Concrete driveways are an excellent long-term investment — if they're properly protected. In Ontario, the combination of road salt, freeze-thaw cycles, and UV radiation creates a uniquely harsh environment that can reduce the lifespan of an unsealed concrete driveway from 30+ years to 15 years or less. Sealing is the most cost-effective intervention available, and understanding how and why it works will help you do it right.
Why Concrete Needs Sealing in Ontario
Unlike asphalt, which is inherently somewhat flexible, concrete is rigid. That rigidity is both its strength and its vulnerability. Concrete is strong under compression but brittle under tension — and Ontario winters create a great deal of tension through freeze-thaw cycling.
The fundamental issue is that concrete is porous at the microscopic level. It contains countless tiny voids and channels that allow water to penetrate the surface. In a mild climate, this isn't a major problem — water moves in and out without causing damage. In Ontario, where temperatures regularly cycle through freezing and thawing dozens of times per winter, that water becomes a weapon.
When water inside concrete freezes, it expands by approximately 9% in volume. This expansion creates tremendous internal pressure. The concrete cracks minutely. The crack fills with more water. It freezes again. The crack grows. Over years, this process produces the characteristic surface scaling and spalling — the pitting, flaking, and crumbling of the concrete surface — that's common on older Ontario driveways that haven't been sealed.
Road Salt's Role in Concrete Damage
Freeze-thaw cycling alone is damaging enough. Pair it with road salt, and the damage accelerates significantly. Road salt (sodium chloride) works by lowering the freezing point of water — it melts ice. But in doing so, it also creates more liquid water at temperatures where concrete would otherwise be dry and frozen. More liquid water means more freeze-thaw cycles and more ice lens formation within the concrete.
Additionally, chloride ions from road salt penetrate concrete and react with calcium silicate hydrate (the primary binding compound in concrete) to produce more soluble compounds that leach out over time, weakening the concrete matrix. In concrete driveways near roads or in areas where vehicles bring in road salt, this chemical attack can be severe.
The visual result is surface scaling — thin layers of the concrete surface flaking off — and eventually deeper pitting. Once spalling begins, it accelerates. Damaged surfaces collect more water, experience more freeze-thaw cycles, and continue to deteriorate even faster.
Pro Tip: Never use rock salt (sodium chloride) or calcium chloride on a concrete driveway, especially during the first two winters after installation. Even sealed concrete is vulnerable to deicers. Sand provides traction without chemical damage and is the safest option for concrete surfaces.
Penetrating vs. Film-Forming Sealers: Which Is Right for Concrete?
This is the most important decision in concrete sealing, and it's different from the asphalt sealing world. The two fundamental categories behave very differently and have different applications.
Penetrating Sealers (Silane/Siloxane) — Best for Ontario Concrete
Penetrating sealers are absorbed into the concrete rather than coating the surface. The two most common types are silane and siloxane (often combined in a "silane-siloxane" formula). These react chemically with the concrete to create a hydrophobic (water-repelling) zone within the concrete itself. From the surface, sealed concrete looks identical to unsealed concrete — there's no colour change, no sheen.
For Ontario's climate, penetrating silane-siloxane sealers are the preferred choice for several reasons:
- Invisible protection: They don't change the appearance, which most homeowners prefer for concrete driveways.
- No peeling: Because they become part of the concrete rather than coating it, there is no film to peel, blister, or chip.
- Breathable: They allow water vapour to escape from the concrete while preventing liquid water from entering — critical for concrete in freeze-thaw climates.
- Long-lasting: Quality silane-siloxane sealers can last 5–10 years.
- Salt resistance: They dramatically reduce chloride penetration, making them specifically valuable for driveways exposed to road salt.
Film-Forming Sealers (Acrylic, Polyurethane, Epoxy)
Film-forming sealers coat the surface of the concrete, creating a protective layer on top. Acrylic sealers are the most common and can create a shiny or wet-look finish. Polyurethane and epoxy sealers are harder and more chemical-resistant, used primarily for garage floors.
The limitations of film-forming sealers for outdoor driveways in Ontario:
- Peeling risk: Any surface coating can delaminate and peel when water gets beneath it — inevitable in freeze-thaw conditions.
- Slippery when wet: Shiny acrylic coatings reduce surface friction, creating a hazard on wet or icy driveways.
