To remove concrete sealer, first work out what type it is, then strip a film-forming sealer with a stripper made for it or grind it off. Penetrating sealers sit inside the concrete and usually cannot be stripped. Only strip when the sealer is peeling, cloudy, yellowed or the wrong type, and let the slab dry fully before resealing.
In This Article
- When you need to remove concrete sealer, and when you do not
- Step 1: Identify the sealer you have
- How to strip concrete sealer: the main methods compared
- How to remove a film-forming sealer with a chemical stripper
- Grinding, blasting and the dust problem
- Prepare the slab to reseal in Ontario
- When to hire it out
- Concrete sealer questions homeowners ask
When you need to remove concrete sealer, and when you do not
Stripping is a lot of work, so do it only when a fresh coat over the old one would fail. Strip when:
- The film peels or flakes in sheets.
- A white haze stays after it has had time to dry, as described in fixing white or cloudy stamped concrete sealer.
- The coat has turned yellow, tacky or sticky.
- Years of recoats have built a thick, cracked layer.
- It is the wrong product for the job, such as a glossy film that makes a walkway slippery, and you want to switch types.
- The maker of the new product says to remove the old one first.
Do not strip when the sealer is only worn thin but is sound and clean. A compatible product, applied in a thin coat as the maker directs, is usually enough. Surface damage such as scaling, pitting and spalling is not a sealer problem, and stripping will not fix it. Ontario salt and freeze-thaw cause much of that damage, so look closely at the slab before you decide.
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Step 1: Identify the sealer you have
The type decides the method. Film-forming sealers, such as acrylic, urethane and epoxy, sit on the surface. Penetrating sealers, such as silane and siloxane, soak into the pores.
| Clue | Film-forming | Penetrating |
|---|---|---|
| Look | Sheen, gloss or a wet look | Looks like bare concrete |
| Wear | Peels, flakes, scuffs or chalks | Never peels, just stops repelling water |
| Scrape test | A plastic scraper lifts flakes at a peeling edge | Nothing lifts |
| Stripper patch | Softens or wrinkles in the time on the label | No visible change |
Check old receipts, the pail label or the contractor's paperwork for the product name. If nobody knows, assume a film, and do a stripper test patch in a corner. Thick epoxy and urethane coatings often resist ordinary strippers, which points to grinding.
A penetrating sealer cannot be stripped in the usual sense, since it is inside the concrete. It wears away over time. Ask the maker of any new product whether it will bond to a slab that already holds one.
How to strip concrete sealer: the main methods compared
| Method | Best for | Watch for |
|---|---|---|
| Chemical stripper made for the sealer type | Thin acrylic films, stamped or textured slabs | Fumes, flammability, skin and eye hazards, dwell time, runoff, residue |
| Rinse or pressure wash after the stripper | Lifting softened film and flushing it away | A hard jet etches concrete, so keep the wand moving. See choosing the right PSI for every surface |
| Diamond grinding | Thick, multi-coat, epoxy or urethane films on flat slabs | Silica dust, noise, a changed surface texture and heavy equipment |
| Shot blasting or sanding | Large flat areas | The same dust, and scarred stamped patterns |
| Scraping and brushing | Small loose patches only | Slow work, and a wire brush scratches |
Most homeowners with an acrylic film use the first two. Mechanical removal belongs to the end of the list because it takes equipment, dust control and skill.
How to remove a film-forming sealer with a chemical stripper
- Read the label and safety data sheet. Confirm the stripper suits your sealer, and note temperature limits, dwell time and how to rinse or neutralize.
- Pick the day. A dry, mild, overcast and calm day works best. Strong sun and a hot slab dry the stripper before it works, and wet weather washes it away.
- Protect the surroundings. Cover plants, mask windows, trim and vinyl, keep children and pets away, and block storm drains and downspout outlets.
- Test a small patch in a corner. Check that the film softens in the label time.
- Apply an even coat and keep it wet for the full dwell time. Do not let it dry on the slab.
- Agitate and lift. Work it with a stiff nylon brush, then lift the softened sealer with a scraper and absorbent material. Do not spread the slurry across clean concrete.
- Rinse as the label directs. Repeat on stubborn spots, then give the slab time to dry.
