How to Seal Concrete (Step-by-Step Guide)
Sealing concrete is one of the easiest ways to extend its lifespan and improve its appearance. A quality sealer protects against water penetration, staining, freeze-thaw damage, and UV fading. The application process is straightforward—even beginners can achieve professional results with proper preparation.
How to Seal Concrete (Step-by-Step Guide)
Sealing concrete is one of the easiest ways to extend its lifespan and improve its appearance. A quality sealer protects against water penetration, staining, freeze-thaw damage, and UV fading. The application process is straightforward—even beginners can achieve professional results with proper preparation.
The key is timing: new concrete needs 28 days to cure before sealing, and surface preparation accounts for 80% of a successful seal job.
Why Seal Concrete?
Unsealed concrete is porous—water, oil, and contaminants penetrate the surface over time.
| Protection Against | How Sealer Helps |
|---|---|
| Water damage | Creates barrier against penetration |
| Freeze-thaw cycles | Prevents water absorption that causes spalling |
| Staining | Blocks oil, grease, and chemical penetration |
| UV fading | Protects colored/stained concrete |
| Dusting | Hardens surface, reduces powder |
| Efflorescence | Limits moisture movement that causes white deposits |
Sealed concrete lasts longer, looks better, and requires less maintenance than unsealed concrete.
When to Seal: The 28-Day Rule
For new concrete, wait at least 28 days before applying sealer.
Why the wait matters:
- Concrete continues curing and releasing moisture for weeks
- Sealing too early traps moisture, causing whitening, bubbling, or peeling
- The surface needs to reach full strength before sealing
| Concrete Age | Ready to Seal? |
|---|---|
| 7 days | No—still curing rapidly |
| 14 days | No—too much moisture |
| 21 days | Possibly in dry climates |
| 28 days | Yes—standard recommendation |
| 30+ days | Ideal |
For existing concrete: Seal anytime, as long as the surface is clean, dry, and in good condition.
Types of Concrete Sealers
Choose your sealer based on desired appearance and protection level:
Penetrating Sealers (Recommended for Beginners)
What they do: Absorb into concrete, react chemically to fill pores from within.
| Type | Best For | Appearance |
|---|---|---|
| Silane/Siloxane | Driveways, exterior | Natural (no change) |
| Siliconate | Vertical surfaces | Natural |
| Silicate (densifier) | Garage floors, interior | Natural |
Pros: Easy to apply, won't peel or flake, breathable, long-lasting (5-10 years) Cons: No gloss, doesn't enhance color significantly
Film-Forming Sealers
What they do: Create a protective coating on the surface.
| Type | Best For | Appearance |
|---|---|---|
| Acrylic | Decorative concrete, patios | Gloss or matte |
| Polyurethane | High-traffic, interior | High gloss |
| Epoxy | Garage floors, industrial | High gloss |
Pros: Enhances color, provides gloss, excellent stain protection Cons: Can peel if moisture issues, requires reapplication every 2-3 years, can be slippery
Which Should You Choose?
| Situation | Recommended Type |
|---|---|
| Driveway (basic protection) | Penetrating silane/siloxane |
| Stamped/colored patio | Acrylic (semi-gloss) |
| Garage floor | Penetrating densifier or epoxy |
| Pool deck | Penetrating (non-slip) |
| First-time DIYer | Penetrating (most forgiving) |
Surface Preparation
Proper prep is the difference between a sealer that lasts years and one that fails in months.
Step 1: Clean Thoroughly
The surface must be completely clean:
- Sweep to remove loose debris
- Pressure wash at 2,500-3,000 PSI (let dry 24-48 hours after)
- Remove stains: Use concrete degreaser for oil, rust remover for rust stains
- Remove old sealer: Strip or etch if previous sealer is peeling
Step 2: Repair Damage
- Fill cracks with concrete crack filler
- Patch spalled areas with resurfacing compound
- Let repairs cure fully before sealing
Step 3: Test for Moisture
Tape a plastic sheet (2×2 ft) to the concrete. Wait 24 hours. If moisture appears underneath, the concrete is too wet to seal.
