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Epoxy Floor Coatings: Joints

 What is a joint?

When you’re installing concrete slabs shrinking occurs and the slabs crack. Installers often use joints to control where the concrete will crack. In this article, we will be discussing the types of joints that are typically used in residential construction.

Some of our customers have asked us about the white strip they have seen in their garages and basements. These strips are a type of joint that installers use to control the cracking in the concrete. This type of control joint is referred to as a Zip Strip or a point of weakness or POW strip.

How is the Joint Installed?

To install joints in concrete, a plastic strip is inserted into the slab while the concrete is being poured. The joint is usually hidden during the curing stage of the concrete slab. After the slab cures, days later the controlled cracks appear directly above the area where the plastic strips are inserted. Underneath the strip, the cracking continues throughout the slab.

Why are there cuts in my concrete?

To control cracking installers will often use a circular saw and a diamond blade saw to cut lines at 1/3 of the total slab’s depth. These cuts work like zip strips and forces the slab to crack at the bottom of these cuts.

What is an expansion joint?

An expansion joint is a spacer that separates the concrete from the joint material. Joint material is usually made of felt or fibrous board. These joints are most commonly seen in sidewalks. These types of joints allow thermal expansion and contraction of the concrete without damaging the structure of the slabs.

Will the concrete coating systems fill the joints?

No, epoxy and polyaspartic coatings do not fill joints. Look at the following ways we use to control each type of joint:

  1. Zip Strips are filled with thixotropic epoxy paste. The concrete coating can go on immediately after the paste is spread.
  2. Saw Cuts may be left without filler but can be filled with epoxy joint filler (cures overnight) or injectable polyurea(cures in hours).
  1. Tool Joints are filled with an epoxy paste.

Often when garage floors contain saw cuts homeowners prefer to leave the joints open for aesthetics.

If desired the joints can be filled at a later time with caulking designed for concrete flooring.

Can the floor crack somewhere other than the control joints?

It is possible for the concrete floor to crack in other places in the slab but it is not likely.  If cracks were to appear they would follow the joint. The only way this would happen would be if, this was caused by slab vibration, rapid slab expansion/contraction or hydrostatic vapor pressure.

Garage Perfect will work with you if you have any imperfections that you are unsatisfied with after the installation of your flooring. We aim to satisfy our customers. If you have any more questions about concrete slab joints or for a free quote call us today!


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