How to clean stucco?

How to clean stuccoExterior stucco is a very durable attractive finish but has to be cleaned periodically to keep it looking great.

Stucco is porous and textured which allows water, dirt, mildew, and pollen to settle in the stucco and become a breeding ground for mold and mildew. If you see black stains or green stains on your stucco it’s a sure sign it’s time to call the professionals to get it cleaned.

When cleaning stucco there are certain factors to consider. The first is what has to be removed from the stucco. Is it green mold and mildew or is it rust or asphalt stains or a combination of all of these.

Once the source and type of stain has been determined the cleaning method is selected.

High-pressure water is not a safe method for cleaning stucco and can easily and permanently damage the finish.

Soft washing, which is the use of low pressure and strong detergents, is another option but has its drawbacks. The strength of the solution could kill plants, damage painted surfaces or etch glass.

Hot water low-pressure detergent washing is the preferred method for cleaning stucco. The solutions can be made 50% weaker than that used in softwashing because the heat of the water will accelerate the detergents allowing for a faster clean time and still achieve a 100% kill ratio of green mold and mildew.

BASF Synergy is the most widely used stucco finished today and they recommend cleaning their products with diluted solutions, low pressure( under 400psi) and water temperature at the gun under 140 degrees Fahrenheit.

Removing rust and asphalt stains from stucco is possible but rarely ever 100%. The rust usually is being caused by well water in lawn sprinklers getting on the siding. This can be removed by using a special acid just for rust removal and is not part of a normal cleaning quote. Check with your contractor to see if they have the right product and what the additional cost would be for rust removal.

Asphalt is usually coming from run off of the roof shingles either bypassing a gutter or over a gable end then dripping on the finish. This is a really tough stain to get out and at best you can hope for a 50% removal. There are special solutions for asphalt and tar removal but they rarely work 100%.

Stucco should be clean on a two-year cycle to remove green mold. Green mold absorbs water and will keep stucco wet almost year-round thereby causing the stucco to spall and crack if left unchecked.  A great appearance is an added benefit.

If you’d like a free consultation with one of our friendly Customer Care Specialists please feel free to contact us at 732-775-1242.