Sealer

What is a sealer?

A sealer is a protective coating that helps surfaces resist water, stains, dirt, and wear. It can soak into a material to reduce porosity (penetrating sealer) or sit on top as a thin film (film-forming sealer). Homeowners use sealers on wood, concrete, stone, tile, grout, and even asphalt to extend service life, make cleaning easier, and achieve a preferred look, from natural matte to a glossy wet look.

Where you’ll use a sealer at home

• Wood: decks, fences, furniture, trim, butcher blocks, and floors.
• Concrete and masonry: garage floors, driveways, patios, basement slabs, brick and block foundations.
• Stone and tile: natural stone countertops, pavers, backsplashes, showers, grout lines.
• Asphalt: driveways to refresh color and slow oxidation.
• Priming and stain blocking: as a primer-sealer before paint to lock down stains, odors, and tannins.

Types of sealers

Understanding the main categories will help you choose the right product.

By how they protect

• Penetrating sealers: Soak into the surface, reducing water absorption without leaving much, if any, film. Common chemistries include silane, siloxane, siliconate, and fluoropolymers. Great for brick, concrete, grout, and natural stone where you want a natural look and breathability.
• Film-forming sealers: Create a protective layer on the surface. Acrylics, polyurethanes, epoxies, and shellac fall here. These can change sheen, deepen color, and are often used where scrub resistance or a specific finish is desired.

By base

• Water-based: Lower odor, faster dry time, easier cleanup, often more breathable. Popular for interior use and many exterior applications.
• Solvent-based: Often richer color enhancement and longer open time. They can be more durable in some cases but come with stronger odor and higher VOCs.

Material-specific examples

• Wood sealers:
  • Penetrating water repellents and oils that protect against moisture and UV on decks and fences.
  • Sanding sealer for woodworking to fill pores and speed topcoat sanding.
  • Polyurethane (water- or oil-based) and spar urethane for durable topcoats; spar urethane flexes better outdoors.
  • Shellac for quick-drying sealer and odor blocker; not highly water-resistant on its own.
• Concrete and masonry:
  • Silane/siloxane penetrating sealers to shed water and salts.
  • Silicate densifiers to harden concrete and reduce dusting on interior slabs.
  • Acrylic sealers to enhance color on stamped concrete or pavers; available in matte to high-gloss.
  • Epoxy and polyurethane for chemical and abrasion resistance on shop and garage floors.
• Stone and tile:
  • Impregnating stone sealers for granite, marble, and porous tile that repel oils and water without changing appearance much.
  • Grout sealers to reduce staining in kitchens and baths.
• Asphalt driveway sealer: Coal tar alternatives or asphalt emulsion products to restore color and slow wear.
• Primer-sealers: Stain-blocking primers (shellac-, oil-, or water-based) that lock in nicotine, water stains, marker, and wood tannins before painting.

How to choose the right sealer

Ask a few quick questions:
- What is the surface? Wood, concrete, stone, tile, grout, or asphalt all benefit from different chemistries.
- Where is it located? Interior vs exterior, sun exposure, freeze-thaw cycles, and contact with water or de-icing salts.
- Do you want a natural look or color enhancement? Choose penetrating for near-invisible protection; choose film-forming for sheen or a wet look.
- Breathability needed? Exterior brick and many masonry walls need breathable sealers to let moisture escape and avoid damage.
- Slip risk? Glossy film-forming sealers can be slick when wet. Look for skid-resistant versions or add an anti-slip additive.
- Maintenance and recoat plan: Some acrylic film coats may need reapplication every 1–3 years; penetrating sealers can last longer but still require periodic checks.
- Odor and regulations: Water-based products often have lower VOCs and faster return-to-service.
- Special requirements: Food contact safety for butcher blocks, chemical resistance for garage floors, UV stability outdoors.

Application tips

• Prep is everything: Clean thoroughly, remove grease and soap scum, and let the surface dry. For concrete, consider etching or mechanical profiling if a film-forming sealer is planned. New concrete should cure about 28 days unless the product is labeled cure-and-seal.
• Moisture check: Sealing damp concrete or wood traps water and can cause clouding or peeling. Use the plastic sheet test on concrete or a moisture meter for wood if in doubt.
• Test a small area: Especially on stone and decorative concrete to confirm appearance and absorption.
• Right tools: Use a pump sprayer for penetrating sealers, a 3/8-inch nap roller or lambswool applicator for film coats, and a brush for edges and tight spots. Back-roll sprayed film coats for even coverage.
• Thin, even coats: Two thin coats beat one heavy coat. Avoid puddles and maintain a wet edge to prevent lap marks.
• Mind the weather: Apply between the manufacturer’s recommended temperature and humidity ranges. Avoid direct hot sun, rain, and dew for the stated window.
• Cure time and traffic: Respect recoat windows and cure times. Light foot traffic might be okay in 24 hours, heavy use or vehicle traffic could take several days.
• Maintenance: Clean with mild detergents, avoid harsh solvents unless compatible, and reapply based on water-bead tests or manufacturer guidance.

Common mistakes to avoid

• Using a non-breathable film on exterior brick or stone, which can trap moisture and cause spalling in freeze-thaw climates.
• Sealing wet surfaces: Leads to whitening, bubbles, or weak adhesion.
• Over-application: Thick coats can stay tacky, collect dust, or peel.
• Skipping surface prep: Dirt and oils block penetration and cause adhesion failures.
• Wrong product for the job: For example, countertop needs an impregnating oil- and water-repellent, not a soft acrylic floor sealer.
• Incompatible recoats: Applying a solvent-based sealer over a water-based film (or vice versa) without proper prep can cause lifting. Strip or abrade as directed.
• Confusing sealer with sealant: A sealer is a coating; a sealant (caulk) fills gaps and moves with joints.

Related terms

• Sealant/caulk: Flexible material for gaps and joints.
• Finish/topcoat: The final protective layer on wood or floors.
• Primer-sealer: Paint primer that locks stains and improves adhesion.
• Densifier: Chemical treatment that hardens concrete.
• Waterproofing membrane: Sheet or liquid-applied barrier used behind tile or on foundations.
• Stain: Colorant that may need a separate sealer or topcoat.

Practical examples

• Sealing a cedar deck: Clean with a deck cleaner, rinse, and let dry 24–48 hours. Choose a penetrating water-repellent with UV inhibitors in a natural or lightly tinted tone. Apply with a pad or brush, working two boards at a time end-to-end to avoid lap marks. Wipe excess within a few minutes to prevent sticky spots. Recheck yearly; recoat when water no longer beads.

• Garage floor protection: For low maintenance and salt resistance, use a penetrating silane/siloxane on cured, clean, and dry concrete. Spray and back-roll, then keep cars off the slab for at least 24–48 hours. For a brighter, wipeable surface, consider a two-part epoxy with a urethane topcoat, but do proper profiling and moisture testing first.

• Shower grout sealing: After grout cures per instructions, clean and dry the lines. Apply a penetrating grout sealer with a small brush or applicator bottle, wait the dwell time, then wipe tile surfaces dry. Repeat if the grout darkens quickly during a water test.

• Granite countertop: Perform a water and cooking oil drop test. If darkening occurs within minutes, use an impregnating stone sealer. Apply, allow dwell per label, and buff completely dry to avoid hazing. Retest in a day; reapply only if needed.

A good sealer match brings easier cleaning, fewer stains, and a finish that suits your space. Take time to prep, choose for your surface and conditions, and follow the label, and your results will last.