Driveway sealing looks straightforward: pour the product, spread it around, let it dry. But the number of sealed driveways that start peeling, cracking, or bubbling within a year tells a different story. These seven mistakes are the most common causes of sealing failure in Ontario — and most of them are entirely avoidable.
Mistake #1: Skipping Cleaning and Degreasing
This is the number one cause of premature sealing failure, and it's depressingly common. Homeowners skip or rush the cleaning stage, apply sealer over a dirty surface, and wonder why the result looks uneven and starts failing within months.
Sealer bonds to the asphalt or concrete surface through a chemical adhesion process. Dirt, dust, and grime act as a physical barrier between the sealer and the surface — preventing proper bonding. The sealer appears to stick initially, but under traffic and temperature change, it begins to separate from the contaminated surface beneath it.
Proper prep means:
- Pressure washing the entire surface at sufficient pressure to dislodge embedded dirt
- Using a broom or leaf blower to clear loose debris from cracks
- Treating vegetation in cracks with an appropriate herbicide or manually removing it
- Allowing the surface to dry completely (24–48 hours) after washing
Pro Tip: Before applying any sealer, run your hand across the dry driveway surface. If your palm comes up black or dirty, the surface isn't clean enough. Do another pass with the pressure washer before proceeding.
Mistake #2: Sealing Over Oil Stains Without Treatment
Oil stains are the second leading cause of sealing failure, and they're insidious because the problem isn't visible immediately. Asphalt sealer (which is petroleum-based) actually bonds reasonably well to fresh oil — temporarily. But petroleum oils contain complex organic compounds that prevent long-term adhesion. Within 3–6 months, you'll see bubbles, blisters, or patches where the sealer has separated from the oil-contaminated zone beneath.
Oil contamination must be treated before sealing with a commercial degreaser specifically formulated for asphalt or concrete surfaces. Apply the degreaser, work it in with a stiff brush, let it dwell, then rinse thoroughly. For heavy, old oil stains, you may need two applications. For very severe contamination that has penetrated deep into the asphalt, you may need to apply a coat of oil spot primer before the sealer.
Never assume the sealer will cover over an oil stain effectively. It won't — not in the long term.
Mistake #3: Applying in the Wrong Weather Conditions
Ontario weather is unreliable, and every year homeowners get excited about a warm day in late September and decide to finally seal the driveway — only to have temperatures drop overnight and ruin the job. Weather-related application failures account for a significant proportion of the early failures we see.
Too Cold
Applying sealer when temperatures are below 10°C (air or surface) prevents proper curing. The emulsion doesn't break down correctly, and the sealer remains tacky or soft. When temperatures then drop below freezing, the uncured sealer freezes, becoming brittle and losing adhesion. It will peel away in large sheets the following spring.
Too Hot
Very hot surface temperatures (above 35°C, which asphalt in full sun can reach on a 28°C day) cause the sealer to dry too quickly. It doesn't have time to penetrate surface pores before skinning over. The result is a surface film rather than a bonded coat.
Too Wet
Rain within 24 hours before application means the surface pores may still contain moisture that prevents sealer penetration. Rain within 24–48 hours after application can wash away or dilute uncured sealer. Always check the 48-hour forecast before and after your planned application date.
Mistake #4: Applying the Sealer Too Thick
This mistake comes from a natural but incorrect instinct: if some is good, more must be better. With driveway sealer, the opposite is true. Thick coats don't cure properly, don't penetrate, and crack.
When sealer is applied too thick, the exterior surface skins over and dries while the interior of the thick layer is still wet. As the interior eventually dries, it shrinks, causing the surface skin to crack. You end up with a driveway that looks like dried mud — fine cracks across the entire surface that trap water and fail within one or two freeze-thaw cycles.
Two thin coats, properly applied and allowed to flash off between applications, will always outperform one thick coat. Each coat should be thin enough that you can see the surface texture through it immediately after application — it will darken as it cures, but it should not be pooling or looking like paint.
"We see thick-coat failures constantly in the spring when homeowners call us about peeling driveways. The sealer cracked and lifted because it was applied too thick and couldn't cure uniformly. Thin coats are not a sign of a cheap job — they're the correct technique."
