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What’s Cracking? Dealing with Cracks in Epoxy Coatings

Epoxy floor coatings are most commonly used in garages and basements. This blog is focused on those two areas of epoxy coating although, some of the information in this blog can also be applicable to commercial epoxy flooring.

What the crack?! How did that get there?

Overtime most concrete flooring develop cracks. This is due to the character of concrete. Cracks can range from small and unnoticeable to hidden within the control joints. There are two main types of cracks, shrinkage and settlement.

  • Shrinkage cracks: These cracks are the most common. They develop as the concrete cures. During the curing process the volume of the concrete decreases because of the evaporation of water content. This forces the weaker parts of the concrete to develop cracks.

There is more than one category of shrinkage cracks which include:

o   Drying shrinkage- Appears as a jagged crack that occurs in a 3-point pattern

o   Map-cracking (or plastic shrinkage)- Resembles a spider-web pattern on the surface of the concrete

o   Plastic settlement cracking- Causes discreet, parallel cracks on the surface of freshly poured concrete. These cracks usually occur around the location of the reinforcement of the slab (from rebar, wire mesh, I-beams or footers). 

  •  Settlement cracks: These cracks are the result of a structural failure typically caused by elevation changes. This results in one side of the crack to be lower than the other.

Shrinkage cracks are the lesser of the two evils. Shrinkage cracks are to be expected to some degree depending on the makeup and placement of the slabs. Settlement cracks are more serious and need to be examined to determine if the cracking will continue.

Does Epoxy Coatings Fill Cracks?

The short answer to this question is no, epoxy coatings can’t fill cracks. If the cracks are created from curing or the settling of the floor, our experts normally cut the cracks to remove the loose materials (crack chase). The act of crack-chasing creates a clean bondable surface inside the cracks. Once the cracks are cut they are then vacuumed out and then filled with the suitable materials.

If you are dealing with settlement cracks due to the movement of sections of the concrete, this is a bigger issue. When dealing with this issue we would have a Garage Perfect expert work with our customer to determine the best possible remedy for the problem.

The materials used to repair cracks vary depending on the width and depth of the cracks, floor temperature, surface condition and porosity of the concrete. Garage Perfect frequently uses these types of crack fillers:

  • A two-part epoxy
  • Fast setting polyureas
  • Slow setting thixotropic (thickened) epoxies
  • Hybrid polymers that fill wider or deeper cracks

Will my choice of coating affect the visibility of cracks?

The answer to this question is yes. The visibility of the original crack or formation of new cracks depends upon slab vibration, slab expansion and contraction and hydrostatic vapor pressure. Depending on the size of the crack it may be better left alone.

What can you do if I use silicone caulking on my flooring?

Typically, if you use silicone caulking to fill cracks in your flooring our Garage Perfect expert installers can remove it from cracks during the surface preparation process. We then refill the cracks with the appropriate polymer repair materials.

Why do the cracks in my garage/basement flooring have white strip in them?

These cracks are common, they are a type of control joint. The white strip is made of plastic and is referred to as a Zip Strip (point of weakness or POW strip). This strip is put there intentionally to control the cracking. The plastic strip is installed while the concrete is poured and is usually hidden during the curing process. After a few days, the cracks appear above the zip strip. Below the strip the cracking continues below the slab.

Why does My Concrete Slab Have a Joint?

Freshly poured concrete tends to crack during the curing process as the slab shrinks. Control joints are placed into the slab to strengthen the weak spots and control where the cracks will appear.

Why does My Concrete Slab Have Straight Cuts?

When a concrete slab has straight cuts, it contains a control joint called a saw cut. After the concrete flooring is poured a circular saw with a special blade is used to cut lines at approximately 1/3 of the slab’s depth. The slab cracks at the bottom of the cuts during the curing process.

What Can I Do to Help with Expansion and Contraction of My Slab?

Adding an expansion joint to your concrete floor fully separates the concrete pours with a felt or fibrous board. These joints are commonly used in sidewalks. Typically, expansion joints are used the outer perimeter.

Does my garage floor have a different joint than sidewalks?

Sidewalks typically have several tool joints (decorative control joint) placed in a row, alongside an expansion joint. Tool joints can be used in garage and basement floors but it’s not a common practice.

How do you fill the joints?

Garage Perfect uses a different filling approach to each of the joints. Typically, we use the following methods accordingly:

  • Zip Strips –  are filled with a thixotropic epoxy paste.
  • Saw Cuts – Can be left open or can be filled with an epoxy joint filler. For projects with a shorter timeline the cuts may be filled with an injectable polyurea. Depending on the desired look when the saw cuts are left open it may be deemed as decorative (as in the picture).
  • Tool Joints – Are filled with an epoxy paste. The joints later appear as decorative lines in the floor finish.

After the initial cracking, it is unlikely that a garage or basement floor will crack again. Cracking usually occurs in the joints of the concrete slab. This is a rare occurrence and if it was to happen our dedicated staff here at Garage Perfect will devise a solution for the joint repair that is suitable for your needs. Give us a call today (613) 288-9315 or book a free consultation with one of our local experts.

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