Should Concrete Be Sealed?

1. The Short Answer: Sealing Is About Water

Concrete is porous. A cured slab is full of fine capillaries that draw in water, and with the water come dissolved salts, oils and anything else spilled on it. Most of the damage homeowners see on exterior concrete, from flaking and pitting to dark oil ghosts and white mineral bloom, starts with something soaking in. A sealer either lines those pores so liquid cannot enter, or covers the surface with a film so liquid never reaches the pores. That is the whole job.

Whether that job is worth doing depends on how much harm water can do to your particular slab. In a cold climate where water freezes inside the surface every winter and road salt is tracked onto the driveway, it can do a lot. The National Ready Mixed Concrete Association's guidance on scaling, which draws on the American Concrete Institute's Guide to Durable Concrete, specifically recommends protecting new slabs from saturation before winter by applying a breathable silane or siloxane sealer. In a dry, frost-free climate, the same water mostly evaporates again and does very little.

So the honest answer to whether concrete should be sealed is: exterior concrete in freeze-thaw country usually should, decorative concrete almost always should, and plain concrete in a mild climate does not have to. Sealer does not make bad concrete good. Well-made, air-entrained concrete with a proper cure tolerates a lot unsealed; poorly made concrete will eventually fail sealed or not. Sealer buys margin, and the question is how much margin your slab needs.

2. When Sealing Concrete Is Worth It

Freeze-thaw climates and deicing salt

This is the strongest case for sealing. Water expands as it freezes, and when the top layer of a slab is saturated, repeated freezing breaks the surface paste away in shallow flakes, a failure called scaling. Deicing salts make it worse by keeping the surface wetter and increasing the number of freeze-thaw cycles. NRMCA's guidance is blunt: do not use deicing salts on concrete in its first year, and protect new slabs from saturation with a breathable sealer. Our guide to whether salt damages concrete covers the mechanism and the deicers to avoid.

A penetrating sealer is the right tool here because it reduces how much water and brine the surface absorbs while still letting vapour escape. It does not stop scaling on concrete that was badly finished or not air-entrained, but on sound concrete it reduces the wetting that drives the damage. Driveways, front walks, garage aprons and steps are the priority surfaces, since they get the most salt and the most traffic.

Stains: driveways, patios and outdoor kitchens

Oil drips, barbecue grease, rust from furniture, leaf tannins and red wine all wick into bare concrete and become very hard to lift once they are in. A sealed surface gives you time to clean a spill before it soaks in. Film-forming sealers hold stains on the surface best; penetrating sealers repel water-based spills well and slow down oils without stopping them entirely. If your driveway already carries old oil marks, clean those first, as our guide to getting oil out of concrete explains, because sealing over them locks them in.

Decorative, coloured and stamped concrete

Stamped, integrally coloured, stained and exposed-aggregate concrete are built on the assumption that they will be sealed. The sealer protects the colour from wear, helps it resist UV dulling, and on stamped work usually provides the enhanced, slightly wet look that makes the pattern read properly. Leaving a stamped patio unsealed tends to make it look chalky within a few seasons. For that category, the question is not whether to seal but which sheen; our Armor AR350 vs AR500 comparison walks through one common low-gloss versus high-gloss decision.

Pavers

Concrete pavers are a special case: sealing is optional for structural reasons but common for appearance and joint stability, and some products are designed to harden joint sand as well as protect the surface. Our guide to whether pavers need to be sealed covers that decision separately, because the answer depends on the paver type, the joint material and the look you want.

3. When Sealing Is Optional, or Not Worth It

In a frost-free climate, a plain grey slab that never sees deicing salt has very little to gain structurally from sealer. Water still soaks in when it rains, but it evaporates again without freezing, and good concrete is not harmed by getting wet. If the slab is a utility surface such as a side path, a bin pad or a shed base, and you are not bothered by the odd stain, leaving it bare is a perfectly reasonable decision. You will not shorten its life in any meaningful way.

Sealing is also not a repair. It does not close structural cracks, level a settled slab, restore a surface that is already badly scaled, or stop water coming up from wet ground underneath. A slab with widespread flaking needs its loose material removed and a resurfacer applied before sealing makes sense, as covered in our concrete resurfacer guide. A slab with a moisture problem from below is a poor candidate for a film-forming sealer, because trapped vapour can blush and lift the film; if you seal it at all, a breathable penetrating product is the only sensible choice.

There are surfaces where a film can make things worse. A glossy acrylic on a shaded, north-facing walk that stays damp, or on a pool deck, adds slip risk unless non-slip grit is mixed in. An interior slab that will be covered with tile, vinyl or carpet should not be sealed without checking the flooring adhesive maker's requirements, because many adhesives need bare, porous concrete to bond. In those cases, the right answer may be a penetrating sealer or no sealer at all.

Finally, consider the maintenance you are signing up for. A penetrating sealer is close to invisible and needs reapplying every several years. An acrylic film needs a clean-and-recoat on a much shorter cycle and must be kept compatible with what is already on the slab. If you know you will not keep up with recoats, a worn, patchy acrylic can look worse than bare concrete. Our concrete sealer cost guide helps put a price on both paths before you start.

4. The Water-Drop Test: Is Your Concrete Already Sealed?

Before deciding anything, find out what is already on the slab. Sprinkle or pour a little clean water on several spots, including a high-traffic area, a protected corner and anywhere that looks different from the rest. Watch for a minute or two. On bare, unsealed concrete the water darkens the surface and soaks in quickly. On concrete with a working sealer it beads or sits on top, and the concrete underneath barely changes colour.

