One of the most common questions we hear from homeowners is:
“Can you fill the control joints in my concrete?”
The answer is: Sometimes—but not always. Whether a control joint should be filled depends on why it was installed and how your concrete slab behaves.
What Is a Control Joint?
Control joints are intentional cuts placed in concrete to encourage cracking in a controlled location. As concrete cures and naturally expands and contracts with changes in temperature and moisture, these joints help relieve stress and reduce random cracking.
In other words, they’re designed to move.
When Can Control Joints Be Filled?
Control joints can often be filled when:
- The concrete slab has fully cured and stabilized.
- The joint has shown little to no movement over time.
- The goal is to create a cleaner, more finished appearance.
- The condition of the slab indicates the joint is no longer serving as an active movement joint.
Many property owners choose to fill stable control joints because they prefer the seamless look and find the surface easier to sweep and clean.
When Should Control Joints NOT Be Filled?
There are situations where filling a control joint isn’t recommended.
Avoid filling a joint if:
- The joint is still experiencing noticeable movement.
- The slab is prone to seasonal expansion and contraction.
- The joint is functioning as an active expansion joint.
- There are signs the joint is protecting the slab from cracking elsewhere.
If an active joint is filled, the movement may cause the filler to crack, separate, or transfer stress to another area of the concrete.
Every Concrete Surface Is Different
There isn’t a one-size-fits-all answer. Two concrete slabs installed side by side can behave differently depending on soil conditions, moisture levels, age of the concrete, and how the slab was constructed.
That’s why, at All Sealed Up, we evaluate every surface individually before making a recommendation. Our goal isn’t simply to make the concrete look better today—it’s to ensure it performs well for years to come.
Our Recommendation
If you’re considering a polyaspartic coating, ask about your control joints during your estimate. We’ll inspect your concrete, explain your options, and recommend the approach that’s best for your specific surface.
Sometimes that means filling the joints for a cleaner appearance. Other times, leaving them as designed is the smartest long-term decision.
A beautiful, long-lasting coating starts with making the right preparation choices—and knowing when not to change what the concrete was engineered to do.