— David, D&D Home Services Co-Founder
Mistake #5: Not Filling Cracks Before Sealing
Sealer is not crack filler. It cannot bridge a crack — it flows into cracks and provides a thin layer of protection inside them, but it has no structural strength and won't hold a crack closed. Applying sealer over unfilled cracks just puts a thin protective layer inside the crack while leaving the crack itself as a water infiltration point.
Water enters the unsealed crack, gets beneath the sealer coat at the edges, works its way laterally, and begins lifting the sealer from both sides of the crack outward. Within a year, you'll see the sealer peeling in strips alongside every unfilled crack on your driveway.
Every crack wider than approximately 3mm should be filled with an appropriate crack filler before sealing. Hairline cracks can often be sealed over directly, but anything you can fit a fingernail into needs filling first. The crack filler should be allowed to cure fully (typically 24–48 hours for cold-pour products) before sealing over it.
Mistake #6: Using the Wrong Type of Sealer for the Surface
Driveway sealer is not a universal product. The formulations for asphalt and concrete are chemically different, and using the wrong product type on the wrong surface is a mistake that can cause real damage.
Asphalt Sealer on Concrete
Standard asphalt sealer (typically coal tar or asphalt emulsion) applied to a concrete surface won't bond properly because the chemical composition of concrete is fundamentally different from asphalt. The result is a dark, smeared-looking surface that peels and flakes fairly quickly. More importantly, some coal tar sealers can actually stain concrete in ways that are difficult or impossible to remove.
Concrete Sealer on Asphalt
Applying a concrete penetrating sealer (like silane-siloxane) to asphalt provides limited benefit because asphalt has different porosity characteristics. It's not harmful, but it's an expensive mistake that provides minimal protection.
Always read the product label to confirm it's formulated for your specific surface type. If in doubt, ask the staff at a proper landscape or contractor supply store (not a big-box hardware store) for guidance.
Mistake #7: Allowing Vehicle Traffic Before Full Set
Fresh sealer is soft, sticky, and easily damaged for 24–48 hours after application. Driving on it too soon leaves permanent tire marks — particularly from the turning of wheels, which drags the sealer rather than just compressing it. Parking in the same spot for the first 48 hours can also leave indentations if temperatures are warm and the sealer is still soft.
The 24-hour minimum is for light traffic under ideal conditions (warm temperature, full sun, thin application). In cooler temperatures (10–15°C), after an afternoon application, or with heavier sealer, 48 hours is the safer standard. If in doubt, wait longer — the cost of keeping vehicles off the driveway for an extra day is zero. The cost of tire track marks baked into your freshly sealed driveway is the entire job.
During the first 30 days, avoid turning your wheels while stationary, avoid heavy vehicle parking (garbage trucks, delivery vehicles), and be cautious about high heels and bicycle tires, which can leave marks in still-curing sealer on hot days.
Key Takeaways: The 7 Mistakes to Avoid
- ✓ Mistake #1 — No cleaning/degreasing: The biggest cause of failure. Pressure wash thoroughly and degrease oil stains before any sealer touches the surface.
- ✓ Mistake #2 — Sealing over oil: Oil stains must be treated with commercial degreaser; sealer will bubble and lift over untreated oil.
- ✓ Mistake #3 — Wrong weather: Minimum 10°C, dry surface, 48-hour rain-free window before and after.
- ✓ Mistake #4 — Too thick: Two thin coats always beat one thick coat. Thick applications crack as they cure unevenly.
- ✓ Mistake #5 — No crack filling: Fill all cracks over 3mm before sealing; sealer cannot bridge or hold cracks closed.
- ✓ Mistake #6 — Wrong product: Asphalt sealer for asphalt; concrete sealer for concrete. They are not interchangeable.
- ✓ Mistake #7 — Early traffic: Wait 24–48 hours minimum; turning wheels on fresh sealer leaves permanent marks.
Avoid all seven of these mistakes by having the job done right the first time. D&D Home Services provides professional driveway sealing in Kitchener, Waterloo, Cambridge, and Guelph with thorough preparation and commercial-grade products. Get your free quote today.
