What is a grind and seal floor?

A concrete floor that is mechanically ground to remove the weak top layer, open the surface and set the look, and then sealed. There is no resin polishing and no coating build. The concrete stays the floor. The name covers two different finishes. In one, the ground slab is treated with a densifier and a penetrating guard or sealer, which go into the surface and leave no film. In the other, it is sealed with a clear film: an acrylic, a polyurethane or a water based epoxy. Most manufacturers' grind and seal systems mean the film version. Ask which one a quote means, because they wear and age completely differently.

Is grind and seal the same as polished concrete?

No. Polished concrete keeps grinding with finer and finer resin tooling until the concrete itself shines, and the slab is the wear surface. A grind and seal floor stops at the metal grinding. Any sheen comes from the sealer, and on the film version the sealer is what people actually walk on. That is why it costs less to install and more to keep: the film wears and has to be renewed, where a mechanically polished floor is maintained by cleaning and the occasional burnish. The grit sequence guide shows where each finish stops on the same ladder.

Which sealer should I use on a ground concrete floor?

It depends on what the floor has to do. A densifier hardens the surface and cuts dusting but does not repel water or stains, so it is paired with a penetrating guard or sealer. That combination changes the look least and leaves nothing to peel. An acrylic is the cheapest film and the fastest to apply, and it also wears fastest. A polyurethane is the tougher film for abrasion and chemicals, and an aliphatic polyurethane holds its color in daylight. A water based epoxy gives a hard film but can yellow under UV and, on some products, trap moisture in the slab. The product data sheet is the authority on where each one can go and what it can take.

How long does a grind and seal floor last?

The concrete lasts as long as the building. The question is the sealer. A film sealer is the wear surface, so it wears fastest in the traffic lanes, at doorways and where carts turn. It has to be renewed before it wears through, because bare patches take stains and water while the rest of the floor does not, and the floor ends up looking patchy. How often depends on the product and the traffic, and the data sheet or the manufacturer gives the expected cycle. A densified floor with a penetrating guard has no film to wear through. The guard is a maintenance item that is topped up, but the hardened surface underneath stays.

Do I need a moisture test before sealing?

For a film sealer, yes. Moisture moving up through the slab can stop a film from bonding properly, or push it off later as blisters or whitening. Some epoxies are close to impermeable, so they can trap that moisture rather than let it pass. A penetrating sealer or a densifier leaves the surface breathable and is far less sensitive to it. The concrete moisture calculator reads a test result against the bands this site uses; the sealer's data sheet sets the limit for that product and the test method it expects.

Can I coat over a grind and seal floor later?

Usually, but what has to happen first depends on which version it is. A densified floor needs no removal. The densifier is part of the slab, so it is simply ground again, and it grinds slower because it is harder. A film sealer has to come off before a coating goes on, because the new coating would only be as well bonded as the old film. An acrylic in particular is generally recoated only with a compatible acrylic, and a two part resin over it is a removal job first. The guide to removing sealers and curing compounds covers both cases.

Grind and Seal Concrete Floors

Grind the slab, then seal it. The simplest finished concrete floor there is, and the one most often quoted without anyone saying which sealer they mean. That choice decides how it looks, how it wears and what it costs to keep.

Quick answer

Grind the slab with metal bond diamonds to take off the weak top layer and set the look, then seal it. There is no resin polishing and no coating build, so the concrete stays the floor. The name covers two different finishes: a densifier with a penetrating guard, which leaves no film, or a clear film sealer, which becomes the surface people walk on and has to be renewed. Agree which one before anything is quoted.

One name, two floors

“Grind and seal” is used for two finishes that start with the same grinding and then go different ways. They look different on handover day and they age differently for years afterwards, so a quote that just says “grind and seal” has left out the most important line.

Densify and guard

A silicate densifier hardens the ground surface, then a penetrating guard or sealer keeps stains and water out
Nothing sits on top, so there is no film to peel, scuff or wear through
Matte to low sheen, and the concrete looks like concrete
This is what the Grind & Seal preset in the polished concrete cost calculator prices

Clear film sealer

An acrylic, polyurethane or water based epoxy rolled over the ground slab
The film is the wear surface, so it is what people and carts actually wear down
Can add sheen, darken the color and make the concrete easier to mop
This is what most manufacturers’ grind and seal systems mean

Both are legitimate. The mistake is a client expecting one and getting the other: a densified floor that was pictured glossy, or a film floor that was sold as needing no upkeep.

The grind: what it has to do

The grinding is most of the labor in either version, and it has four jobs.

Take off what should not be sealed. Laitance, the weak cement rich skin on top of the slab, plus old sealers, cure and seals, adhesive and contamination. A sealer bonds to whatever is on top, and if that is a weak layer, the weak layer is what fails.
Open the surface. A densifier and a penetrating sealer only work if they can soak in, and a film sealer needs something to key into. The surface profile chart pairs a penetrating sealer or thin film with the finest profile that still keys, because a thin film cannot bury a coarse texture.
Set the look. How deep the metal cuts decides how much aggregate shows, from a cream finish that barely touches the stone to a salt and pepper or fuller exposure. The grit sequence guide explains the four exposure levels, and they apply here exactly as they do to a polished floor. Agree the exposure with the client on a test area, not from a photograph.
Leave a scratch pattern you are happy to seal in. A clear film does not hide the grinding marks under it. If anything, it makes them easier to see. So the grind carries on with finer metal tooling until the scratches are even and consistent across the whole floor, and a densified floor is judged the same way.