Wear chemical-resistant gloves and eye protection, and a respirator if the label calls for one. Many strippers are flammable and have strong fumes, so keep ignition sources away and ventilate.
Waste needs care. The Region of Waterloo says never to use storm drains to dispose of chemicals, concrete, paint or other hazardous materials. Collect the slurry and take leftover stripper and sealer to a household hazardous waste depot. Check the Region's household hazardous waste page for what the depots and Product Care drop-offs accept.
Grinding, blasting and the dust problem
Concrete, cement and mortar contain crystalline silica. Ontario's guide to silica on construction projects lists grinding, drilling and chipping concrete among the activities that make silica dust, and silica is linked to serious lung disease. Wet methods and tools with dust collection reduce the dust, and respirators are for when those controls are not enough.
That is why mechanical removal is often a job for a contractor with dust extraction and proper protection. If you rent a grinder, ask the rental shop about dust control, use water or a vacuum shroud, and wear a respirator rated for fine dust. Keep neighbours and open windows in mind.
Grinding also takes off a layer of the surface. It changes the texture, and it can scar a stamped pattern or leave a rough finish. Ask for a test patch before the whole slab is done.
Prepare the slab to reseal in Ontario
- Remove every trace of stripper. Residue stops new sealer from bonding. Rinse the way the stripper maker says.
- Let it dry through. Allow days, not hours, after washing, longer in shade or after spring thaw. Tape a clear plastic sheet about 60 cm (24 in) square to the slab for a day. Moisture under it means wait.
- Repair first. Fill cracks and treat scaling, pitting and spalling before sealing. Deep damage needs a repair or a resurfacing opinion.
- Pick a compatible product. Ask the maker whether it suits your slab and the old coating. Many installers choose penetrating sealers for salted driveways because there is no film to peel.
- Choose a dry, mild window. Early fall, or spring once the slab has dried out from the salt season, suits most labels. Avoid dew, rain and a cold slab, and apply thin coats.
- Test a patch of the new sealer before you commit to the whole slab.
To judge when a reseal will be due again, see how long concrete sealer lasts in Ontario. For a slab less than a year old, read when to seal new concrete.
When to hire it out
Call a contractor when the old coating is thick epoxy or urethane, the slab is large or stamped, the sealer is unknown, or the method means grinding and silica dust. Ask any concrete sealing company whether stripping, cleaning, drying time and waste disposal are in the quote, and say what you know about the old sealer. D&D Home Services gives free written quotes for concrete sealing before work begins.
Concrete sealer questions homeowners ask
Can you remove concrete sealer?
Yes, if it is a film-forming sealer such as acrylic, urethane or epoxy. A stripper made for that sealer, or mechanical grinding, takes it off. Penetrating sealers soak into the pores, so they usually cannot be stripped, and they wear away on their own over time.
Does concrete sealer wear off?
Yes. Film sealers thin first in tire tracks and busy strips, then chalk, scuff or peel. Penetrating sealers fade more slowly as salt, abrasion and weather use up the treated layer. A cup of water poured on clean, dry concrete each spring shows how much protection is left.
Does concrete sealer go bad?
Yes, in the pail. Check the label for shelf life, and discard sealer that has skinned over, turned lumpy or will not stir smooth. Many water-based sealers say not to freeze them, so store them indoors over winter.
Can you seal over old concrete sealer?
Sometimes. If the old film is sound, clean and the same type, a thin recoat can bond. If it is peeling, cloudy or unknown, a new coat can trap moisture and fail. Test a small patch, and ask the new sealer's maker what it will bond to.
Key Takeaways
- Identify the sealer first: film-forming sealers can be stripped, while penetrating sealers wear away inside the concrete.
- Strip only when the film peels, stays cloudy or is thick, tacky or the wrong type. Worn but sound sealer can usually be cleaned and recoated.
- Use a stripper made for the sealer, test a patch, protect plants and drains, and never rinse slurry into a storm drain.
- Grinding and blasting make silica dust, so use wet methods or dust extraction, or hire a contractor.
- Reseal only after residue is gone, repairs are done and the slab is fully dry, in mild, dry Ontario weather.
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