Stucco is the one Savannah exterior a pressure washer ruins fastest. Here is how to tell hard-coat from EIFS, the low-pressure soft-wash sequence that actually lifts the green, and why white bloom and open cracks are separate problems cleaning cannot fix.
Stucco is the one Savannah exterior that punishes a pressure washer hardest. It is a porous cement skin, usually only three-quarters of an inch thick, and a narrow tip held too close will cut it, open the hairline cracks it already has, and push water into the wall cavity behind it. The method that works on stucco is chemistry at low pressure: identify whether you have traditional hard-coat stucco or synthetic EIFS, pre-wet the wall and the plants under it, apply a dilute bleach-and-surfactant mix through a soft-wash setup, let it dwell while the green fades, then rinse from top to bottom with a wide fan at garden-hose force. If you remember one number from this page, remember this one: nothing above roughly 500 PSI should ever touch a stucco wall, and most of the cleaning happens with the pressure off entirely.
Savannah has both kinds, and they fail in completely different ways, so this is not an academic distinction. Traditional hard-coat stucco is portland cement applied in coats over lath or directly over masonry. Much of the Historic District is this: stucco spread over brick, scored and painted, on Federal and Regency-era buildings where the mason wanted the look of dressed stone at a fraction of the cost. It is heavy, hard, and rings solid when you tap it. Synthetic stucco, properly called EIFS, is a much newer system: a foam insulation board fastened to sheathing, wrapped in a thin fiberglass-reinforced base coat and a flexible acrylic finish. It shows up on newer construction out toward the islands and the suburbs. Tap it and it sounds hollow, because it is.
The reason it matters is water. Hard-coat stucco over brick can get wet and dry out again; the masonry behind it tolerates moisture. EIFS is a barrier system, and if water gets behind the foam through a crack, a failed sealant joint, or a pressure washer forced into a seam, it has nowhere to go and no way to dry. That is how EIFS rots sheathing from the inside while the outside still looks fine. On EIFS you clean gently or you do not clean at all, and you never aim a stream at a joint, a penetration, or the terminating edge above grade.
What darkens a wall here is biological, not dirt, and that is why scrubbing accomplishes so little. Three local conditions stack up. The first is humidity: coastal Georgia holds moisture in the air most of the year, and a shaded wall in Savannah can stay damp for the better part of a morning even without rain. The second is shade. The live oak canopy that makes the squares beautiful also means many walls never see direct sun, and a wall that never dries is a wall that grows things. The third is that stucco is porous by design, with a texture full of tiny pockets that hold moisture and give spores somewhere to sit.
What grows in those conditions is mostly algae, mildew, and in the wettest north-facing spots, moss. Green tint is algae. Grey-to-black speckling that starts near grade or under a drip line is usually mildew. Add river salt, pollen in spring, and the fine grit that traffic throws onto street-facing walls, and you get the dull, mottled look that homeowners read as "the stucco is stained" when the pigment underneath is generally fine.
On stucco, the solution does the cleaning and the hose only carries the residue away. Sequence matters far more than equipment here.
Start by soaking every plant, bed, and patch of lawn within reach of the wall and the runoff path, then soak them a second time once you are finished. Skipping that soak is behind most of the collateral damage on residential jobs. Next, pre-wet the stucco itself with plain water. A dry porous wall drinks the solution straight in, which both wastes it and leaves streaks; a damp wall holds it on the surface where the work happens.
Mix a dilute sodium hypochlorite solution with a surfactant to help it cling. Dilute means dilute: a low single-digit percentage at the wall is plenty for organic growth, and stronger is not faster, it is just harder on plants and painted trim. Apply it low to high through a soft-wash nozzle or a pump sprayer at garden-hose pressure. Working upward prevents the clean streaks that appear when solution runs down over dry material.
Then wait. Ten to fifteen minutes is normal, and you should be able to watch the green pale as it works. If it has not moved at all, the answer is a second application, not a pressure washer. Keep the wall damp through the dwell; letting the solution dry on the surface is what leaves the ghost marks people blame on the chemical.
Rinse top to bottom with a wide fan, forty degrees or wider, from at least a foot and a half back, using the lowest pressure that carries the residue away. Then re-soak the plants. Some discoloration will keep fading over the following week as sun and rain finish the job.
