Two different wall systems are sold across metro Atlanta under the single word stucco, and one of them is foam board. Traditional stucco is portland cement plaster over lath. EIFS, the synthetic system, is rigid insulation board with a thin reinforced coating on the face of it. A cleaner who cannot tell the two apart is guessing at a pressure ceiling on a wall where guessing wrong drives water into insulation, and the damage does not show up on the day of the wash.
The guide below separates the two systems, gives the published cleaning limit for each, names the document every limit comes from, and gives the date that document was read. Where no source publishes a number, this page says so rather than inventing one. Rare Earth Ltd quotes exterior cleaning per property after a walk, so no price for our own work appears anywhere on this page. The operational detail lives on the soft washing and house washing service pages.
What is the difference between traditional stucco and EIFS, and why does it decide the whole job?
Traditional stucco is a cement product with mass behind it, and EIFS is a coating over foam, so the two systems answer to completely different failure modes. ASTM International publishes the governing specification for the cement version: the scope of ASTM C926 states that the specification "covers the minimum technical requirements for the application of full thickness portland cement-based plaster for exterior (stucco) and interior work" (ASTM International, scope of ASTM C926, read 2026-09-03). The companion standard covers what the plaster is applied to. ASTM C1063 covers "the minimum technical requirements for the installation of lathing and furring for the application of exterior and interior portland cement-based plaster, as in Specification C926" (ASTM International, scope of ASTM C1063-25, read 2026-09-03).
EIFS is defined by its own trade association. According to the EIFS Industry Members Association, citing the International Building and Residential Codes and ASTM International, "EIFS are a non-load-bearing exterior wall cladding system that consists of an insulation board attached adhesively or mechanically, or both, to the substrate; an integrally reinforced base coat; and a textured protective finish coat" (EIFS Industry Members Association, About EIFS, read 2026-09-03). The association also describes the current generation, EIFS with Drainage, as carrying an air and water-resistive barrier plus "a method to collect and redirect incidental moisture that bypasses the outermost surface", and calls those systems "the predominant EIFS system in use today".
The practical consequence sits in that definition. On EIFS, everything that keeps water out of the wall is in a thin reinforced coating, and the layer underneath is insulation that has no way to dry once it is wet. On three-coat stucco the water control sits somewhere else entirely, and the Stucco Manufacturers Association states where: "The weather resistive barrier is located beneath the cement coating." The association names that barrier as the component protecting the home from moisture intrusion (Stucco Manufacturers Association, Three-Coat Stucco Maintenance Guidelines, read 2026-09-03).
How do you tell EIFS from three-coat stucco on a wall you did not build?
Four checks separate the two systems from the ground, and none of them requires a ladder or a moisture meter.
- Tap the wall. Portland cement plaster over lath sounds dense and feels cold. EIFS returns a hollow knock, because the knock is landing on foam board.
- Look for the weep screed at the base. The Stucco Manufacturers Association describes the drainage path on a three-coat wall in one sentence: "Any moisture that penetrates the weather-resistant barrier drains out at the weep screed." A continuous metal drip edge low on the wall is a three-coat signature.
- Count the joints. Sealant joints are a designed component of an EIFS wall rather than an afterthought. EIMA Technical Bulletin 003, July 2024, notes that "a 3/4-inch joint width is often used in the EIFS industry" and lists floor lines of multi-level wood-frame construction, building expansion joints, dissimilar substrates, and abutments to windows or doors among the "locations that typically require placement of a sealant joint".
- Look at a window return or a corner bead. A rasped foam edge reads soft and slightly rounded. A cement corner over metal bead reads square and hard.
When the four checks disagree, treat the wall as EIFS and clean to the lower limit. Cleaning three-coat stucco at EIFS pressure costs an extra rinse pass. Cleaning EIFS at cement-plaster pressure costs a lamina.
What water pressure is safe on EIFS and on acrylic-finished stucco?
Two manufacturers publish the same ceiling, and both of them state it as a hard limit rather than a recommendation. According to Sika Corporation's LaHabra technical bulletin, revised March 2024, a cleaner should "Never use water pressure more than 500 psi or allow pressure nozzles to come within 2 feet of the wall", because "Excessive pressure may damage textured finishes and EIFS lamina." The same bulletin sets the tip: "Use fan type tips (30-45 degrees or greater) on the pressure washer."