Read the result spot by spot. If water beads everywhere, the slab is still protected and does not need sealing yet. If it soaks in everywhere, the slab is unsealed or the old sealer has worn out. If it beads in corners but soaks in along tyre tracks and walking paths, an old sealer is wearing through in the traffic areas, and that is the usual moment to reseal. Our guide to how long concrete sealer lasts uses the same test to set a resealing schedule.

The test also tells you which kind of sealer is present, which matters because new sealer must be compatible with old. A penetrating sealer beads water but leaves no visible sheen or film. An acrylic leaves a sheen you can see from a low angle, and a little xylene on a rag will make it go tacky. If you find a film, the next coat generally has to be the same chemistry; Foundation Armor, for example, says its solvent-based acrylics go only over bare concrete or an existing solvent-based acrylic, and that water-based acrylics should be resealed with water-based acrylics.

A dense, power-trowelled surface can fool the test, because it absorbs slowly even when bare. If water sits on a slab you are confident has never been sealed, the surface may be too tight for a sealer or stain to penetrate. Behr's instructions for its concrete stain use the same check, saying that if water is not quickly absorbed the surface should be etched again. A light acid etch or a grind opens the pores. Separately, if you suspect moisture is coming up from below, tape a square of clear plastic to the slab overnight; condensation underneath means wait, or choose a breathable product.

5. Penetrating or Film-Forming: Picking the Right Kind

If you decide to seal, the next decision is what kind of sealer, and it matters more than the brand. Penetrating sealers such as silanes and siloxanes soak into the pores and react to form a water-repellent lining. They do not change the look of the concrete, they let vapour escape, and because nothing sits on the surface there is nothing to peel, scuff or make slippery. Film-forming sealers, mostly acrylics, cure into a thin layer on top that darkens and enhances the colour, adds sheen and holds stains on the surface.

The lifespans are very different. Foundation Armor's own guidance is that concrete sealed with a silane-siloxane needs resealing every 5 to 7 years, while an acrylic sealer needs resealing every 6 months to 3 years depending largely on climate. Our acrylic vs penetrating sealer comparison lays out the trade-offs in full, but the short version is that penetrating sealers win on protection per dollar and film-formers win on looks.

Once you choose, you are partly committed. A penetrating sealer cannot be removed from the pores, and an acrylic will not bond to a surface that is still actively water-repellent, so moving from penetrating to film-forming means waiting until the repellency has worn off. Going the other way means stripping the film completely first. For most plain driveways and walks the penetrating route is the one we would pick; our best concrete sealer guide ranks products in both families by application.

6. How to Seal New Concrete: Timing Comes First

New concrete is not ready for most sealers on the day the forms come off. It needs time to gain strength and, just as importantly, to dry, because fresh concrete gives off water for weeks. A film-forming sealer applied too early traps that moisture and turns cloudy or loses adhesion. The common rule on sealer labels is about 28 days: Foundation Armor's AR350 data sheet, for example, says concrete must be a minimum of 28 days old, and Behr's concrete stain label asks for at least 30 days of cure. Always follow the specific product's label, which is the instruction that governs its warranty.

Freeze-thaw climates add a second clock. NRMCA's guidance on scaling says not to use deicing salts such as calcium or sodium chloride in the first year after placing concrete, to use clean sand for traction instead, and to protect new slabs from becoming saturated before winter with a silane or siloxane breathable sealer applied to reasonably dry concrete, noting that late summer is the ideal time for that treatment. A slab poured in spring or early summer can be cured, dried and sealed before the first frost. A slab poured in late autumn often cannot, which is one reason late-season pours scale more often.

There is one exception to the wait: cure-and-seal products, which contractors spray or roll on right after finishing to slow evaporation and help the concrete cure. They count as a light first coat on some jobs, but they are not a substitute for a proper sealer later, and some must be removed or allowed to wear off before a different sealer will bond. Ask your contractor what, if anything, went on the slab, and keep the product name. Our guide to how long concrete takes to cure covers the full timeline from walking on it to driving on it.

When the slab is old enough, the method is simple. Sweep and rinse it, let it dry for at least a day of good weather, check the forecast for a dry window, and apply the sealer in thin, even coats at the temperatures on the label. Penetrating sealers are usually flooded on until the surface stops absorbing and then the excess is spread out; film-formers go on in two thin coats with a roller or sprayer. Keep cars off for the time the label specifies, which for many acrylics is about 48 hours.

7. Sealing an Old Concrete Driveway: Is It Too Late?

It is rarely too late. An older driveway that has never been sealed is often a better candidate for a penetrating sealer than a new one, because years of weathering have opened its surface and it has finished drying and shrinking. What decides whether sealing is worthwhile is the condition of the surface. Sound concrete with some cracks and stains is worth sealing. Concrete that is flaking over large areas needs repair first, because sealer will not hold loose paste in place.

Start with the water-drop test to find out whether there is old sealer on it, then clean thoroughly. Degrease oil spots individually before washing the whole surface, fill cracks with a flexible concrete crack filler, and let everything dry fully. If the test showed a worn acrylic film, you either recoat with a compatible acrylic or strip it before switching to a penetrating product. Our dedicated guide to sealing old concrete covers assessment and stripping in detail.

For the application itself, our step-by-step on how to seal a concrete driveway covers tools, coverage and curing. The timing rules are the same as for any exterior sealing job: a dry surface, a dry forecast, and temperatures within the label range, which for many products means avoiding cold autumn evenings and hot midday sun. Sealing before winter is better than sealing after it, because the point is to reduce how much water the slab absorbs before it starts freezing.

Is sealing an old driveway worth the money? If you live where it freezes and you use any deicer, almost certainly, because the cost of a penetrating sealer is small next to resurfacing or replacing a scaled driveway. If you live somewhere mild and the driveway is sound and you do not mind its stains, sealing is optional. In both cases, do the water test once a year and reseal when the traffic lanes stop beading, rather than on a fixed calendar.