How do I clean and reseal stamped concrete?

Wash the stamped concrete thoroughly, let it dry for about a day, then roll or spray on one thin, even coat of a sealer that is compatible with the one already there, at the coverage rate on the label, in shade and mild weather. The hard part is not the sealing. It is the cleaning, the drying and resisting the urge to put on too much.

When stamped concrete needs resealing

Reseal when the surface needs it, not after a set number of years. One manufacturer's water-based sealer calls for a light maintenance coat every 1 to 2 years depending on the concrete's exposure to traffic, abrasion and weathering,^[2] which is a range, not a schedule. Resealing too often does harm: the same maker warns that too many successive coats, or multiple coats over time can cause bubbling, whitening, peeling, and ultimate failure of the product,^[1] and says a buildup of sealer applied numerous times over the years traps moisture under the film.^[3]

Two quick checks tell you where you stand. Sprinkle water on a few spots: on well-sealed concrete it usually beads, and on worn sealer it soaks in and darkens the surface. Then look at the color in daylight. If it looks chalky or flat but deepens when wet, the sealer is probably wearing thin.

As a rough guide, the surface of one professional solvent-based acrylic sealer typically begins to dull after 3 to 4 years of use,^[1] while a water-based version from the same maker calls for a light maintenance coat every 1 to 2 years.^[2] Sun, foot traffic, cars and winter salt all shorten that.

Choose products made for the job, and for you

Many of the sealers, cleaners and grit additives decorative contractors use are professional products. Three named on this page as examples, Increte Clear Seal, Euco R&E Cleaner and Increte Shur-Grip, are each labelled "For professional use only."^[1][5][6] They show the kind of rules a sealer label sets. For your own reseal, buy a product sold for homeowner use, and follow its label rather than the figures here.

Solvent-based sealers need the most care. Clear Seal, a solvent-based acrylic, carries the signal word "Danger" and is classed as a flammable liquid.^[4] Its hazard statements include "Harmful if inhaled", "May cause cancer", "May cause genetic defects" and "May be fatal if swallowed and enters airways".^[4] Its precautions call for protective gloves and clothing, eye or face protection such as safety glasses with side shields or goggles, and a suitable respirator if ventilation is inadequate.^[4] They also call for not breathing its vapor or spray, using it only outdoors or somewhere well ventilated, and keeping it away from heat, sparks, open flames and other ignition sources, with no smoking.^[4]

In practice that means no grill, cigarette or running engine nearby, windows on the house side closed, and children and pets kept indoors until it dries. If the solvent odor is objectionable, the maker's advice is to switch to a water-based, low-odor product.^[1] A water-based sealer has its own safety data sheet, to be read before use.^[2]

Find out what is on it now

Before you buy anything, find out what sealer the installer used. The original sealer's manufacturer or a local supplier can tell you what is compatible with it. Some products have strict rules: Clear Seal, for example, should not go over other curing compounds, and old water-based sealers must be removed before it goes on.^[1] If nobody knows what is on the slab, a test patch is not optional. If the only compatible sealer turns out to be a solvent-based professional product, that is a good point to hand the job to a decorative concrete contractor.

Cleaning comes first

For routine care, clean as needed with mild soap or detergent and water, then rinse.^[1] Before a reseal, the job has to be more thorough. One solvent-based sealer's label says the surface must be clean and free of puddled or standing water,^[1] and a water-based one calls for concrete free of dust, dirt, laitance, efflorescence, curing compounds, paint, oil, grease and other contaminants.^[2] Older concrete should be cleaned with a cleaner/degreaser specifically designed for concrete and paver surfaces.^[2] Scrub with detergent and a stiff brush, work into the grout lines, and rinse until the water runs clear.

A pressure washer is optional. Held too close it can etch the surface or strip the darker accent color from the grout lines, so the brush-and-hose method is slower but safer if you have not run one before.

Oil and white haze need their own treatment. Many efflorescence cleaners are acids. Euco R&E Cleaner, a professional example, removes primary and secondary efflorescence and is safe on integrally colored concrete,^[5] but it contains phosphoric acid and calls for rubber gloves and eye protection.^[5] Whatever you use, follow the label exactly and rinse well.