Sto Corp., which is headquartered in Atlanta, publishes the same number for acrylic and acrylic elastomeric finishes on stucco. According to Sto Corp.'s Stucco Repair and Maintenance guide No. 1.01, "If a pressure washer is used, keep the pressure at approximately 200 to 500 psi and keep the nozzle several feet from the surface. Do not exceed 500 psi pressure, as the surface integrity of the finish can be destroyed with higher pressure washing." Sto lists high pressure washing in excess of 500 psi, sandblasting, steam cleaning, solvent-based cleaners and wire brushes under a heading titled Do Not.
| Surface | Published limit | Who published it |
|---|---|---|
| EIFS and acrylic stucco finish | Not more than 500 psi, nozzle no closer than 2 feet, fan tip 30 to 45 degrees or wider | Sika Corporation, LaHabra technical bulletin, rev. March 2024 |
| Acrylic and acrylic elastomeric finish on stucco | Approximately 200 to 500 psi, nozzle several feet off the wall, never above 500 psi | Sto Corp., Stucco Repair and Maintenance No. 1.01 |
| Bare three-coat portland cement plaster | No psi figure published. The method given is a garden hose stream plus brushing | Stucco Manufacturers Association, Three-Coat Stucco Maintenance Guidelines |
The third row of that table is the honest finding, and it is the one most stucco cleaning articles get wrong. No document read for this page publishes a pressure ceiling for bare cement plaster, so a confident figure such as 1,500 psi for hard-coat stucco, which circulates widely on trade sites, traces to none of the sources listed below. The Brick Industry Association's 400 psi figure is stated for brick and does not reach stucco or EIFS, and James Hardie's fiber cement figures do not either. Carrying a number across claddings is how a wall gets damaged with a citation attached to it.
What does the Stucco Manufacturers Association say about washing three-coat stucco?
The association's published homeowner method uses a garden hose, not a pressure washer, and runs in four steps. The Stucco Manufacturers Association's Three-Coat Stucco Maintenance Guidelines set them out in this order.
- "Pre-wet the wall, saturating it. Start at the bottom and work to the top."
- "Use a garden hose to direct a pressure stream of water against the wall to loosen the dirt. Start at the top and wash the dirt down the wall. Caked-on dirt may require brushing."
- "Mild cleaners may be used to remove stains. Choose water-soluble cleaners that will not attack Portland cement, lime, or oxide pigment colors."
- "Flush remaining dirt off the wall with a follow-up rinse."
Two details in that sequence carry more weight than the tool does. Pre-wetting from the bottom up saturates the lower wall first, so dirty water running down from above has nowhere dry to soak into and cannot leave a streak. Sika states the same principle for EIFS: "It is recommended to keep lower elevations wet to prevent run-off from above from causing streaking." The chemistry constraint is the second detail, and the association names the three things a cleaner has to protect: portland cement, lime, and the oxide pigments that color an integral-color finish. An acid cleaner sold for masonry will strip pigment out of a colored stucco finish and leave a pale patch that no rinse recovers.
Why does stucco grow algae faster in Georgia than in a dry climate?
Georgia supplies the two inputs biological growth needs, water and warmth, on a schedule that never fully switches off. According to NOAA's National Centers for Environmental Information, the 1991-2020 climate normal for annual precipitation at Atlanta Hartsfield-Jackson, station USW00013874, is 50.43 inches, and the annual mean temperature normal at the same station is 63.6 degrees F (read 2026-09-03). The seasonal split is the part that matters for a wall. NOAA's June through August precipitation normal for that station is 13.59 inches, so more than a quarter of the year's rain lands in the three months when the wall is warmest.
Stucco texture then holds that water. Every dash, lace and knockdown finish is a field of small pockets, and each pocket keeps a film of moisture long after a flat surface has dried. North elevations and walls under deep eaves dry slowest and colonize first, which is why an owner watching one side of a building go green while the others stay clean is watching drying time, not dirt.
