What is the best product to seal concrete cracks?

Concrete cracks are a common issue that most homeowners face at some point. Cracks in concrete can be unsightly and lead to further deterioration if left unaddressed. Thankfully, there are many products available today that are designed to seal concrete cracks and prevent further damage. Choosing the right concrete crack sealer depends on factors like the location and width of the cracks, as well as your budget. This article will provide a thorough overview of the best products for sealing concrete cracks to help you make an informed decision.

What causes cracks in concrete?

Concrete naturally shrinks as it cures, which often leads to cracks forming. There are several other potential causes of cracks in concrete:

  • Ground movement – Shifts in the ground underneath concrete can cause it to crack due to expansion and contraction.
  • Freeze/thaw cycles – Water seeping into concrete and freezing can expand cracks over time.
  • Poor installation – Improper concrete installation that doesn’t account for movement or drainage can lead to cracks.
  • Structural issues – Cracks may form if the underlying soil or base materials sink or shift.
  • Heavy loads – Concrete cracks under the weight of heavy vehicles, equipment, or other objects.
  • Tree roots – Growing tree roots can exert pressure on and break concrete.

Identifying the cause of the cracks will help determine the best sealing method and product.

Why seal concrete cracks?

Although concrete cracks are common, it’s important to seal them for the following reasons:

  • Prevent further deterioration – Sealing cracks prevents water and other materials from seeping in and expanding the cracks through freeze/thaw cycles.
  • Improve appearance – Sealed cracks are less visible and make concrete look nicer.
  • Avoid tripping hazards – Filling in cracks makes concrete safer to walk on by eliminating trip hazards.
  • Extend service life – Sealing cracks can add years to the life of concrete by preventing damage.
  • Limit insect/pest infestation – Cracks can provide entry points for insects and weeds to grow. Sealing deters this.
  • Improve functionality – Cracks impact the functional use of concrete for things like driveways and foundations.

In short, sealing cracks as they occur will save you money and trouble down the road. Catching concrete issues early is key.

Types of concrete cracks

Before choosing a sealing product, it’s helpful to understand the different types of concrete cracks:

Hairline cracks

Hairline cracks are small fractures in concrete less than 1/16 inch wide. They generally form due to typical expansion and contraction of concrete. Hairline cracks are common but don’t pose a major structural concern.

Shrinkage cracks

These cracks form as concrete cures due to the evaporation of water and normal shrinking. Shrinkage cracks are usually shallow and rarely wider than 1/4 inch.

Settlement cracks

Settlement cracks occur when the soil or base under the concrete settles unevenly, causing cracks as the concrete drops. They often run vertically or diagonally.

Dormant cracks

Dormant cracks have stabilized over time and show no recent growth or deterioration. Nonetheless, sealing them is a good preventive measure.

Active cracks

Active cracks show signs of recent movement or deterioration, indicating they are still expanding. They are high priority cracks to seal.

How to choose a concrete crack sealer

With many concrete crack repair products available, choosing the right sealer involves considering these key factors:

Location of the crack

The location of the crack impacts how much movement it will experience. Cracks in ground floor slabs or driveways undergo more movement than vertical wall cracks. Flexible sealers are best for cracks prone to movement.

Width of the crack

For hairline, shallow cracks less than 1/8 inch wide, liquid sealers typically work well. Wide cracks over 1/4 inch wide require concrete repair caulk or epoxy sealers that can deeply penetrate the crack.

Application method

Liquid sealers can be applied with a roller, brush or sprayer. Caulks and epoxies require a caulking gun but offer more flexibility and strength. Some products are more DIY-friendly than others.

Paintable options

If you plan to paint over the sealed concrete, choose a sealer labeled as paintable, or it may impair paint adhesion.

Solvent-based vs. water-based

Solvent-based products often adhere better for a more durable seal but have stronger odor and VOCs. Water-based options are lower odor and more environmentally friendly.

Duration of effectiveness

The expected lifespan of sealers ranges from 1-5 years typically. Higher quality epoxies can last 5-10 years. Reapplication needs should factor into product selection.


Concrete sealers range from $20-100 depending on the material and longevity of the product. Higher cost tends to mean longer-lasting solutions.

10 best concrete crack sealers

With a wide range of products available, here are 10 top-rated concrete crack repair sealers:

1. Kryton Krystol T1 Concrete Waterproofing

Kryton’s crystalline technology waterproofs concrete and fills cracks by chemically reacting with concrete to block moisture. It has high bonding strength and is effective for cracks up to 1/4 inch wide.

Key Features:

  • Crystalline technology provides lasting waterproof seal
  • Bonds well to concrete for strong seal
  • Withstands hydrostatic pressure
  • Suits hairline to 1/4 inch cracks

2. Polyurethane Concrete Crack Sealant

Polyurethane makes an excellent concrete crack sealer as it expands into cracks and hardens for a watertight seal. It adheres to most building materials and suited to high movement joints.

