Home > A Guide to Sealing Concrete Driveway Joints

A No-Nonsense Guide to Sealing Your Driveway

Why those gaps in your concrete matter, and how to fill 'em right. Your straightforward guide to picking and using driveway joint sealant.
Disclaimer: Visuals are for instructional and illustrative purposes. Always follow proper safety steps and manufacturer directions when performing your own painting tasks.

So, you've got a concrete driveway. And it's got these... gaps. Are they supposed to be there? Yep. Should you fill them? Absolutely. Here's the lowdown on why those joints exist and how to seal them up properly, without getting a headache.

A side-by-side comparison of a clean, professionally sealed concrete driveway joint and an unsealed joint filled with dirt and weeds.

Why Bother Sealing Those Gaps?

Concrete can actually move. It expands in the heat and shrinks in the cold. Those gaps, or joints, are there on purpose to give the concrete room to breathe without cracking itself to pieces.

Meet the Joints

You'll likely see two kinds of joints. Expansion joints are the big, deep gaps, often between your driveway and the garage floor. They handle the major movements of the whole slab.

Control joints are the shallower lines cut into the surface. They're basically pre-planned cracks, encouraging the concrete to crack in a nice, straight line where you want it to, instead of randomly across the middle.

An annotated illustration showing the difference between a deep expansion joint and a shallower control joint on a concrete driveway.

What Happens if You Don't Seal Them?

An empty joint is a welcome mat for trouble. Water gets in and washes away the gravel and dirt packed underneath your driveway. This creates empty pockets, and soon enough, the heavy concrete slabs sink and crack.

A severely cracked and uneven concrete driveway caused by water damage and frost heave from unsealed joints.

In cold climates, it's even worse. Water in the soil freezes, expands with incredible force (a thing called "frost heave"), and pushes your driveway up from below. This causes massive cracks and uneven surfaces.

Unsealed joints also collect dirt, which is a perfect home for weeds. Their roots can slowly wedge the concrete apart. Sealing the joints stops all of this before it starts.

Picking Your Goo: Sealant Types

The goal is to fill the joint with something that’s both waterproof and flexible. This is key. You need a sealant that can stretch and squish as the concrete moves.

Crucial Mistake to Avoid: Never use hard, inflexible fillers like mortar, grout, or wood in your driveway joints. Concrete needs to move, and these materials will crack and fail. Always use a flexible sealant designed for concrete.

Don't just stuff any old thing in there. Using a hard filler like mortar, grout, or even a piece of wood is a classic mistake. They can't flex, so they'll just crack and fall apart, leaving you back at square one.