One published warning is written for exactly this climate. Sika's LaHabra bulletin states: "Trisodium phosphate detergent is a food source for mold. Do not use trisodium phosphate detergent without bleach in hot humid climates. Mold must be removed with bleach, or it will return." A TSP-only wash in Georgia therefore does worse than nothing: the wall looks clean for a season and the detergent residue feeds the return. The same document gives the working ratio for the biocide step, "a solution of 1 part bleach and 20 parts water", applied to kill mold or mildew.
What does soft washing do that pressure washing does not?
Soft washing kills the organism instead of knocking the color off it, and every source in this set says the water is not the active ingredient. Sika's LaHabra bulletin puts it in one sentence: "The chemicals provide the cleaning, not the water pressure." Dwell time is what replaces force. Sika instructs a cleaner to "Allow the solution to soak the wall for approximately 15 minutes, but do not allow the cleaning solution to dry on the wall." Sto Corp. gives a slightly longer window for the same chemistry: "Apply the TSP cleaning solution to the wall surface by brush or spray and allow to soak for a period of 15 to 20 minutes", and warns that if bleach "is not allowed sufficient time (about 15 minutes) to sit on the surface and kill the micro-organisms, algae or mildew will re-occur."
That dwell instruction is also a legal instruction once a registered product is in the tank. Under 7 U.S.C. 136j(a)(2)(G) of the Federal Insecticide, Fungicide, and Rodenticide Act, it is unlawful "to use any registered pesticide in a manner inconsistent with its labeling" (read 2026-09-03). EPA defines antimicrobial pesticides as "substances or mixtures of substances used to destroy or suppress the growth of harmful microorganisms such as bacteria, viruses, or fungi on inanimate objects and surfaces", and lists algae under its non-public-health antimicrobial category. A contractor who mixes a registered biocide off-label is not exercising craft judgment, and a property manager is entitled to ask which product is in the tank and to read its label.
Two prohibitions round out the method, both of them published. Sika: "Steam or hot water should not be used to clean EIFS or acrylic finishes over stucco." Sika again, on frequency: "Frequent power-washing should be avoided, it may result in premature deterioration of the LaHabra finish." A soft wash that kills growth buys a longer interval than a rinse that removes color, and the interval, not the pressure, is what protects the finish over a building's life.
What has to be inspected before any water touches a stucco wall?
The inspection is short, and skipping it is what turns a cleaning invoice into a remediation invoice. Five items get walked before the first hose is charged.
- Cracks, sized. Sto Corp. separates repair methods by width, treating hairline cracks as "up to approximately 1/32 inch wide" and moderate cracks as "up to approximately 1/8 inch wide". Anything wider, or any area that sounds hollow behind the finish, comes off the cleaning scope and onto a repair scope.
- Sealant joints. EIMA Technical Bulletin 003 identifies floor lines, expansion joints, dissimilar substrates and window and door abutments among the locations that carry sealant, and those are the locations where a failed joint lets pressurized water behind the cladding.
- Blistered or bubbled finish. Sto Corp. names the cause directly: "A common cause for blistering or bubbling of finish from stucco wall surfaces is water getting behind the finish." Washing a blistered elevation adds water to a wall that already has a leak.
- Grade at the weep screed. The Stucco Manufacturers Association warns that it is "extremely important to keep finish grades, such as planters and concrete walkways, below the weep line". Soil or mulch piled over the screed blocks the drainage path the wall depends on.
- Landscaping and irrigation. Plants below the wall get pre-wetted and rinsed, and the association separately advises that "All sprinkler and irrigation systems must be directed away from all exterior stucco walls", which is a maintenance finding worth reporting even though it sits outside a cleaning scope.
Should cracked stucco be cleaned first or repaired first?
Repair comes first, and the reason is drying rather than appearance. Water forced into an open crack travels behind the coating and into a cavity that has no ventilation, and on an EIFS wall that cavity holds insulation board. Sto Corp.'s guidance is explicit about sequence on a related condition, instructing a repairer to isolate and repair the source of water intrusion before repairing a blister, because otherwise the blister returns.
