Resealing stamped concrete

Resealing means applying a new coat of sealer to stamped concrete whose previous sealer has worn away but whose surface is still sound. It is the maintenance that separates a floor that lasts for decades from one that needs a full restoration after ten years. These are the decisions involved in resealing stamped concrete: which sealer, which sheen, how many coats, when, and how long to let it dry.

Types of sealer for stamped concrete

There are three families of sealer for stamped concrete, and each has its place.

• Solvent-based acrylic. The most used outdoors. It penetrates the pores, brings the colour to life and gives the wet-look that most people associate with stamped concrete. It recoats well over itself, because the solvent softens the previous coat and fuses with it. It smells during application and needs a completely dry floor.
• Water-based acrylic. No smell and fewer restrictions on application, but it enhances the colour less and usually gives a more matt finish. It is the option when houses are very close together, on enclosed terraces, or when the floor has some residual moisture that will not quite go. It is not always compatible with an earlier solvent-based acrylic; that has to be checked.
• Aliphatic polyurethane. Harder and more resistant to UV radiation, chlorine and hot car tyres. It is used on very exposed pool areas and on busy driveways. It needs a very well prepared surface and, over an old acrylic, a primer or stripping first.

The choice depends on the sealer already on the floor, the exposure and what you expect to see. The guide to water or solvent-based sealer compares them point by point.

Gloss, satin or matt

The level of sheen comes from the sealer and its solids content. Gloss enhances the colour but shows imperfections and dust more; satin is the most common middle ground; matt is discreet and hides wear. In Mallorca, where the red dust of the calima and limestone dust settle on everything, satin usually ages better than high gloss.

Anti-slip additive

A freshly applied sealer, especially a gloss one, is slippery when wet. That is why on pool surrounds, outdoor showers, steps and ramps we add an anti-slip additive to the last coat: polymer microspheres or a very fine aggregate that stays suspended in the film and gives grip without changing the look. You feel it with bare feet and you do not see it.

Preparation

Eighty per cent of a good reseal is preparation. First we identify which sealer the floor has with a solvent test in a corner. Then controlled pressure washing removes dirt, green algae, chlorine residue and any film that is loose. Where the old sealer is flaking, it is stripped completely; a new coat over a layer that is coming away will come away with it. Cracks and broken edges are repaired first, not afterwards. And the floor is left to dry: not just the surface but the pores too, because moisture trapped under the sealer is what causes white patches.

How many coats, and how

Two thin coats, applied crosswise. The first by short pile roller or sprayer, spread out until there is no pooling; the second 4 to 8 hours later depending on the temperature, at right angles to the first. A single thick coat is the most common mistake: it is slow to dry, traps solvent and turns white or peels within months. Two thin coats form a continuous, flexible and even film.

Drying and traffic

• Touch dry: 1 to 4 hours depending on the sealer and the temperature.
• Foot traffic: 24 hours after the last coat.
• Furniture and planters: 48 hours, with felt pads underneath.
• Vehicles: 48 to 72 hours. Hot tyres on a sealer that is still curing leave marks.
• Full hardness: 7 to 10 days.

In low temperatures or high humidity, all of these times get longer.

When stamped concrete can be sealed in Mallorca

The sealer needs a dry surface, a temperature between 10 and 30 degrees and no risk of rain in the following 24 hours. That rules out the middle of the day in July and August, when the floor goes above 40 degrees and the solvent evaporates before the sealer has penetrated, leaving bubbles and roller marks. In summer we work early in the morning or towards evening. In autumn we watch for storms and do not seal the day before one. The best windows are usually April to June and September to November, always with the forecast in front of us.

What resealing recovers and what it does not

A reseal brings back the depth of the colour, the sheen you choose, water repellency and protection against sun, salt air and stains from oil or pine needles. What it does not do is fill cracks, replace colour where the pigment has gone completely or disguise a chipped patch: that is repair and colour restoration work, both part of a full restoration. If your floor has only lost its sheen and water no longer beads on it, resealing is enough. If it is also white, cracked or peeling, it needs the earlier steps first.