Key Features:

  • Flexible polyurethane formula
  • Expands 3x to fill cracks up to 1 inch wide
  • Bonds and hardens for a watertight seal
  • Withstands joint movement

3. Flex Seal Concrete Sealer

Flex Seal is a thick liquid sealer that self-levels into cracks to create a flexible, waterproof rubberized coating. It strongly adheres to concrete, masonry, stucco, gutters and more.

Key Features:

  • Thick liquid coats cracks up to 1/2 inch wide
  • Flexible when dry for high movement areas
  • Strong adhesive bonds to many building materials
  • Easy to apply by rolling or brushing

4. RadonSeal Concrete Patch and Crack Filler

RadonSeal penetrates up to 4 inches into concrete to seal cracks and prevent radon gas entry. It remains flexible after curing and is waterproof against hydrostatic pressure.

Key Features:

  • Seals cracks up to 1/2 inch wide
  • Flexible epoxy formula
  • Waterproof and radon gas resistant
  • Low odor and VOC

5. Quikrete Concrete Crack Sealant

Quikrete Concrete Crack Sealant is a durable, acrylic-based sealer that resists water, freeze/thaw, and behavior. It goes on white and becomes transparent when dry.

Key Features:

  • Seals cracks up to 1/4 inch wide
  • Acrylic-based
  • Applies white, dries transparent
  • Affordable price

6. Loctite Polyseamseal Concrete & Masonry Sealant

Loctite Polyseamseal is a versatile polyurethane sealant suitable for concrete, masonry, stucco, wood, metal and more. It remains flexible to withstand expansion and works in active cracks.

Key Features:

  • Bonds and seals cracks up to 1 inch wide
  • Polyurethane formula stays flexible
  • Can be painted over
  • Adheres to multiple surfaces

7. Siloxane Concrete & Masonry Water Repellent

Siloxane treatments create an invisible, hydrophobic barrier that waterproofs and strengthens exterior concrete. They penetrate deep and durable protection against moisture damage.

Key Features:

  • Repels water on exterior concrete
  • Penetrates deeply into concrete
  • Invisible protection
  • Long-lasting effectiveness

8. Sika Concrete Crack Fix

Sika Concrete Crack Fix is a fast-setting, cement-based patch ideal for structural crack repair. Just mix with water and apply to seal cracks instantly. It gains strength rapidly for a permanent concrete fix.

Key Features:

  • Rapid-setting formula
  • High early strength
  • bonds strongly to concrete
  • Applies easily with trowel or putty knife

9. NP1 Polyurethane Self-Leveling Sealant

NP1 offers superior flexibility and adhesion to fix concrete cracks. Its self-leveling formula pours easily into cracks for waterproof protection. Ideal for high movement joints.

Key Features:

  • Pourable polyurethane sealant
  • Self-leveling formula
  • Strong adhesive properties
  • Seals cracks up to 1/2 inch wide

10. Rust-Oleum EpoxyShield Concrete Patch and Crack Filler

EpoxyShield Concrete Patch permanently seals cracks with an epoxy-based formula. It self-levels for easy application and cures smooth and strong. Provides a great base for garage floors.

Key Features:

  • Flexible epoxy patch and crack filler
  • Self-levels for easy use
  • Cures smooth and hard
  • Ideal for garage floor repair

How to apply a concrete crack sealer

Sealing concrete cracks properly ensures maximum effectiveness and durability. Follow these key steps:

  1. Clean the area thoroughly – Remove all dirt, dust, oil and debris so sealer fully bonds to concrete.
  2. Etch surface for better adhesion – For hairline cracks, etching with muriatic acid creates a rough surface profile for sealers to stick better.
  3. Widen cracks as needed – Active or over 1/4 inch cracks may need chiseling wider so sealers can penetrate deeper.
  4. Apply sealer according to directions – Carefully follow all label instructions for best results.
  5. Tool sealant for a smooth finish – Once applied, use a putty knife or tool to smooth caulk or epoxy flush with the concrete surface.
  6. Allow full curing time before traffic – Most sealers require 24-72 hours before foot traffic or exposure to elements.

Proper surface prep and application are vital for long-lasting concrete crack repair. Consider hiring a professional if you lack the tools or experience with crack sealing products.


In summary, sealing concrete cracks as they occur helps prevent further deterioration and maintain the integrity of concrete surfaces. Polyurethane, epoxy, and liquid acrylic-based sealers provide long-lasting solutions for hairline to 1 inch wide cracks. Location, depth, and width of cracks dictate the best product to use. Kryton, Loctite, Flex Seal, and Quikrete are top brands for DIY and professional use. With the right concrete crack sealer, you can repair and protect garage floors, driveways, basements, slabs, walls, and more. Regular sealing maximizes the life and functionality of the concrete.

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