Cracking on a cement plaster wall is not by itself a defect, and an owner should not be sold a re-stucco on the strength of hairline mapping. The Stucco Manufacturers Association states the position for the industry: "Cracking will occur on most residential homes finished with exterior cement based plaster. Cracking is typical in cement based plaster systems and in most cases is not considered a defect", and adds that "these cracks do not jeopardize the water resistant properties of your stucco system" because the weather resistive barrier sits under the cement. The judgment call is width and pattern, not presence, and the Sto width bands above are the practical dividing line.
Sequencing also protects the finished appearance. A patch applied to a dirty wall matches the dirty wall, and the elevation then washes to two colors. Repair, allow the patch to cure, then clean the whole elevation to one standard.
What is included in a stucco cleaning scope, and what is not?
Scope boundaries are where stucco quotes diverge most, so both sides of the line are written out here. A stucco cleaning scope from Rare Earth Ltd covers the following.
- Identification of the cladding system before pricing, with the pressure ceiling set from the system found rather than from the appearance of the wall.
- A test patch on a small inconspicuous area, which Sika instructs a cleaner to run before any general cleaning.
- Pre-wetting of the elevation from the bottom up, and pre-wetting and rinsing of landscaping below the work area.
- Application of a registered biocide at label dilution, held at the published dwell and not allowed to dry on the wall.
- A low-pressure rinse inside the published ceiling for the system, with a wide fan tip at the published standoff.
- A written note of every crack, failed sealant joint, blister and blocked weep screed found during the walk, handed over whether or not repair is bought from us.
The following sits outside a cleaning scope and is quoted separately, if at all.
- Crack repair, mesh and base coat work, patching, fog coating and recoloring, all of which are finish trades rather than cleaning.
- Sealant joint replacement at windows, doors, floor lines and dissimilar-material transitions.
- Sealer or water-repellent application, which is a separate mobilization on a dry wall and is not appropriate on every system.
- Grading, planter rework or irrigation adjustment where finish grade sits above the weep line.
- Interior moisture investigation, which needs a building envelope consultant rather than a cleaning contractor.
What do we need from you before the crew arrives?
Four things, and all four shorten the visit rather than lengthen it.
- The cladding system, if the building file records it, and the finish manufacturer and color number where one is on record. The Stucco Manufacturers Association advises owners to keep the color number and manufacturer information for future maintenance, and it is the single most useful item in a stucco building file.
- A working exterior water source, or notice that water has to be brought to site.
- Access to every elevation, including gated side yards, courtyards and any area behind a locked amenity fence.
- The site's stormwater constraint, meaning where the drains run and whether the property carries a containment requirement, so the runoff plan is set before mobilization rather than during it.
Where does the wash water go on a commercial stucco elevation?
Wash water from exterior cleaning is not stormwater, and the distinction is regulatory rather than semantic. EPA's NPDES stormwater program treats wash water from exterior cleaning as a non-stormwater discharge under 40 CFR 122.26, which means the water must not enter a municipal separate storm sewer system unless an NPDES permit authorizes it (read 2026-08-31). Wash water off a building elevation routinely carries sediment, detergent, and the biocide residue that did the cleaning. The practical compliance path on a commercial site is containment, because water that never reaches a storm drain needs no permit.
Both manufacturer documents on this page push the same question back to the local jurisdiction rather than answering it nationally. Sto Corp.: "Always check local regulatory requirements for disposal of cleaning solution and waste water." Sika: "Check local regulatory requirements for disposal of wastewater and cleaning solutions." Metro Atlanta jurisdictions differ on this, and a Gwinnett County address, a City of Atlanta address and an unincorporated Fulton address answer to three separate instruments. Runoff control is a scoped line item on a commercial building, which is one of the real differences between a residential stucco wash and a multifamily or commercial one.
Height is the other difference. A commercial or multifamily stucco elevation is worked at height, finished in continuous vertical drops so no lap line dries into the finish, and staged so an occupied building keeps its entrances. A half-cleaned elevation reads worse than an untouched one, which makes sequencing, not chemistry, the hardest part of a large stucco job.
Rare Earth Ltd cleans stucco and EIFS on homes, multifamily properties and commercial buildings across Atlanta, Marietta, Roswell, Stone Mountain and the wider metro. Say the word EIFS when you call if the wall sounds hollow, because the quote is built around the pressure ceiling. Call (678) 748-3578 or schedule a property walk for a written scope.