Imprinted Concrete Driveways: Cleaning and Re-Sealing

Pattern imprinted concrete is the surface where cleaning and sealing are not two separate decisions. If you do the first without the second, you have made the drive worse.

I clean imprinted concrete. I do not re-seal it, so on this surface I am half the job and you need to line up the other half before you book me. If nobody is going to re-seal it, leave the drive alone for now, and read on for why.

Here is why.

How the surface is built

Imprinted concrete is poured as a single slab. While it is still workable, colour is applied to the top: a base colour through the mix or broadcast onto the surface, then a release agent in a contrasting shade, then textured mats are pressed in to give the stone or brick pattern.

Then, crucially, the whole thing is sealed with an acrylic coating.

That coating does three jobs. It locks the surface colour layer down. It gives the drive its characteristic slight sheen. And it protects the concrete from water, salt and oil.

The colour lives in a thin layer at the very top, and it is the sealer that keeps it there.

What actually goes wrong

The sealer degrades. UV breaks the acrylic down, tyres abrade it, and freeze-thaw works at it. Typical life is five to eight years, less on a drive that gets full sun or heavy turning.

As it goes, you get the familiar sequence. The sheen dulls. The colour looks washed out and patchy. Algae starts to grow, because the surface is now open. In the tyre tracks, where wear is heaviest, the colour begins to lift.

At that point the drive looks dirty, so people have it cleaned.

Why cleaning alone makes it worse

A pressure wash on a drive with a degraded sealer removes what is left of the sealer along with the dirt.

The drive comes up looking better, because you have removed the patchy failing coating and the growth on top of it. Underneath is the bare colour layer, unprotected, on a porous concrete slab.

From there it deteriorates quickly. Water gets into the concrete. Frost works on it. The colour layer, which was never meant to be the wearing surface, abrades under tyres. Within a couple of years you have visible grey concrete in the tracks and there is no way back short of a full resurface.

That is why I quote imprinted concrete as clean and re-seal together, or I do not quote it. Taking money to clean one and leave it bare would be selling somebody a problem.

Doing it properly

Clean at reduced pressure. Never a turbo nozzle. A surface cleaner at moderate pressure with a wide fan. The aim is to remove the failed sealer and the growth without cutting into the colour layer.

Remove the old sealer properly if it is heavily built up. Successive re-seals without cleaning between them can leave a thick, yellowed, flaking film. That needs a chemical stripper rather than pressure, and it is a bigger job.

Let it dry completely. Concrete holds water and this matters more here than almost anywhere. Sealing over trapped moisture gives a milky white blush under the film that can only be fixed by stripping it back off. Give it several dry days.

Re-sand the joints if the pattern has open joints. Some imprinted work has genuine joints; most does not.

Apply the sealer in two thin coats rather than one thick one. Thick acrylic goes cloudy and stays tacky. Two thin coats give a better finish and last longer.

Add grit to the final coat if the drive is on a slope. Sealed imprinted concrete is slippery when wet, which is its main practical drawback, and an anti-slip additive in the top coat deals with it.

What it costs

Cleaning is £4.50 a square metre at my rates.

Re-sealing is the significant part, and on imprinted concrete it takes considerably more material than an impregnating sealer on stone, because you are building a film rather than lining pores.

Budget for the two together rather than being surprised by the second number. On a 40 square metre drive you should expect the sealing to cost more than the cleaning did.

How often

Re-seal every four to six years, and clean lightly in between.

A drive that is re-sealed on schedule never gets to the state where a heavy clean is needed, which is the cheapest way to own one of these. A drive that is left for twelve years needs stripping, which is expensive.

If it is already too far gone

Where the colour layer has worn through to grey concrete in the tyre tracks, sealing will not bring it back. Sealer is clear.

The options at that point are a re-colouring system, which is a specialist coating applied over the whole drive, or resurfacing. Neither is a cleaning job, and I would tell you that rather than take a booking.

Honestly, imprinted concrete is a surface that rewards maintenance and punishes neglect more than any other driveway material. If you have one, the useful thing to know is the date it was last sealed.

How to tell what state your sealer is in

Throw a cup of water on it. On a sealed drive the water beads and sits. On a drive where the sealer has gone, it darkens the concrete immediately and soaks in. Try it in the tyre tracks and again at the edge where there is no traffic; the difference between the two tells you how far along you are.

Look for sheen. Sealed imprinted concrete has a slight gloss. A completely matt surface means the sealer has gone.

Check for flaking. White or yellowish flakes lifting off, particularly in sheltered areas, mean an old acrylic film breaking down. That needs stripping rather than over-coating.

Look at the tyre tracks. If the colour there is noticeably paler than at the edges, the colour layer itself is wearing. That is the point at which sealing alone will not fix the appearance.

Cloudiness under the sealer

The most common complaint about imprinted concrete after somebody has re-sealed it, and it has three separate causes worth distinguishing.

Moisture trapped underneath. Milky white, appears within days, worst in the areas that dry slowest. Caused by sealing before the slab was dry through. Requires stripping.

Sealer applied too thick. A general haze with a slightly plastic look. Sometimes recoverable with a solvent wipe, often not.

Old sealer degrading under new. Patchy, follows the pattern of the previous coats. Needed stripping before the new coat went on.

All three are avoidable and all three are why I will not re-seal a drive that has not been properly dried, however keen somebody is to have it done that week.

The anti-slip question

Sealed imprinted concrete is slippery when wet. It is the main practical criticism of the surface and it is a fair one.

The solution is a fine aggregate additive, usually aluminium oxide or a polymer grit, stirred into the final coat. It is nearly invisible and it makes a substantial difference.

On a sloping drive, or one with steps, I would treat it as standard rather than optional. Ask for it; some contractors do not offer it unless prompted.

Costs over the life of the drive

Imprinted concrete is often sold on the basis that it is low maintenance. It is not, particularly, and it is worth knowing the real cycle before you buy one.

Every four to six years: clean and re-seal. On a 40 square metre drive, budget several hundred pounds each time.

Every fifteen to twenty years, roughly: a strip and re-seal, which costs more because removing built-up old acrylic is slow work.

At some point: re-colouring or resurfacing, once the colour layer has worn through in the tracks.

Compared with block paving, which needs cleaning and re-sanding and can have individual damaged blocks swapped, imprinted concrete is less forgiving. It looks excellent when maintained and there is no cheap way to rescue one that has been neglected for fifteen years.

That is not a reason to avoid it. It is a reason to know the date it was last sealed and to put the next one in the diary.

Booking it, given that I do not seal

Find your sealer first and ask when they can come. Then book the clean two or three dry days ahead of that, so the slab has time to dry all the way through. That order matters more on imprinted concrete than on anything else, because the window between a stripped surface and a fresh coat is the window where the colour layer is exposed.

Three things worth asking the sealer. Which acrylic, and how many coats. Whether the price includes an anti-slip additive in the top coat, because on a sloping drive it should. And whether the old coating needs stripping first or can be re-coated over, which depends on how far gone it is and is the single biggest swing in the price.

If they want to seal the same day as the clean, get somebody else.