Step 4: Test for Existing Sealer
Sprinkle water on the surface. If it beads up, there's existing sealer that may need removal. If it absorbs, you're ready to proceed.
Step 5: Ensure Proper Conditions
| Factor | Requirement |
|---|---|
| Temperature | 50-90°F |
| Surface temp | Not hot to touch |
| Weather forecast | No rain for 24 hours |
| Surface | Completely dry |
Application Process
Tools Needed
- Pump sprayer (for penetrating sealers) OR
- Roller with 3/8" nap (for film-forming sealers)
- Paint tray
- Brush for edges
- Tape for adjacent surfaces
- Safety: glasses, gloves, respirator for solvent-based
Step-by-Step Application
For Penetrating Sealers:
- Pour sealer into pump sprayer
- Apply first coat in even, overlapping passes
- Work in sections (10×10 ft areas)
- Back-roll puddles to ensure even coverage
- Wait 30-60 minutes for first coat to absorb
- Apply second coat (optional but recommended)
- Allow 24-48 hours to cure before foot traffic
For Film-Forming Sealers:
- Pour sealer into paint tray
- Cut in edges with brush
- Apply thin, even coats with roller
- Maintain wet edge to avoid lap marks
- Apply in one direction for consistent appearance
- Wait 2-4 hours between coats
- Apply 2-3 thin coats (better than one thick coat)
- Allow 24-72 hours before traffic
Coverage Rates
| Sealer Type | Coverage |
|---|---|
| Penetrating | 150-300 sqft per gallon |
| Acrylic | 200-400 sqft per gallon |
| Epoxy | 200-300 sqft per gallon |
How Often to Reseal
| Sealer Type | Reseal Frequency |
|---|---|
| Penetrating silane/siloxane | Every 5-10 years |
| Penetrating silicate | Once (permanent) |
| Acrylic | Every 2-3 years |
| Polyurethane | Every 2-4 years |
Signs it's time to reseal:
- Water no longer beads on surface
- Color enhancement has faded
- Surface seems more porous
- Staining happens more easily
Common Sealing Mistakes
Applying Too Thick
Problem: Film-forming sealers bubble, peel, or turn white when applied too heavily.
Fix: Apply thin coats. Two thin coats outperform one thick coat.
Sealing Wet Concrete
Problem: Trapped moisture causes whitening, cloudiness, or adhesion failure.
Fix: Ensure surface is bone dry. Wait 24-48 hours after rain or pressure washing.
Sealing Too Soon
Problem: New concrete still releasing moisture causes sealer failure.
Fix: Wait full 28 days for new concrete.
Skipping Surface Prep
Problem: Sealer won't bond to dirty, oily, or previously sealed surfaces.
Fix: Clean thoroughly. Strip old sealer if necessary.
Frequently Asked Questions
How long after pouring can I seal concrete?
Wait at least 28 days for new concrete. This allows proper curing and moisture release. Sealing too early traps moisture, causing the sealer to whiten, bubble, or peel.
Is concrete sealer worth it?
Yes. Sealing extends concrete lifespan by protecting against water damage, freeze-thaw cycles, and staining. The cost ($0.15-0.50 per sqft for DIY) is minimal compared to repair or replacement costs. It's especially important for decorative concrete.
How often should you reseal concrete?
Penetrating sealers last 5-10 years. Film-forming sealers (acrylic, polyurethane) need reapplication every 2-3 years. When water stops beading on the surface, it's time to reseal.
Can you seal old concrete?
Yes—and you should. Clean the surface thoroughly, repair any damage, and apply sealer. Old concrete often benefits more from sealing than new concrete because it's more porous from weathering.
Key Takeaways
- Wait 28 days before sealing new concrete
- Surface prep is 80% of a successful seal job
- Penetrating sealers are easiest for beginners
- Thin coats work better than thick ones
- Reseal on schedule to maintain protection
Sealing helps prevent concrete cracking and damage by keeping moisture out. Combined with proper curing (see curing guide), sealing is your best investment in concrete longevity.