How to Seal a Concrete Floor

Does your floor need sealing?

It depends on where the slab is and what goes on top. For exterior slabs exposed to deicers, the National Ready Mixed Concrete Association's scaling guide suggests you "consider sealing the surface with a commercial breathable sealer," meaning a silane or siloxane. If the slab will be covered, check with the flooring maker first: ASTM F710 wants a floor for resilient flooring "free of substances that may prevent adhesive bonding."

Topical vs penetrating sealers

How long sealers last

The Decorative Concrete Council's sealer selection guide gives recoat intervals of 1 to 2 years for water-based acrylics, 1 to 3 for solvent-based acrylics, 2 to 4 for acrylic thermoplastics and 2 to 5 for cure and seals. Penetrating silanes last much longer: an Oklahoma DOT study found a silane layer deeper than the specified 1/8 inch on 100 percent of sampled bridges aged 6 to 12 years, about 67 percent at 15 years, and 16 to 21 percent at 17 to 20 years.

Cure and seal: C309 vs C1315

A "cure and seal" goes on fresh concrete to hold water in while it cures, then stays on as a sealer. Check which standard is on the label:

Scope wording is from ASTM's C309 and C1315 pages; the water limit is from FHWA, which notes C1315 may need about 25 percent solids. If it says C309 only, plan to seal again later. C1315 rates yellowing in classes from non-yellowing to unrestricted, so pick a non-yellowing one for floors in the sun. Curing itself is covered in the concrete cure time guide.

Water-based or solvent-based

VOC rules decide what you can buy

The federal limit in 40 CFR Part 59 depends on the category a maker declares: 700 g/L for concrete curing and sealing compounds, 600 for waterproofing sealers, 400 for floor coatings and sealers. Some regions are far stricter. Southern California's South Coast AQMD Rule 1113 caps waterproofing concrete and masonry sealers at 100 g/L and floor coatings at 50, so a product sold in one state may be reformulated or unavailable in another.

Gloss and grip

Look: film sealers deepen color and add sheen. The Council's stamped concrete best practice notes that most penetrating sealers don't enhance color. Nobody publishes how much a sealer will darken your slab, so seal a test patch first.

Grip: a glossy film gets slick when wet. The Council tells you to meet "ASTM 2047 standards for slip resistance," but ASTM D2047 is a dry, static test for polish-coated floors and is "not intended for use on 'wet' surfaces." The tile benchmark for wet floors is ANSI A326.3, which calls for a wet dynamic coefficient of friction of 0.42 or more for level interior floors that get walked on wet.

• Add grit to the last coat on steps, pool decks, ramps and anything that gets wet. Use an anti-slip additive made for your sealer type, at the dose on its label.
• Not sand. The Council warns "adding sand and some silica materials is not recommended and can actually cause sealer deterioration."
• How much: exterior public walkways should have enough "that it can be felt with a bare hand."

When to seal new concrete

Let it cure, then let it dry. The Decorative Concrete Council cites ACI's guidance of about 7 days of curing above 40°F (3 days for high-early-strength concrete at 73°F or warmer), then a wash and 12 to 24 hours of drying before sealing. Some sealer labels ask for more: Sika's Sikagard H 1001 silane wants concrete at 80 percent of design strength, which it says is typically reached in 14 to 28 days. Follow the label for the product you buy.

The weather window

• Temperature: water-based 45°F and rising, up to 90°F. Solvent-based down to 40°F.
• Humidity: below 70 percent RH.
• Rain: "Do not seal a surface when rain or condensation is expected within 12 hours."
• Sun and wind: skip direct sun and wind with solvent-based sealers.
• Time of day: seal when "the slab temperature will be falling for 3 to 4 hours after application," usually late afternoon or evening.

How to seal a concrete floor, step by step

1. Clean the slab completely. Scrub off dirt, grease and dust with a concrete degreaser and rinse. Outdoors, the Council recommends power washing at a minimum of 3,500 psi, then 12 to 24 hours of drying.
2. Strip anything already on it. "Any residual curing compounds need to be chemically stripped or mechanically removed before sealing." Grinding or shot blasting is the reliable route.
3. Let it dry fully. At least a day after washing, longer in a damp space. Sealing over trapped moisture causes clouding, blisters and peeling.
4. Repair and etch. Patch cracks (see floor repair). Etch very smooth, hard-troweled concrete so the sealer can grip; Eagle's coverage chart marks smooth troweled concrete "etch required."
5. Test for moisture. Tape an 18 by 18 inch sheet of plastic to the floor for at least a day, the ASTM D4263 plastic sheet test as Tnemec describes it. Darkening or condensation underneath means don't seal yet. A dry result doesn't prove the slab is dry, only that the surface is.
6. Apply thin coats. Cut in the edges with a brush, then spray and back-roll. The Council calls spray-and-back-roll "the preferred application method" and says dip-and-roll leads "to uneven and excessive applications." Two thin coats beat one heavy one.
7. Recoat and cure. Wait the recoat time on the label, apply the second coat at a right angle to the first, then keep traffic off for the full cure time the label gives.

How much sealer to buy

Coverage depends on surface texture more than anything. Eagle's chart for its Gloss Coat acrylic is net for two thin coats:

• Smooth troweled etch first

  300

  sq ft per gallon

• Broom finish

  200

  sq ft per gallon

• Stamped or textured

  200

  sq ft per gallon

• Exposed aggregate or pavers

  100

  sq ft per gallon

Gallons = floor area (sq ft) ÷ coverage per gallon

Example: a 20 by 20 foot broom-finished garage is 400 sq ft. At 200 sq ft per gallon that's 400 ÷ 200 = 2 gallons for two coats. The same floor smooth troweled needs 400 ÷ 300 = 1.3, so buy 2 gallons there too. Other products vary: Brickform's solvent acrylic Gem-Seal lists 250 to 350 sq ft per gallon. Use the number on your own label, and get the area from the square footage calculator. What a contractor charges is in the concrete floor cost guide.

Is it sealed, and when to reseal

The water drop test. Put a few drops of water on the floor in several spots. If they soak in and darken the concrete, it's bare enough to seal. If they bead up and sit there, something is still repelling water. The test won't tell you which sealer is on the floor, and that matters for recoating.

Reseal when it needs it, not on a calendar. The Decorative Concrete Council's 2025 stamped concrete best practice says reseals "should be performed on an 'as needed' basis rather than at a set number of years," triggered by lost water and stain repellency or faded color. Its older sealer selection guide gives a rough schedule: every 2 to 3 years for high-traffic and sunny areas, 4 to 5 for interior floors. Don't overdo it: "Applying sealer too thick or applying too many coats will affect breathability and bond." To bring back shine without adding film, the Council says a solvent wipe works better than another coat.

When sealing goes wrong

Sealing stamped concrete

The Decorative Concrete Council's 2025 best practice for sealing stamped concrete sets out the method:

• Sealer: "topical film-forming sealers are the most used option for stamped concrete projects due to their color-enhancing properties," usually acrylics.
• Prep: power wash at 3,500 psi or more, then let the slab dry 12 to 24 hours.
• Timing: after about 7 days of curing above 40°F, unless your sealer's label asks for longer.
• Application: spray and back-roll thin coats as the slab cools. Add a grit additive on steps, pool decks and sloped drives (see gloss and grip).
• How often: as needed, when water stops beading or the color fades, not every year.

Pattern choices are in stamped concrete patterns, and costs, including sealing, are in stamped concrete cost.

Basement and garage floors