Then dry the slab properly: use a leaf blower to clear standing water from the slab and the joints, and give it time before sealing. Sealer over trapped water is a common reason a fresh coat turns white.^[3]

Pick the weather and the time of day

Read the temperature limits on your product. Clear Seal, for example, is not to be applied when the concrete or air is below 40 °F, or if rain is expected within 12 hours, and hot, direct sunlight or temperatures above 95 °F can cause bubbling.^[1] Its water-based counterpart lists an application range of 45 to 95 °F and no rain or heavy fog for 8 to 12 hours.^[2]

In a Virginia summer, sun on the slab is often the bigger problem. Seal in the evening or in shade rather than with the sun on the slab. Spring and fall days with dry air are often easier.

Applying the sealer

Thin is the goal. Coverage rates vary by product: the water-based Clear Seal lists 200 to 300 ft² per gallon,^[2] and the solvent-based one says to measure the area to be sealed and the corresponding volume of product required based on the coverage rate.^[1] Measure the patio, divide by the label's rate, and pour out only what that area should take.

Both Euclid sealers named here can be applied with a sprayer or a roller, and the solvent-based one calls for an industrial, hand-held, pump-up or airless sprayer, or by roller, not a plastic garden-type sprayer.^[1] For a more uniform appearance over decorative concrete, the water-based one says it is recommended to backroll the product after spraying:^[2] mist the sealer on, then roll it out so it does not pool in the texture. The solvent-based sealer lists a first coat at 300 square feet per gallon and a second at 400,^[1] and calls for a short, 3/8-inch nap, solvent-resistant roller.^[1] On a reseal, one coat is often enough.

Then keep everyone off it. Clear Seal, for example, lists 4 to 6 hours before foot traffic and 6 to 10 hours before wheel traffic, results developed under laboratory conditions, and low concrete or air temperature or high relative humidity extends its drying time.^[1] Your own product's label sets the times to follow.

A Virginia rule to know. In the Northern Virginia, Fredericksburg and Richmond Volatile Organic Compound Emissions Control Areas,^[7] state air rules cap the VOC content of architectural coatings by category. The caps include 400 grams per liter for waterproofing concrete and masonry sealers and 350 grams per liter for concrete curing compounds,^[8] and a coating labelled or recommended for more than one category is held to the most restrictive of those limits.^[8] Clear Seal, which is sold as a curing compound and a cure and seal, lists a VOC content of 681 grams per liter.^[1] If you live in one of those areas, check the VOC figure on the label against the limit for every category the product is sold for.

If the old sealer is white, peeling or thick

White, cloudy sealer on a solvent-based acrylic has two main causes: applying it to a wet surface or applying it too thick.^[3] A film that simply went on too heavy can sometimes be rescued without adding sealer, but the rescue is solvent work (see the next section). Sealer that is loose, flaking or badly discolored has to come off before resealing: one manufacturer says all old paint, oil, grease and water-based sealers must be removed and sells a coating stripper for it.^[1] That is usually a job for a decorative concrete contractor. If the patio is slick when wet, see how to keep stamped concrete from getting slippery before you reseal, and if the color itself is going, see why stamped concrete fades.

Stop and call a pro if

• New sealer went on too thick and turned white or cloudy. On a solvent-based acrylic, the fix is that scrubbing with a solvent such as xylene turns the sealer back into a liquid so the excess can be wiped off, with no new sealer added.^[1] That is solvent work across the whole slab, best left to a contractor equipped for it.
• The old sealer is peeling, flaking or white across large areas. Stripping it takes blasting equipment or chemical strippers.
• The only compatible sealer is a solvent-based product labelled for professional use.
• The surface is scaling, spalling or cracked. Sealer will not fix a failing surface, and a repair needs to be planned before any reseal.
• You cannot identify the old sealer and the test patch fails. A contractor can test and strip as needed.
• The color is uneven or washed out and you want it restored, which can mean a tinted sealer or stain that is hard to get even.
• It is a large driveway or a pool deck, where an uneven coat or the wrong additive costs more to fix than to do right.

Getting help in Virginia

Loclis lists DPOR-licensed businesses with their licence number and class. Browse stamped and decorative concrete, look up concrete contractors in Blacksburg, or read more concrete and hardscaping answers, including what stamped concrete costs in Virginia.

Describe the reseal once and licensed local concrete businesses quote it.