Fill cracks, holes and spalls after the grind has opened them up and before anything is sealed. On this floor every repair stays visible, so it is worth deciding with the client whether they want the repairs to blend in or read honestly as repairs.

The hours are a grinding estimate. The grinding production calculator turns passes, machines and rates into time on the floor, and the polished concrete cost calculator loads the densify and guard version as its Grind & Seal finish.

The seal: what each option actually does

These are the same four words the guide to telling whether concrete is sealed uses, and they mean the same things here.

Densifier. Reacts with free lime in the concrete to harden the surface and stop it dusting. It is not a sealer in the everyday sense, because it does not repel water or stains. That is why it is always followed by a guard or a sealer. The grit sequence guide covers when it has to go on.
Penetrating sealer or guard. Goes into the pores and repels water and stains from the inside. It leaves no sheen and no film, and it lets moisture vapor pass. It is topped up as part of maintenance rather than stripped and replaced.
Acrylic. The cheapest and quickest film, and the one that wears fastest. Indoors it is often kept alive with a sacrificial floor finish or wax in the traffic lanes.
Polyurethane. A thicker, tougher film with better abrasion and chemical resistance. An aliphatic polyurethane holds its color in daylight.
Water based epoxy. A hard film, but epoxy can yellow under UV, and some products are close to impermeable, which can trap moisture coming up through the slab.

Film sealers are often built as a system rather than one product, for example an epoxy primer under a polyurethane topcoat. The data sheet for each layer says what it can go over and what can go over it.

Before a film goes down: moisture, grip and daylight

Test for moisture. Moisture moving up through the slab can stop a film from bonding, or push it off later as blisters or white haze. A penetrating treatment is far less sensitive to it. The concrete moisture calculator reads a test result, and the sealer’s data sheet decides whether that result is inside its limit.
Decide on grip. A clear film smooths the surface, and a glossy wet look sealer can be slippery when wet. Most sealer makers sell a traction additive mixed into the final coat. As with any resin floor, slip resistance has to be specified rather than assumed.
Check the light. Near windows, glazed doors and roller doors, an epoxy film can yellow. The yellowing guide explains why. An aliphatic polyurethane is the usual answer where daylight reaches the floor.

Upkeep is part of the specification

A film floor is cheap to install because the sealer does work that polishing would otherwise do, and the sealer wears. It goes first in the traffic lanes, at doorways and where carts and pallet trucks turn. Renew it before it wears through: once bare concrete shows in patches, those patches take stains and water while the rest of the floor does not, and the floor looks worn long before it is.

Renewing has rules of its own. An acrylic is generally recoated with a compatible acrylic, and a different film on top of it, particularly a two part resin, is a removal or preparation job first, set by the new product’s data sheet. The guide to removing sealers covers taking a film off.

A densified floor with a penetrating guard has nothing to wear through. The guard is topped up and the floor is cleaned with a neutral cleaner. If the client later wants a coating, the densifier needs no removal: it is part of the slab, and the floor is simply ground again, a little slower because it is harder.

Put the upkeep in the quote. A client comparing a grind and seal price against a polished floor or a coating is comparing installation costs, and the film version’s real cost includes every recoat.

Where grind and seal fits

Sound slabs where the client wants the concrete to show: offices, retail, showrooms, breweries, restrooms and light warehouse areas.
Budgets that cannot stretch to a polish or a coating, with the upkeep explained up front.
Dusting slabs, where a densifier and guard fix the actual complaint without changing the look much.
Floors that must stay breathable, where the penetrating version avoids putting a film over a slab that moves moisture.

Where it is the wrong choice

Slabs that are badly damaged, stained or patched. Grinding and sealing reveals the concrete, flaws and all. If the client will not accept what the slab looks like, it is a coating floor, and polished concrete vs epoxy walks through that decision.
Heavy wheeled traffic on a film. Forklifts and steel wheels wear a thin sealer quickly. A densified floor or a polish keeps the concrete as the wear surface.
A client who wants gloss and no recoats. That is a polished floor. On a grind and seal floor the gloss comes from a film, and films are renewed.
Hot water, steam and harsh chemicals. A thin sealer is not a chemical or thermal shock system. The urethane cement system is built for that exposure.

What this page does not cover

Figures. Grit numbers, coverage, recoat intervals and moisture limits vary by machine, slab and product. This site does not pin them for this finish, so it does not print them. The data sheets and the calculators above are the place for each one.
Polishing. Carrying on past the metal grinding into resin tooling is a polished floor, and the grit sequence guide covers it.
Coatings. A primer and build coats with a finished thickness is a coating system, not a seal. The rest of this systems library covers those.