Control Joints vs. Expansion Joints: What You Need to Know
When installing concrete flooring, your contractors will likely suggest that you include joints, with control joints and expansion joints being the most common. It’s important for you to understand both kinds so you are prepared to follow your flooring contractor’s suggestions for your facility. Learning the difference between the two will also help you maintain your expansion and control joints in concrete, keeping your facility safe and functional.
Conveniently, you no longer have to wonder, “What is the difference between control joint and expansion joint concrete?” This guide has all of the relevant information you need to know.
Control Joints vs. Expansion Joints
What Are Control Joints: A Summary
A control joint is the most common type of joint you will see in concrete flooring. These are designed to control cracking as the floor cures. Installing and maintaining concrete control joints helps prevent random cracks from forming in the floor over time, even after regular use, shifts in the earth, temperature changes, and more.
What Are Expansion Joints: A Summary
Expansion joints are cut all the way through the depth of your concrete slab. These joints are placed there to allow the concrete to expand and contract without damaging the flooring or its structural integrity.
A Closer Look at Control Joints
Control joints in concrete are sometimes called contraction joints. These joints are cut into the concrete while it is still fairly fresh. Most of the time, it will be cut within about six to 18 hours of a concrete pour. While expansion joints are cut all the way through, control joints only go about a quarter of the way through a slab.
These joints are designed to control the cracking direction as the concrete slab shrinks over time. The goal is for most of the cracking to occur within these control joints instead of the concrete — this extends the durability of the floor while improving its appearance.
Because you want any cracks or movement to occur in the joints, they are placed at the part of the floor with the highest tensile stress. This includes spots in long walls or slabs, as well as abrupt changes in a cross-section.
A Closer Look at Expansion Joints
To better understand expansion joints, remember that concrete will form to the ground’s topography as it dries. But certain parts of the concrete will shrink more, causing stress and pulling on other areas of the slab. The expansion and contraction also occur with changes in temperatures. Heavy loads can also cause extra stress on the floor, leading to cracks.
As mentioned, expansion joints are cut throughout the entire slab. They are then filled with a compressible material or filler.
Including expansion joints in your concrete lets the material expand and contract without creating random cracks. Essentially, an expansion joint will isolate various parts of your slab, letting the entire slab move without causing undue strain on any area.
The way that your flooring expert cuts expansion joints depends on the weather. In hotter weather, they typically use grooving tools while the initial concrete is still wet. But in cooler areas, professionals can cut them using a saw after some hardening has occurred.
To calculate the maximum distance between expansion joints, take the concrete width in inches. Change the units to feet and multiply them by two or three. If your concrete slab is four inches thick, you need joints no more than eight to 12 feet apart.
You will find expansion joints in nearly any type of concrete flooring structure. This includes sidewalks, bridges, pavement, slabs, ships, buildings, piping systems, railroad tracks, and more.
Summarizing the Differences
Based on the above information, you’ll notice that control and expansion joints have different purposes and sizes. They are also installed at different times.
Control joints are specifically designed to prevent cracks from shrinkage as the slab dries, while expansion joints are there to prevent future cracks due to expansion and contraction. An expansion joint is cut through the entire concrete slab. On the other hand, control joints only go about a quarter of the way through it.
Summarizing the Similarities
Both types of joints are designed to prevent your concrete flooring from forming cracks, although they do so in slightly different ways and at slightly different times. Both joint types are also noticeable if you look at the floor closely. As such, most contractors will do their best to either hide the joints (such as under walls) or make them discreet. If an area needs a lot of expansion joints, they may even be turned into an aesthetically pleasing pattern, such as a checkerboard.
Other Types of Joints
Keep in mind that expansion and control joints are far from the only types you will see in concrete flooring. There are also isolation joints and cold joints. Isolation joints separate concrete slabs from other types of surfaces, such as pipes, structural beams, or walls. They are necessary because other surfaces move at different rates than concrete slabs. Cold joints refer to the seam created when you pour one slab and then proceed to pour another next to it.
The Importance of Maintaining Your Joints
Now that you understand the difference between control joint and expansion joint concrete, it’s time to consider maintenance. No matter the type of joint you have in your concrete, it will require regular maintenance. Maintaining concrete control joints is just as important as properly filling them with flexible joint material during the installation process. Make sure your chosen contractor uses the appropriate flexible joint material during repairs as well.
A few potential issues come with joints. If you don’t care for them properly, debris and other items can enter the joints. This could potentially damage them or hurt their functionality.
The other issue with joints is that the edges can start spalling and breaking away. This is especially common in high-traffic areas.
Edges that spall or break away are a serious tripping hazard, putting your team at a safety risk. On top of that, it will cause the concrete to deteriorate. It can even damage your forklifts by increasing wear on them.
Joints Can Become Too Damaged for Simple Repairs
If you notice any of these issues but don’t address them immediately, you can run into even larger problems. If the joint reaches a certain width, you won’t be able to fill it with flexible material, as this would not be strong enough to support a forklift.
In this case, you may need to chip out the entire section and rebuild it with mortar. Only then would you be able to install new, smaller, flexible joint fill. Because this process is more involved, it takes longer and costs more than regular joint repairs.
What Happens During Expansion Joint Repair?
As mentioned, it is crucial to repair and maintain expansion and control joints. The process of repairing expansion joints typically starts with grinding uneven surfaces to make them even. Then, the repair technicians will clear debris. They will then place joint filler to make a level surface. From there, the technicians can cut a new joint into the repaired floor. Finally, they fill it with the flexible joint filler.
Your flooring repair team can also replace or repair the epoxy coating on surrounding parts of the floor.
Find a Reliable Joint Maintenance and Repair Team
Kaloutas is proud to be New England’s premier provider for control joint repairs and maintenance. By specializing in repairs and maintenance, we can focus on perfecting the best techniques and diagnostics for your joints. Our expertise ensures damaged joints are addressed and don’t interfere with your business operations.
Let the experts at Kaloutas inspect, repair, and maintain your facility’s control joints for sturdier, safer floors. Contact us and get a quote today.