Concrete Crack Repair and Joint Infilling
There are 4 kinds of cracks or joints you may have to prepare before you install an epoxy floor. If you ignore these and just install over them then your finished floor will likely form cracks as well.
Irregular Crack
This is an irregular crack in the slab that does not follow a designated cut joint. We recommend treating them by:
- Fill them with EJSL1636 Epoxy Crack Filler
- Prime a path 16” wide with EEPR0278 Flexible Broadcast Primer with the crack in the middle
- Embed a thin fibertape mesh over the crack into your wet primer. Available here or here.
- If the crack is more than 1/8” wide in some places than there is a good chance that the concrete may still be moving some. We recommend installing a saw-cut control joint over it (once the floor is finished) to give it a place to move without compromising the seamless floor.
Non-Moving Control Joint
We can either
- Trust that they will not move and treat them as an irregular crack (see above) or
- The safest method is to realize that concrete always moves and “honor” them as a Contraction or Control Joint (see below)
Contraction or Montrol Joint
We “honor” these by:
- Marking the ends on the wall so the centers of the joints can be located once the floor is finished.
- Make a sawcut through the finished floor at a minimum depth of 1” with a crack chaser or concrete joint clean-out saw. Refer to the joint sealant manufacturer’s product data sheet for the recommended depth.
- Often you’ll need to insert a foam backer rod into the joint – but again, joint sealant manufacturer’s product data sheet.
- Fill in the joint with a flexible joint sealant. The balance of flexibility vs hardness depends on the use of the floor. We recommend consulting Metzger/McGuire to choose the proper filler. Typically, we would recommend Metzger/McGuire Spal-Pro RS 65 for Retail or Commercial areas and Metzger/McGuire Spal-Pro RS 88 for Industrial areas.
Tip
Put down a wide tape over the joint prior to cutting then remove it as you’re cleaning off the joint filler. Saves time from having to meticulously tape wither side of the joint after cutting. Test this first in a small area, as it doesn’t always work, sometimes the crack chaser saw tears up the tape or leaves a jagged edge.
Expansion Joints
Expansion Joints are usually through the entire slab rather then just a cut joint. They allow for more movement than a cut joint. These are not saw cut and filled by the flooring contractor, instead an expansion joint is installed. There are many different types of expansion joints, some can be installed bt the flooring contractor and others are structural.
