Trust me on this: if you’re staring down a cracked patio, driveway, or walkway, you don’t have to rush into a full concrete replacement just yet. That’s often the most expensive option—and honestly, a bit of overkill if the damage isn’t severe. Instead, there’s a practical, proven fix called routing and sealing that can save you 30-50% of the cost compared to tearing out and re-pouring concrete. I’ve been in this business for 20 years, and I’ve seen countless homeowners breathe a sigh of relief when they realize a simple repair can restore safety, curb appeal, and function.
What Is Routing and Sealing? Breaking It Down
At its core, routing and sealing is a two-step process designed to repair cracks in concrete slabs. It’s especially common for outdoor surfaces like patios, driveways, and walkways.
Routing the crack: This means cutting or widening the crack so it’s a specific shape and depth, creating a clean groove that’s ready for repair. Think of it like trimming a ragged cut on a piece of fabric so you can patch it properly. Sealing the crack: After routing, the groove is filled with a flexible sealant that bonds well to the concrete and moves with the slab as it expands and contracts. This stops water, dirt, and debris from getting inside, which can cause more damage down the line.Simple, right? But the devil’s in the details, and that’s what I’ll walk you through.
Why Not Just Fill the Crack and Call It a Day?
You might be tempted to grab a tub of concrete patch or caulk from the hardware store and slap it on the cracks. I’ve seen it a thousand times. The problem is, cracks in concrete aren’t just surface-level issues; they move and change with weather and load. If you don’t prepare the crack properly, the patch won’t stick, and the repair won’t last.
Here’s where routing makes a world of difference. Without routing—or what some pros call crack chasing—the sealant or patch has nothing to grip onto. The edges are often too thin or flaky (‘laitance,’ a weak surface layer of cement dust and fines, can build up), and the crack might be too shallow or narrow for the sealant to fill properly.
Routing widens the crack to a uniform size, removes loose material, and creates a clean “key” for the sealant to lock into. It’s like sanding a wooden surface before you paint—it just has to be done.
How Does Routing Work? Tools and Techniques
There are a couple of common ways to route or widen cracks:
- Saw cutting: Using a small concrete saw or angle grinder with a diamond blade, the crack is cut along its length to a specific width and depth, typically about 1/4 to 1/2 inch wide and up to 1/2 inch deep. This creates clean, straight edges. Crack chasing with a grinder: For smaller or irregular cracks, a handheld grinder with a masonry blade can grind the crack open and smooth out edges.
The U.S. Bureau of Reclamation and the National Ready Mixed Concrete Association (NRMCA) both recommend routing cracks before sealing to improve adhesion and durability.
Why Is Saw Cutting Better Than Just Grinding?
Saw cutting produces a more uniform groove, which means the sealant can be applied evenly and performs better. Grinding can create uneven edges and dust that can interfere with adhesion. I always prefer saw cutting for anything wider than a hairline crack.
Cleaning the Crack: The Prep Is 90% of the Job
Once routed, the crack must be cleaned thoroughly. This involves:
- Removing all dust and loose debris with an air compressor or a stiff brush. Sometimes washing with water and letting it dry fully. Ensuring the crack is dry and free of oils, dirt, or anything that will prevent the sealant from sticking.
Skipping this step is like trying to bond two oily surfaces together—it just won’t work.
What Kind of Sealant Works Best? Flexible Sealant for Concrete Cracks
This is the part where many DIYers go wrong. You can't just use any old caulk or silicone. You need a sealant designed specifically for concrete that stays flexible and adheres well.
Here’s what to look for:
- Polyurethane or silicone-based flexible sealants: These move with the concrete as it expands and contracts due to temperature changes. Elastomeric sealants: These stretch and compress without cracking or losing adhesion. Non-sag properties: Sealants that won’t slump or run out of the routed crack when applied vertically or overhead.
Many manufacturers label these as “flexible concrete crack sealants.” Applying them properly means filling the routed groove completely, smoothing the surface, and allowing proper curing time.
How Much Does Routing and Sealing Cost? Is It Worth It?
Concrete replacement can cost $8-$15 per square foot or more, depending on thickness, reinforcement, and site conditions. Routing and sealing cracks, on the other hand, usually runs about $3-$7 per linear foot of crack.
That’s a big difference when you consider the typical driveway or patio has dozens of feet of cracks. hellolovelyliving.com Depending on the extent of damage, routing and sealing can save you 30-50% compared to full replacement.
Plus, the repair can often be done in a day or two, minimizing disruption. It’s a practical way to extend the life of your concrete without emptying your wallet.
Real-World Example: Fixing a Cracked Driveway
Last summer, I worked on a client’s 20-year-old driveway in Ohio. The concrete had multiple cracks ranging from hairline up to 1/4 inch wide, caused by freeze-thaw cycles and a bit of settling.
Here’s what we did:
Used a walk-behind concrete saw to route all cracks to about 3/8 inch wide and 1/2 inch deep. Cleaned each crack thoroughly with a leaf blower and wire brush, then washed and let dry. Applied a high-quality polyurethane flexible sealant designed for concrete. Smoothed the sealant with a putty knife and allowed it to cure overnight.The client avoided a full replacement that would have cost over $5,000. Instead, the routing and sealing cost just under $2,500 and added another 10-15 years of life to the driveway.
When Routing and Sealing Isn’t Enough
Routing and sealing is great for cracks that:
- Are less than 1/2 inch wide Don’t show signs of major structural movement or sinking Are mostly surface-level (not deep or affecting load-bearing capacity)
If you have cracks wider than 1/2 inch, large chunks missing, or your slab is heaving, routing and sealing may only be a temporary fix. In those cases, partial or full replacement might be the safer bet.
DIY or Hire a Pro? What I Recommend
If you have the right tools—a concrete saw or grinder, flexible sealant, and some elbow grease—you can tackle small crack repairs yourself. But remember:
- Measuring and routing: It’s easy to over- or under-cut the crack. Too shallow or narrow, and the sealant won’t last; too deep and you might damage the slab. Cleaning: Dust and debris kill adhesion. Skimping here is the #1 reason DIY repairs fail. Sealant choice and application: Not all sealants are created equal. Ask for concrete-specific products, and follow manufacturer instructions.
For larger projects or if you want peace of mind, hiring a pro ensures the job is done right the first time. I always say, “The prep is 90% of the job,” and pros know how to get that right.
Final Thoughts: Crack Chasing Is Your Friend
Widening concrete cracks for repair—also known as crack chasing—combined with flexible sealant application is a time-tested method to extend the life of your concrete without blowing your budget.
It’s backed by industry pros and organizations like the U.S. Bureau of Reclamation and the National Ready Mixed Concrete Association (NRMCA), so you know it’s not just a gimmick.
Next time you notice cracks in your patio or driveway, think twice before replacing the whole thing. Routing and sealing might be just the smart, cost-effective fix you need.
And if you have questions or want a local pro to take a look, don’t hesitate to reach out. I’ve got a story for every crack, and I’m happy to share what works.