The damage is rarely dramatic on the first pass, which is what makes it so common. A zero-degree or fifteen-degree tip held close enough will erode the finish coat and leave a lighter, rougher patch where the aggregate is exposed. Wave the wand and you get a series of those, visible in raking afternoon light forever afterward even though they looked fine while wet.
The worse problem is invisible. Stucco develops hairline cracks as a matter of course, from ordinary settlement and thermal movement, and most of them are harmless because surface tension keeps rain out. A pressure washer defeats surface tension. Water driven into a crack, up under a weep screed, or into the gap around a window flange ends up behind the wall, and on a wood-framed house the first sign is often a stain on drywall months later. On EIFS, as above, the water has no exit at all.
If part of the wall has a white powdery bloom, particularly near grade or under a persistently damp spot, that is efflorescence, not mildew, and bleach will do nothing to it. It is mineral salt: water moves through the masonry, dissolves salts on the way, reaches the surface, evaporates, and leaves the salt behind as a crust. Coastal ground moisture and irrigation spray hitting the base of a wall make it common here.
Light efflorescence often comes off dry with a stiff brush, which is worth trying first because it costs nothing. Heavier deposits need a masonry-safe efflorescence remover, applied to a pre-wet wall and neutralized afterward. Muriatic acid straight from the bottle is the wrong tool; it burns the finish, can etch the surrounding stucco, and will strip color from painted work.
The important point is that efflorescence is a symptom. It means water is moving through the wall from somewhere: a downspout dumping at the foundation, irrigation heads pointed at the house, a failed sealant joint, grade that slopes the wrong way. Clean it off and leave the source alone and it returns, usually within a season.
Walk the wall before you wet it. Hairline cracks, the kind you can barely catch a fingernail in, are normal and can be cleaned around without much thought. Cracks wide enough to see daylight through, cracks that step diagonally from a window corner, soft or spongy spots, bulges, and areas that sound hollow on a house that is otherwise hard-coat all mean the wall needs repair before it needs washing. Cleaning those is just an efficient way to inject water into the exact places it should not go.
Older painted stucco in the Historic District deserves an extra minute. Paint that is already chalking or lifting at the edges will come off with the algae, and on a contributing structure in a designated district, repainting is not always a free choice about color and product. If the finish is failing, get the repair and repaint sequence settled first, then clean.
Pricing varies with height, access, how much of the wall is stucco versus brick or siding, and how much landscaping has to be protected, so treat any number here as a starting point rather than a quote. For a single-story Savannah home with straightforward access, a stucco soft wash generally lands in the low-to-mid hundreds. Two stories, tight side-yard access, heavy plantings, or a historic property where trim and paint need careful handling push it up from there. Efflorescence treatment is usually priced separately, because it is a different chemical process and often a slower one.
What should make you cautious is a quote that is far below the others, especially from someone describing the job as pressure washing rather than soft washing. On stucco, the cheap fast version and the wall-damaging version tend to be the same version.
Most Savannah stucco benefits from a wash every eighteen months to two years. Shaded north-facing walls, anything under heavy oak canopy, and walls close to standing water or irrigation may need it annually. Sunny, well-drained elevations can go longer.
You can stretch the interval with maintenance that has nothing to do with washing. Trim vegetation back off the wall so air moves and the surface dries. Redirect irrigation heads that are spraying stucco daily. Keep gutters and downspouts clear and discharging away from the foundation, since most of the worst staining on any Savannah house starts at a spot where water repeatedly runs where it should not.
A ground-floor wall you can reach comfortably from the ground, with a pump sprayer and a garden hose, is a reasonable weekend job if you pre-wet the plants and keep the pressure off. Bring in a professional when the work is above the first floor, when the system is EIFS, when the wall is painted and the paint is aged, when efflorescence keeps returning, or when you have found cracks you are not sure about. Ladder work with a sprayer in one hand is where most homeowner stucco jobs go wrong, and the wall is the least valuable thing at risk in that scenario.
If you want the wall handled without the guesswork, our Savannah house washing service covers stucco, brick, tabby, and siding with the same low-pressure approach described here.
The short version: identify the system, protect the plants, let dilute chemistry and patience do the work, keep the pressure low and the fan wide, and treat white bloom and open cracks as separate problems that cleaning cannot solve. Do that and a Savannah stucco wall comes back looking right without paying for it later in water damage.
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