The purpose of this blog is to deal with questions we get so often when it comes to epoxy floor coatings. Since these questions most often come from residential homeowners concerning their garage or basement floors, I’ll concentrate our answers to this audience. A fair amount of the information is applicable to the commercial environment as well.
Here in part 1 of this blog, I’m tackling some of the common questions concerning cracking of the concrete surface. Next week in part 2, I’ll get into the types of joints used in residential construction and how they impact the installation and performance of the coating system.
Why did my concrete floor develop cracks?
Most garage or basement floors develop some form of cracks, due to the nature of concrete. They may be so small as to go unnoticed or the cracks may be “hidden” within the control joints (more about this in Part 2 of this article). The cracks most homeowners see in their garages or basements fall into one of the following types:
- Shrinkage cracks: These cracks are the most common and develop as the concrete slab cures. The curing process decreases the volume of the concrete mass due to the evaporation of water content and force the concrete to develop cracks in the weaker parts of its construct.
Shrinkage cracks may fall into one of the following categories:
o Drying shrinkage typically causes a jagged crack that occurs in a 3-point pattern.
o Map-cracking (or plastic shrinkage) creates a spider-web looking random pattern on the surface and the cracks often have very little depth.
o Plastic settlement cracking causes discreet, parallel cracks that appear to tear the surface and usually appear while the concrete is fresh. The cracks often reflect the location of the reinforcement of the slab (from rebar, wire mesh, I-beams or footers).
- Settlement cracks: These cracks result as a structural failure where elevation changes have caused one side of the crack to be lower than the other. These cracks are often called “moving cracks” as the cracks completely traverse through the slab and allow each piece to move independent of the other.
Shrinkage cracks are typical and to be expected to some degree, dependent upon the slabs make-up and placement. True settlement cracks may be more serious and need to be evaluated in greater detail to determine if the cracking will continue.
Does the epoxy coatings fill in the cracks?
We don’t rely upon the actual layers of the epoxy or polyaspartic coatings to fill in the cracks in a garage or basement floor. If the cracks are there from the initial curing or settling of the floor, our teams normally crack-chase (or cut) the cracks to remove the loose materials. Crack-chasing also creates clean, bondable surfaces inside the cracks. The cracks are then vacuumed out and then filled with the appropriate materials. If the cracks are “moving” due to movement of sections of the concrete, our specialists will work with the customer to determine what may be safely done to the repair the cracks, which may involve other parties to correct the movement issues with the slab.
The crack repair materials used can vary, depending upon the width and depth of the cracks, as well as floor temperature, surface condition and porosity of the concrete slab. The materials could be quick-set 2-part epoxy crack fillers designed to be coated over immediately or fast setting polyureas. Or, they may be slow setting, thixotropic (thickened) epoxies or hybrid polymers that fill wider or deeper cracks and setup over a period of hours or days.
What if the cracks are filled with silicone caulk?
Our installation teams will remove any caulk from cracks during the surface preparation process and refill with the appropriate polymer repair materials.
Will the cracks return through the coatings?
Unfortunately, the answer is “maybe”. Since the return of the original crack or formation of new cracks that show through the coating depends upon many factors (such as slab vibration, slab expansion & contraction, hydrostatic vapor pressure), there really are no guarantees regarding cracking. Anyone who guarantees a concrete slab will never crack or that the crack will never telegraph through the coating is making a foolish statement.
I can tell you after 10 years in the business that reappearance of cracks through garage floor coatings is not common for Pennsylvania, Maryland and Virginia. Plus, using a coating such as a decorative chip decreases the likelihood that a very small, tight crack would even be easily visible in the coatings. My own garage floor has a crack in the coating that appeared about 4 years after it was installed, but I only noticed it due to getting down on my knees to remove some road tar and then I could see it. I never bothered to fix it, as the fix would be more noticeable than the crack and its presence poses no issues for the coatings performance.
Why do the cracks in my garage floor have white plastic strip in them?
Those cracks are actually a type of control joint (which I discuss in the next part of this article) and the white plastic is what’s referred to as a Zip Strip (also known as a point of weakness or POW strip). These are very common in garage and basement slab construction.
Read part 2 of this blog here.
If I didn’t answer your question, feel free to contact us by replying to this blog or give us a call at 888.577.0452 (PA), 443.299.2963 (MD/DC) or 571.353.0108 (VA).
Mike Mincemoyer has 12 years of experience with the design and execution of repairs to concrete slabs. His installation teams have helped thousands of homeowners with the surface preparation, crack repairs and coatings installations required to give them a beautiful garage and basement floor.