against cracking, spalling and pitting. Hardens the surface against dusting. Accepts all types of paints, coatings, levelers, water-based stains, and concrete dyes.

KEY BENEFITS: Permanent, waterproofs, protects against road salts, deterioration. Protects paints, clear coatings, levelers, against alkali attack and efflorescence.

BEST USED AGAINST: Negative side water, wicking water, high humidity, shoddy (weak) concrete pours, purged efflorescence, surface spalling, cracking, and freeze-thaw.

APPLY TO: Bare garage floors and car port slabs over 3 inches thick, new or old concrete. Use before applying garage floor paint.


LastiSeal Brick & Concrete Sealer - Best Used For Positive WaterproofingLastiSeal Garage Floor Sealant

LastiSeal® is also a deep-penetrating sealer (2-4" deep), which fills the pores inside concrete and hardens similarly to a hard plastic. Waterproofs. Repels water and most spills can be simply wiped off. Strengthens the concrete. Reduces vapor transmission. Except for latex and silicones, LastiSeal is a great primer for epoxies, urethanes, acrylics, and other paints.

KEY BENEFITS: 15-Year Service Life, repels surface water, strengthens concrete,, deep penetration, clear.

BEST USED AGAINST: Positive side water, chemical and oil spills, cracking, spalling, and pitting of the surface, water vapor transmission, freeze-thaw.

APPLY TO: New or old concrete floors, pavers, cementitious underlayments (test porosity first), fiber-reinforced concrete (test porosity first), acid-stained concrete, integrally colored concrete, stamped concrete (test porosity first).


Ion-Bond Armor Penetrating Elastomeric Sealer - OptionalIonBond Armor Garage Floor Sealer

Used mainly as a supplemental sealer after the application of RadonSeal. Ion-Bond makes the seal against water vapor, as well as radon gas, even tighter. Ion-Bond has the ability to repel spills at the surface which can then be easily wiped off. It does not change the appearance of the concrete, does not make is slippery, and leaves the surface paintable.

KEY BENEFITS: Cures inside concrete but closer to the surface, protects against positive- and negative-side water pressure, paintable, makes concrete easier to clean. Permanent.

BEST USED AGAINST: Wicking water, surface spills, road salts, freeze-thaw.

APPLY TO: Concrete deep-sealed with RadonSeal, smoothly troweled concrete (etching may still be required), thin concrete slab (<3" thick), fiber-reinforced concrete (test porosity first), extremely porous concrete.


How to Clean and Prep Your Concrete Floor

Regardless of the which of type of sealer or paint you’re considering, the first and most important part of the process is to prepare your concrete slab. It is common for a garage floor to have a smooth, machine-troweled finish.


Stains, old paints, oil, grease, or anything else on the concrete must be removed before applying a sealer. Although this is often the most labor intensive step in the process, with the correct cleaning agent(s), this task can be made quicker and safer. Cleaning agents are easy to find but not all are created equal. RadonSeal offers a line of commercial-grade concrete cleaners that can make short work of those nasty stains, and old paints.

Lightning Strip – Paint & Mastic Remover

Novion Universal Concrete Cleaner & Degreaser

RadonSeal Efflorescence Cleaner


Etch and Clean Your Garage Floor with PowerEtchRoughening up the surface by shot-blasting or grinding can clean and open the up the pores, particularly in hard-troweled concrete floors, before painting, sealing, or staining. However, chemically etching the concrete remains the most popular method. It uses a chemical (usually acid) to “eat” away the top layer of concrete. This will remove efflorescence, improve the “grip” for paints and coatings, and open the pores of your concrete for penetrating sealers or stains. It will also reduce pH (alkalinity) of new concrete.

Although muriatic (hydrochloric) acid is the traditional method (as well as the cheapest), it is difficult to work with and the acid and its fumes are dangerous to people. Consider the safer alternatives:

PowerEtch Concrete Etcher & Cleaner (#1 Choice) - Industrial-strength concrete etcher that is non-corrosive to the skin and will not burn concrete. Low odor makes it ideal for indoor use.

EasyEtch pH Reducer & Etcher - Uses citric acid which requires more elbow grease for scrubbing but avoids the risk of chemical burns, hazardous fumes, and toxic runoff.


Cracks are one of the most common problems with concrete floors. Not only do they look bad, they tend to “grow” over time, and often lead to other problems like spalling, crumbling, and water seepage. Crack repair may seem like a daunting task, however, with the right product, repair can be a snap!

RadonSeal provides CrackWeld DIY and Professional Floor Repair Kits designed specifically for cracks in poured concrete floors. This is a permanent repair. Unlike caulks or other methods, it is a full-depth repair. It will fill the full depth of the crack and hold it together, so that it cannot move or expand, and propagate through a surface coating. Use CrackWeld mixed with sand to fill holes or spalled surfaces with a repair that is stronger than concrete.

TIP - Repair cracks before sealing the concrete to avoid affecting the adhesion of CrackWeld to the surfaces of cracks.


Q: "I am concerned that if I use your sealer it will interfere with the adhesion of the epoxy garage paint I plan on using afterwards? Is my concern legitimate?" - Jeff W., AZ

A: Your concern is legitimate but when our penetrating sealers are applied properly, they do not change the surface profile of the concrete thus, allowing for the use of paints and coatings without failure. To assure the sealers are absorbing readily through a smooth surface cap and for good adhesion of the epoxy, etch the concrete surface with PowerEtch® before applying the sealer.

Q: "How do I remove the paint that is chipping from my garage floor?" - Jason C., OH

A: Removing paint can prove to be a tedious endeavor. Basically there are two methods at removing paint – chemical and mechanical. An effective paint stripper, floor scraper, and pressure-washer may be the only tools you will need.

If the use of chemicals and "elbow-grease" proves to be too difficult or costly, rent a concrete floor grinder or shotblaster (using softer beads) to remove the paint.

Mold growth on garage floor carpetQ: "I have carpeting on part of my garage floor and there is mold growing under the paint cans that I store in there (pictured). The carpet is damp so I know it's due to moisture underneath. I plan on ripping out the carpet and sealing the floor with RadonSeal. After applying how long do I have to wait until I can put carpeting back down? What if I decide to paint instead?" - Deb H., DE

A: RadonSeal® has the ability to purge loose minerals and dirt from inside concrete to its surface for days after the application. Erring on the side of caution, we recommend you wait 10 day before applying paint, surface levelers, or adhesive. But loosely laid down carpeting can be placed once the concrete has dried (after two days).

Q: "The stem wall in my garage has efflorescence and is popping the paint. Which product would work best at preventing this from happening again?" - Terry A., MI

A: Once the paint has been successfully removed, seal the concrete with RadonSeal® Plus. RadonSeal stops water migration through concrete, which in turn will prevent the formation of efflorescence.

Q: "I have a high humidity issue inside my garage which I use as a woodworking shop and storage for my tools. How can this be rectified?" - Mike, DE

A: Apply RadonSeal® to the slab to reduce humidity in the garage space by restricting water vapor inflow and cold ground air infiltration through the concrete.

Q: "I'm looking for a concrete sealant that will make it easier for me to clean after the winter months. Is the LastiSeal the best choice for this?" - Danny B., MI

A: Yes. LastiSeal has the ability to penetrate deep into concrete and when enough of the product has been applied, it will also fill the pores much closer to the surface. Making it a superior stain-resistant sealer for years to come!