Concrete cracks are one of the most common issues installers face before applying epoxy or polyaspartic coatings. If cracks are not repaired properly, they will show through the coating and weaken the finished floor.
In this guide, we walk through the basics of repairing concrete cracks using crack filler before installing epoxy flooring. This is also useful when gearing up to install carpet or other types of flooring.
Whether you are a contractor or a homeowner researching concrete floor repair, understanding proper prep work is critical when upgrading your floors.
Why Concrete Crack Repair Matters
Concrete floors naturally crack over time due to:
- Concrete shrinkage
- Temperature changes
- Structural movement
- Settlement
- Moisture pressure
Before applying an epoxy floor coating, these cracks must be repaired. If left untreated, cracks can:
- Show through the coating
- Cause coating failure
- Create weak or sunken points in the floor
- Allow moisture intrusion
Professional installers always repair cracks during the surface preparation stage.
Types of Crack Fillers Used for Concrete
Most professional installers use polyurea or polyurethane crack fillers because they cure quickly and bond well to concrete.
Common crack repair materials include:
Polyurea Crack Filler
- Fast curing
- Flexible
- Ideal for active cracks
- Can be ground flush quickly
Epoxy Crack Filler
- Very strong
- Slower cure time
- Best for structural repairs
Polyurethane Crack Filler
- Slightly flexible
- Good for movement cracks
- Often used in garages and commercial floors
Cementitious Repair Mortar
- Blends more naturally with exposed concrete
- Can be used for cracks, spalls and damaged concrete
- Hardens to a concrete-like finish
- Good option when the floor will remain uncoated
For repairs where the concrete will remain exposed, a cementitious repair mortar can be a better choice than a traditional epoxy or polyurea crack filler.
Unlike resin-based fillers, repair mortar cures to a more natural concrete-like colour and texture. This can make the finished repair less noticeable, especially on commercial floors where the surrounding concrete will not be coated afterward.
Step by Step: How to Repair Cracks in Concrete Floors
1. Inspect the Concrete Floor
Before any repairs begin, the floor should be inspected for:
- Structural cracks
- Surface cracks
- Spalling
- Pitting
- Moisture issues
2. Open the Crack
Installers often widen or clean the crack slightly to help the filler penetrate deeper.
This can be done using:
- A diamond crack chaser blade
- A grinder
- A scraping tool
Opening the crack allows the repair material to bond properly with the concrete.
3. Clean the Area
Dust, debris, and old coating must be removed before applying crack filler. Professional prep usually includes:
- Grinding the concrete surface
- Vacuuming debris
- Removing oils or contaminants
Proper cleaning ensures the crack filler adheres to the concrete.
4. Apply the Crack Filler
The crack filler is then applied directly into the damaged area. Installers typically:
- Fill the crack slightly over flush
- Allow the material to penetrate the void
- Work the filler into the damaged concrete
5. Scrape and Level the Repair
Once the filler begins to set, installers scrape the repair flush with the surrounding concrete.
This prevents high spots and ensures the repair disappears once the floor is ground.
After curing, the repair area can be ground smooth with a concrete grinder before coatings are applied.
What Happens If You Skip Crack Repair?
Skipping proper crack repair can lead to major problems later.
Common failures include:
- Cracks showing through epoxy
- Coating delamination
- Weak areas in the floor
- Moisture penetration
Strong Floors Start With Proper Repairs
Concrete cracks are normal, but they must be repaired correctly before installing epoxy or polyaspartic floor coatings.
Using professional crack fillers and proper surface preparation ensures the finished floor remains durable, smooth, and long-lasting.
For installers, this step is not optional. It is the foundation of a high-quality coating system.
FAQ’s About Concrete Crack Repair
Many installers use polyurea or polyurethane crack fillers because they cure quickly and bond well to concrete. These products can be scraped and ground flush within minutes, making them ideal for concrete floor preparation before coatings or flooring installation.
Yes. Cracks should always be repaired before installing epoxy, polyaspartic, or other concrete coatings. If cracks are not filled properly, they can telegraph through the coating and weaken the finished floor.
Yes. Repairing cracks in concrete is important before installing carpet, tile, vinyl, or laminate flooring. Uneven or damaged concrete can cause flooring materials to wear unevenly or fail prematurely.
Fast-cure crack fillers like polyurea can begin curing within minutes. This allows installers to scrape the repair flush and continue grinding or surface preparation shortly after the repair is completed.
If cracks are properly filled, scraped flush, and ground smooth during surface preparation, they should not be visible through epoxy or other concrete coatings.
