STUCCO CLEANING

EIFS vs. Traditional Stucco: The Difference Matters

Traditional three-coat stucco is a hard, dense finish applied over metal lath or masonry. EIFS — Exterior Insulation Finishing System, sometimes called Dryvit — looks nearly identical from the street but is structurally very different. The finish coat sits over a foam board substrate rather than a rigid wall, and that foam board has no ability to drain water that gets behind it.

The cleaning approach for EIFS is more conservative by necessity. Even 500 PSI directed at a joint, seam, or any area where the finish has a hairline crack can force water behind the foam board and into the wall cavity. We clean EIFS at 200–300 PSI maximum, relying on chemistry dwell time rather than pressure to lift biological growth. The results are the same; the surface survives intact.

If you are unsure which system your home has, the easiest field test is a gentle knock on the wall surface. Traditional stucco sounds solid. EIFS sounds slightly hollow because of the foam layer beneath.

The Northeast Florida Failure Mode: Efflorescence

Northeast Florida’s humidity and salt air create a specific failure pattern on stucco that is frequently misdiagnosed as exterior grime. Efflorescence — the white or light-grey crystalline deposits that push through the surface — is not dirt. It is mineral salt carried by moisture migrating outward through the wall cavity, deposited as the moisture evaporates at the face of the stucco.

Cleaning removes the surface deposit effectively, and the wall looks correct immediately after the job. But if the moisture source inside the wall cavity is not identified and corrected — a failing pan flashing, a cracked window sill, improperly sealed penetrations — the efflorescence returns within a few months as new mineral deposits push through. We document efflorescence locations when we find them and note whether the pattern is consistent with a point source or diffuse wall moisture.

Active efflorescence is also a signal that the stucco’s protective coating has been compromised in that zone. Sealing over it without addressing the moisture source traps the salts and accelerates the delamination of any coating applied afterward.

What Goes Wrong: Chemistry Damage on Stucco

Stucco is alkaline by nature, and acid-based cleaners react with that alkalinity by etching the surface. The etching is not always immediately visible — it shows up as a matte, dusty texture change and color shift in the affected zone, typically weeks after the job when the homeowner notices that one wall looks different from the others.

Bleach concentration is the other common damage vector. Pigmented stucco — integral color that runs through the finish coat — will bleach permanently at sodium hypochlorite concentrations above approximately 3%. The lightest-colored stucco finishes are the most forgiving; mid-tone tans, greys, and earth tones are the most vulnerable. We adjust SH concentration per surface, per elevation, per level of biological load. There is no one-size number.

Cleaning Before Painting: Why the Order Matters

Many homeowners schedule a paint job to cover algae streaking and biological buildup on stucco because it appears to solve the problem quickly. Painting over contaminated stucco produces a paint job with a shortened lifespan — the biological growth under the paint continues to metabolize and break down the paint bond from beneath, and the new paint begins to peel within one to three years.

The correct sequence is clean first, allow the surface to dry and cure fully (typically 48–72 hours in NE Florida humidity), then prime and paint. The painter gets a clean, properly bonded surface. The paint job lasts significantly longer. The economics of doing it in the right order are clear: a thorough cleaning before a repaint protects a $4,000–$12,000 paint investment for the full life of the coating.