Repair concrete expansion joints early to save time and money
Thanks to a botched installation (not one of our crew), we had the good fortune of repairing a concrete expansion joint at a local church. If you're not sure how to repair concrete expansion joints, or you're looking for an easier way to get the job done, you're in the right place. We'll show you what went wrong with this installation and give you some tips for fixing it before it becomes a really expensive fix.
NOTE: Many people, including the pros we consulted on this article, use control joints and expansion joints interchangeably. Technically, expansion joints are completely decoupled and allow for intended movement. A control joint is a partial cut that allows natural cracking at predictable locations where cracks can be hidden on the joint line. Because many people use the term swell joint when referring to control joints (think Kleenex vs tissue), we reflect this in this article.
Why You Should Repair Concrete Expansion Joints Before It's Too Late
On our project, the original installer used a combination of foam support rods and concrete expansion joint filler that was too stiff for the application. With only two joint surfaces needing to be glued and not the bottom, the contractor was paid substandard work that left unsightly cracks in the fill when the building was completed less than a year later.
If it doesn't go through a repair cycle, the edges will eventually start to show. This will cause slow corrosion of the sides of the expansion joint. As this "grand canyon" effect erodes the sides over time, it can eventually reach a point where repair costs are prohibitively high.
In a small church, erosion is very slow. But in a warehouse, store, or other high-traffic environment, the equipment will crush the sides and corners more quickly. We've heard of forklifts costing as much as $1 million a year to maintain just because of the severe impact of constantly running over damaged expansion joints.
You can do standard expansion joint repairs up to 1 inch or so. Once you get beyond that, the process can be even more painful for your wallet. You'll need to first cut a gap about 4 inches wide, rebuild a concrete layer, and then cut a new expansion joint. This type of expansion joint repair costs nearly $20 per foot.
Hopefully your facility isn't there yet.
The Difficult Repair of Concrete Expansion Joints
One common method of repairing concrete expansion joints requires some basic tools and a lot of time.
- Use a scraping tool, such as a 5-in-1, to scrape away the old concrete expansion joint filler.
- Vacuum the concrete expansion joints.
- Use a caulk gun with a filler of your choice and refill the joints.
- Scrape the sides and top of the seam, leaving a clean surface.
It takes a lot of time, even in small areas, and most of the time you give in.
Repair Concrete Expansion Joints the Easy Way
Step 1: Sawing and Cleaning the Joint
To remove old concrete expansion joint fillers we start with US Saws Dust Buggy Mark III. This saw features an 8" diamond blade that cuts 2" deep. We only had to cut 1 inch and the 1/4 inch wide blade we used was able to clear the joint in one pass.
With Objective Data, this saw is an OSHA compliant solution that doesn't require any water and runs on a standard 120V, 20A outlet. You need 25 CFM for every 1 inch of blade diameter, so you'll want a vacuum with at least 200 CFM. We used a US Saws model at 220 CFM to keep our surfaces as clean as possible.
Not only is it fast (8 hour shifts can cover up to 10,000 linear feet), but it's also designed to allow you to work while standing and is more accurate than other options available.
It's super fast, cleans, and puts more effort on your back than hand scraping or handheld power tools.
Step 2: Vacuum Connector
This step is unchanged. Simply run the duster over the joints to collect any heavier particles that were missed while sawing.
Step 3: Concrete Expansion Joint Filler
Selecting the correct concrete expansion joint filler is key to obtaining the best results. While our church doesn't have the kind of traffic you'd see in a warehouse, we chose Metzger McGuire Spal-Pro RS 88 – an industrial grade two part polyurea. It is ideal for environments that remain in the 32°F to 120°F range.
This concrete expansion joint filler is thin enough to get into cracks where buildings have settled, but sets fast enough to do it in 10 to 15 minutes. You can use a variety of colors to match or contrast your floors.
Before mixing, we put paint tape on both sides of the seam.
We turned to US Saws' One Man Polymer Pump to apply the filler. It enables a person to properly mix and apply fillers. Like the Dust Buggy, you can keep your knees still instead of crawling around on the floor. It's easy to apply and fills your joints quickly.
We use a dual channel system to apply our Spal-Pro RS 88. The first system allows the concrete expansion joint filler to sink into the joint and fill any cracks beneath it. Fill the seams with a second pass and slightly overfill with floor-protecting tape. Even with two passes, it takes a little more to smooth out the lows.
Step 4: Complete Concrete Expansion Joint Repair
For the final step, we used a homemade spatula. It's intentionally long and heavy to allow us to gain some mass from the standing position. To complete the process, simply grab a spatula and cut under the tape. It cuts the top of the concrete expansion joint filler flush with the top of the floor while removing the tape.
For our Spal-Pro RS 88, we gave it 15 minutes to set up before scraping. Check the documentation on your filling machine to determine how long you should wait.
When you're done with the scraping process, follow the manufacturer's curing guidelines before letting the flow get back on the road.
Equipment List
- US Saws Dust Buddy Mark III Concrete Joint Saw – $1,650
- US Saws One Man Polymer Pump – $7,250
- Metzger McGuire Spal-Pro RS 88 – $450 (10 gallons)
- scraper
- painter's tape
- Chemical Resistant Gloves