- Shorter lifespan outdoors: UV and traffic wear through surface coatings faster than penetrating sealers.
- Trapping moisture: A damaged film sealer can actually trap moisture in the concrete, worsening freeze-thaw damage.
"For concrete driveways in Kitchener-Waterloo, we almost always recommend penetrating silane-siloxane sealers. The invisible protection that allows concrete to breathe is exactly what this climate demands. A shiny acrylic looks nice for a year and then becomes a peeling problem."
— David, D&D Home Services Co-Founder
Surface Preparation for Concrete Sealing
As with all sealing projects, preparation determines results. Concrete has specific preparation requirements that differ from asphalt.
Cleaning
The surface must be thoroughly cleaned with a pressure washer to remove dirt, algae, mold, and debris. For driveways with significant organic growth or staining, a sodium hypochlorite solution followed by pressure washing is effective. Oil and grease stains require a concrete degreaser — standard driveway degreaser products work well on concrete.
Crack Repair
All cracks should be filled before sealing. For concrete, polyurethane caulk is the preferred crack filler — it bonds well to concrete and remains flexible through temperature changes. Concrete crack filler products (available in squeeze tubes or self-leveling pour versions) are suitable for horizontal surfaces. Allow fillers to cure fully before sealing.
Etching (When Required)
Very smooth, dense, or previously sealed concrete may need etching with a diluted muriatic acid solution to open up the surface pores enough for a penetrating sealer to work effectively. This step is typically done by professionals and requires appropriate safety precautions. Most standard driveways don't need etching — only very smooth trowel-finished concrete.
Complete Drying
Concrete must be completely dry before sealer application — at least 24 hours after cleaning, ideally 48 hours. Wet concrete will reject penetrating sealers and cause hazing or whitening in film-forming sealers.
Application Process for Concrete Sealer
Applying a penetrating silane-siloxane sealer to concrete is relatively straightforward but requires attention to detail.
- Apply with a pump sprayer: Flood the surface evenly, working in manageable sections. The goal is to saturate the surface without puddling.
- Work in sections: Avoid letting sealer dry on areas you haven't spread yet — it can create application marks.
- Back-roll or squeegee excess: After applying, use a roller or squeegee to spread any pooled sealer evenly and eliminate puddles.
- Apply a second coat while first is still damp: Penetrating sealers are typically applied in a "wet-on-wet" technique — the second application goes on while the first is still tacky but not fully dry.
- Keep foot traffic off for 4–6 hours; vehicle traffic for 24–48 hours.
Pro Tip: Apply concrete sealer in sections parallel to the direction of vehicle travel. This ensures any minor application variations run with traffic patterns rather than across them, making them far less visible.
Reapplication Timeline for Ontario Concrete
The appropriate reapplication frequency depends on the type of sealer used and the level of traffic and salt exposure.
| Sealer Type | Reapplication Frequency | Indicator for Resealing |
|---|---|---|
| Silane-siloxane penetrating | Every 5–10 years | Water no longer beads on surface |
| Acrylic film-forming | Every 2–5 years | Surface becomes dull, worn, or begins peeling |
| Polyurethane (typically garage use) | Every 3–7 years | Loss of gloss, surface wear |
New concrete should cure for a minimum of 30 days before any sealer is applied. Many contractors recommend waiting 60 days to allow thorough curing throughout the slab depth. Some penetrating sealers can be applied within 28 days, but always verify with the specific product's manufacturer guidelines.
Key Takeaways
- ✓ Ontario freeze-thaw cycles and road salt are the primary threats to concrete driveways — sealing is the best defense.
- ✓ Penetrating silane-siloxane sealers are the best choice for Ontario concrete driveways — invisible, breathable, and long-lasting.
- ✓ Avoid film-forming sealers (acrylic) on outdoor driveways in freeze-thaw climates — peeling risk is high.
- ✓ Never use rock salt on concrete, sealed or not — it accelerates chemical damage significantly.
- ✓ Surface prep is essential: clean, dry, and crack-filled before any sealer application.
- ✓ Silane-siloxane sealers last 5–10 years and can be tested with the water bead test.
For professional concrete and driveway sealing services in Kitchener-Waterloo, D&D Home Services uses the right products for Ontario's climate. Request a free quote today and protect your concrete before next winter.
