Sealers and coatings
What is the difference between a concrete sealer and a coating?
A sealer soaks into the concrete and leaves it looking like concrete, while a coating builds a film on top and changes the color and the surface.
The short version
- A penetrating sealer goes into the concrete. A coating goes on top of it.
- A sealed floor still looks like concrete. A coated floor looks like a finished floor.
- Sealers are the usual answer on a driveway, a sidewalk and exposed exterior concrete.
- Coatings are the usual answer on a garage, a basement or a shop floor.
- People often say sealing when they are picturing a coating, so it pays to say which you mean.
What a sealer does
A penetrating sealer is a thin liquid that soaks down into the top of the concrete and sits in the pores. It does not build a layer you can see or feel. When it is dry the floor looks like concrete, because it is concrete, with the pores partly filled in. Film-forming sealers leave a thin glossy layer instead, and they turn up on stamped and decorative work.
What a sealer buys is resistance to what soaks in. Water carrying road salt gets into bare concrete, and in this climate it freezes in there and pushes the surface apart, which is what scaling and spalling are. A sealer slows that down, and it gives oil and stains less to sink into.
What a coating does
A coating builds. It goes onto prepared concrete as a resin, in layers, and ends up as its own material bonded to the slab with real thickness to it. The floor is a different color, a different surface and a different thing to clean, and the concrete underneath is not what you are walking on any more.
That thickness is what takes the abuse. A wear layer takes the tire heat, the shovel edge, the dropped tools and the salt instead of the concrete taking them. It also means the floor can be finished: flake, a solid color, a texture picked for the room.
A coating asks more of the prep to earn it. The slab gets ground, the moisture gets checked, cracks and spalled edges get dealt with, and the floor has to be empty while the work happens. A sealer is a far smaller job.
How to tell which one you want
Start with the room. Exterior flatwork, a driveway, a sidewalk, a stamped patio, is usually sealer country, because nobody is asking it to look like a finished floor. Sealer is also the answer where the concrete itself is the look you are after.
Then ask what you want to see when you open the door. If the answer is a floor that looks finished, a color, a flake, something that cleans like a countertop, that is a coating and no sealer gets there. If the answer is that the concrete should look like concrete and take less damage doing it, that is a sealer.
The word people use is not much of a guide. Plenty of people call and ask about sealing a garage floor while picturing a flake floor. Describe the finish you want and whoever is quoting it can tell you which product that is.