Works cited

  1. Filling Concrete Expansion Joints: What to Use and What to Avoid, https://www.a1concrete.com/concrete-repair-learning-center/fill-concrete-expansion-joints
  2. Concrete Expansion Joint Repair: Causes And Effects - Houck, https://www.houcks.com/blog/concrete-expansion-joint-repair-causes-effects/
  3. Repairing & Sealing Horizontal & Vertical Expansion Joints ..., https://www.quikrete.com/athome/video-repairing-sealing-horizontal-joints.asp
  4. Advice on how to seal a sloped expansion joint down a concrete driveway - Reddit, https://www.reddit.com/r/Concrete/comments/ng9kdd/advice_on_how_to_seal_a_sloped_expansion_joint/
  5. Joint Sealing: Its Importance in Construction and Maintenance - Superior Waterproofing, https://superiorwaterproofing.com.au/joint-sealing-importance-in-construction-and-maintenance/
  6. How to properly apply and care for concrete sealant- GE Sealants, https://gesealants.com/projects-howtos/how-to-properly-apply-and-care-for-concrete-sealant/
  7. SEALANTS VS. JOINT FILLERS - Euclid Chemical, https://www.euclidchemical.com/fileshare/Literature/Technical_Bulletins/CP-18-Sealants_VS_Joint_Fillers.pdf
  8. What is Sealant? 6 Types of Sealant Used in Construction, https://mtcopeland.com/blog/what-is-sealant/
  9. Concrete Joints & different joints sealant Products - unipaints, https://www.unipaints.com/Joints-sealants-types
  10. How Long Should Quality Sealants and Caulks Last?, https://sealantworx.co.nz/how-long-should-quality-sealants-and-caulks-last/
  11. Silicone sealant vs different types of sealants. - Calfeutrage Apex, https://calfeutrageapex.com/silicone-sealant-vs-different-types-of-sealants/
  12. Polyurethane and Silicone Sealants Key Differences - metrosealant, https://metrosealant.com/polyurethane-and-silicone-sealants-key-differences/
  13. Sealant Replacement Guide for Commercial Building Longevity - Valcourt Building Services, https://www.valcourt.net/blog/strategic-sealant-replacement-knowing-the-right-time-to-replace-building-sealants/
  14. Change the Joint Sealant Before Sealing or Painting Your Driveway ..., https://www.bradthepainter.com/change-the-joint-sealant-before-sealing-or-painting-your-driveway/
  15. Sika-Backer-Rod-How-To-Install-Application-Guide ... - Sika USA, https://usa.sika.com/dms/getdocument.get/b243ccb6-b7b0-4d73-a3f3-85721737bb13/Sika-Backer-Rod-How-To-Install-Application-Guide.pdf
  16. Diagnosing 5 Common Concrete Sealer Problems - Euclid Chemical, https://www.euclidchemical.com/company/blog/archive/diagnosing-5-common-concrete-sealer-problems/
  17. Joint Sealants - Concrete Joint Sealant Products (Polyurethane ..., https://www.wrmeadows.com/joint-sealants/
  18. Sika 3/4 in. x 20 ft. Closed Cell Backer Rod, Expansion Joint Polyethylene Foam 108130, https://www.homedepot.com/p/Sika-3-4-in-x-20-ft-Closed-Cell-Backer-Rod-Expansion-Joint-Polyethylene-Foam-108130/202523820
  19. When to Use Backer Rod: A Comprehensive Guide - metrosealant, https://metrosealant.com/when-to-use-backer-rod-a-comprehensive-guide/
  20. Backer Rod Types and Installation | Tremco Sealants Blog, https://www.tremcosealants.com/blog/backer-rod-types-and-installation
  21. The Right Way To Seal Expansion and Control Joints - YouTube, https://www.youtube.com/watch?v=P28ZpR9I56g
  22. How To Properly Use Backer Rod To Fill Concrete Cracks - YouTube, https://www.youtube.com/watch?v=MhLYA5xZxKs&pp=0gcJCfwAo7VqN5tD
  23. How to Repair & Seal Expansion Joints in Concrete - YouTube, https://www.youtube.com/watch?v=wngw2KvjRJY
  24. After hours of dry time, why are there air bubbles on top of the Sikaflex Crack Flex Sealant?, https://retail.usa.sika.com/en/support/sealants/after-hours-dry-time-why-are-there-air-bubbles-top-sikaflex-crack-flex-sealant
  25. Tech Brief: Joint Sealing - Federal Highway Administration, https://www.fhwa.dot.gov/pavement/pubs/hif18019.pdf
  26. What is the difference between full cure and tack-free cure? - Chemtronics, https://www.chemtronics.com/what-is-the-difference-between-full-cure-and-tack-free-cure
  27. What Does “Tack-Free” Mean? (And Why It Matters for Adhesive Performance) - Seal Bond, https://seal-bond.com/news/tack-free
  28. What is the difference between full cure and tack-free cure? - Techspray, https://www.techspray.com/what-is-the-difference-between-full-cure-and-tack-free-cure
  29. Epoxy Terms and Definitions - Time, https://www.epoxy.com/Epoxy_Terms_Time.aspx
  30. How Long After Sealing the Concrete Driveway Can You Drive On It, https://biondipaving.com/how-long-after-sealing-the-concrete-driveway-can-you-drive-on-it/
  31. When Can You Walk on New Concrete?, https://thisisconcrete.com/walk-new-concrete/
  32. How Long do You Need to Wait Before Parking on New Concrete? - Port Aggregates, https://www.portaggregates.com/wait-before-parking-on-concrete/
  33. How Long Before You Can Drive on New Concrete?, https://www.concretenetwork.com/concrete/concrete_driveways/how-long-before-you-can-drive-on-concrete.html
  34. Signs It's Time to Replace Your Sealant (Any Why it Matters) - Pecora Corporation, https://www.pecora.com/signs-its-time-to-replace-your-sealant-any-why-it-matters/
  35. How to Identify Causes of Sealant Failure in Restoration Construction - Pecora Corporation, https://www.pecora.com/how-to-identify-causes-of-sealant-failure-in-restoration-construction/
  36. The Sealer is Bubbling - ChemMasters, https://chemmasters.net/Sealer_Bubbling.php
  37. What causes the cracking of silicone sealant? How to deal with these problems?, https://www.chinatensan.com/news-show-1002281.html
  38. How to Avoid Concrete Sealer Risks – EpoxyETC, https://epoxyetc.com/blogs/news/is-your-concrete-sealer-killing-you
  39. Safety Data Sheet (SDS) - Concrete Sealers USA, https://www.concretesealersusa.com/content/pdfs/CR305SafetyDataSheet.pdf
  40. Safety Data Sheet - EMI Supply, https://www.emisupply.com/catalog/images/UPLOAD/File/titebond/3192.pdf
  41. SAFETY DATA SHEET JOINT SEALANT PU 3474 - Rotafix, http://rotafix.co.uk/wp-content/uploads/2017/09/Joint-Sealant-PU.pdf