How to Prepare Concrete for Staining

Concrete staining can bring new life to old concrete floors. Although the stains are effective they do need proper preparation of the floor before application.

Step 1 – Look for Problems

Examine the area to be stained and identify any problem areas for cleaning.

Step 2 – Basic Clean

Use a cleaner that does not leave a residue and a stiff scrubbing brush to clean away surface dirt, grease, and adhesive residue. Do not use a wire brush because that is too harsh. Oil and grease spots might need a direct application of cleaner and several attempts before they are cleaned away. Make sure the area is well washed with clean water after such treatment. Paint spots and spills can be removed by scraping or repeated application of paint thinners. Some really stubborn stains might need the use of a high-pressure washer to remove them.

Step 3 – Surface Irregularities

If you are trying to create a perfect surface you will need to fill any cracks and depressions in the concrete flooring. There are concrete and acrylic mixes that can be used to fill irregularities. Ensure that they will not shrink when drying and that they will accept a concrete stain. If you would rather use concrete as the filler make sure that you use a bonding agent to make sure the new concrete sticks.

Step 4 – Surface Features

Sometimes the cracks and depressions in concrete can add to the character and it might be desirable to leave them as features.

Step 5 – Grind the Floor

If the floor still looks stained or patchy hire a floor grinder to grind away a thin layer from the surface of the concrete. Use a medium grade grinding head and apply it to the whole floor surface to ensure an even finish. This will remove the most stubborn remnants of most penetrating stains like oil and grease. All of the surface stains will be ground away.

Step 6 – Acid Wash

If grinding the floor is not possible to use a mix of 4 parts water to 1 part muriatic acid and sprinkle it onto the concrete (a watering can with a rose is ideal for this). Muriatic acid gives off strong fumes and you should wear a respirator when mixing or handling it. Wear rubber boots and gloves. The mixture will foam when applied. Leave it to work on the concrete for about half an hour then wash it off with plenty of water and a long-handled brush.

Step 7 – Leave the Floor to Dry

Give the floor at least 48 hours to dry thoroughly then sweep off or vacuum any concrete dust that still remains. The floor should now be as clean as you can make it and is ready for the stain to be applied. The stain can be applied with a paintbrush or roller. If you can mask areas that should not be stained, you can also use a low-pressure sprayer.

A newly stained concrete floor will add life and vitality to a building. It is well worth the effort involved.