My stamped patio turned white and slick. Is that the sealer or the concrete?

Is the problem in the sealer or in the concrete?

Most of the time it is the sealer. Every stamped patio has two layers, a colored four-inch slab and a thin sealer film laid over it. The film is what goes white, slick or flaky. The slab under it usually has years left, and a crew that does stamped concrete in Henderson can strip and redo the film without touching the pour.

You can sort most patios from the back step. Pour a glass of water on a spot that looks dull. Where the film is worn through, the concrete drinks it and goes dark at once. Where the film is still there, the water sits on top. A white patch or a loose edge that scrapes up under a fingernail is film. Concrete does not come up under a fingernail. Where the slab itself is going, the top is rough and sandy and the pattern has worn away, and that is the other kind of problem, at the bottom of this page.

The sections below take the usual complaints one at a time and say which layer each one lives in. If the stamped work in question is the driveway, tires and winter salt add their own wear, covered in stamped concrete on a driveway.

Why did my stamped patio turn milky white in patches?

That cloudiness is called blush, and it is water caught in or under the sealer. It happens when a solvent-type sealer gets rolled on late on a humid evening, over a slab that never fully dried, or when a thick film holds water under it after rain. The concrete is fine. A crew can usually clear it by reworking the film so the trapped moisture escapes, or by stripping and recoating that area.

The Ohio Valley makes blush common. A July evening here turns damp fast, and a patio that was dry at six can be wet with dew by ten, before a sealer rolled on late in the day has set. On the river side of town, where the water table sits high in a wet spring, a slab can hold moisture from below as well.

Shade does it too. Under the sycamores and oaks on the older streets near downtown a patio can stay damp underneath for days after a rain, and sealer put down over that dampness traps it. The white usually shows in the shadiest corner first, or along the edge nearest the lawn sprinkler, while the sunny middle of the patio stays clear.

It is not a reason to replace anything. Blush that comes back every summer in the same spot does say the film there has gotten too thick to breathe, and the next reseal should take that patch down rather than add to it.

Why is a stamped patio so slick when it rains?

Gloss builds up. Each reseal lays a new coat over the last one, and after several rounds the pattern fills in and the surface turns smooth and shiny, close to a finished floor. Wet, it gets slippery. The usual fix is fewer coats and a fine grit broadcast into the last one, which gives shoes something to grip without dulling the color much.

The spots that go slick first are the ones that stay wet. Under the downspout. The landing outside the back door, where a wet dog or a dripping swimsuit comes in. The edge around a pool or a hot tub, which is wet half the summer, and what a hot tub needs from a patio covers the slab side of that. Some slip comes with any sealed surface, one of the trade-offs listed on the stamped concrete page.

Why is the sealer peeling off in sheets?

Two things cause it. Too many coats stacked up over the years until the bottom one lets go, or a different type of sealer rolled over the original, which never really bonds to it. Either way the film comes off in clear or tinted sheets, and the concrete under it is usually still sound, its color intact.

Patching a peeling film does not hold. A new coat over a loose one peels with it, so the fix is to strip the patio back to bare concrete, clean it, and start the sealer over with one type in thin coats. An ordinary reseal on a stamped patio runs $350 - $700. A strip-and-reseal runs above that, since the old film has to come off before the new one goes on, and the crew prices it on the site visit after seeing how much of the old film is loose. The work wants a dry stretch in spring or fall.

Can the color come back on a faded stamped patio?

Most of it, often. The look of a stamped patio comes from three places: the integral color mixed into the concrete, the release color dusted on before stamping, and the sealer, which wets everything out and makes it read deeper. When a patio goes pale, the sealer has usually worn thin and the release color has weathered out of the high spots. A fresh film, or a tinted one, brings much of that back.

What a reseal cannot do is make the slab darker than it was poured. The integral color is in the concrete itself and fades very little, so on a worn patio it is the floor the color comes back to. A tinted reseal can push the release color back toward where it started, and a crew will usually test a corner first so you can see it dry. A patio facing west fades fastest, which is why the sealer schedule a stamped patio here needs runs by exposure.

When is it the concrete, and not the sealer?

When the damage goes into the slab. Freeze and thaw is hard on concrete in Henderson, and once the film wears through, water gets into the top of the slab and the winters go to work on it. Three things point at the concrete itself:

• The surface flaking off under the film, leaving a rough, sandy patch where the pattern used to be. That is scaling, and it is worst where ice melt went down by the door or on the steps.
• A crack running across the pattern, through the stones instead of along a grout line. The way to read it is in why concrete cracks here.
• A section that dropped, tilted toward the house or sits lower than the panel beside it. That is the ground under the slab, covered in why a slab sinks and what lifting fixes.

Light scaling on a few spots can sometimes be patched and sealed. A broken or sunken section usually has to come out and be poured again, and new stamped work runs $16 - $24 per sq ft. One limit is worth knowing up front. A re-poured section will not match the old pattern and color exactly. The mats may be the same, but the old concrete has years of sun on it, and the new panel will read a little different for a long time. Crews generally hide that by ending the new pour at a joint or a border, so the change in color falls on a line the eye already expects.