Exterior-cleaning pressure should be chosen for the substrate, finish condition, contaminant, and manufacturer instructions. Painted, coated, stucco, EIFS, historic masonry, and roofing surfaces can be damaged by an indiscriminate high-pressure method, so the lowest effective pressure and a test patch are the responsible starting point.
The 60-second definition
Soft washing uses a compatible cleaning solution, controlled dwell time, and low-pressure application and rinsing instead of relying mainly on water force. The exact chemistry, concentration, pressure, and runoff controls must match the contaminant and surface.
Pressure washing cleans mainly with mechanical force. It may be appropriate for sound hard surfaces when pressure, nozzle, distance, and runoff are controlled. Building height does not determine the method; the substrate and its condition do.
Why it matters for your building
Some black streaking is biological growth, not ordinary dirt. Algae, mildew, moss, and lichen require different treatment from atmospheric soil or oxidation. High pressure alone can damage delicate finishes without addressing the contaminant. A compatible cleaning solution, test patch, controlled dwell time, and low-pressure rinse are the safer starting point for many coated surfaces. Recurrence varies with climate, shade, moisture, and surface condition; there is no universal result duration.
Delicate surfaces need a project-specific method. EIFS and stucco can be damaged or forced full of water by excessive pressure. Painted and coated surfaces can strip or streak, and abrasive roof cleaning can loosen granules. Manufacturer instructions, a test patch, and the mildest successful method should control the plan.
Spray and runoff need a control plan. A responsible scope specifies the product, dilution, application method, dwell time, rinse or neutralization procedure, adjacent-material protection, landscaping protection, and wastewater controls. Wind and building geometry can change whether that plan is workable on a given day.
Where the drone comes in
Traditional soft washing still has an access problem: the applicator may need a lift, rope system, scaffold, or roof-access plan. Those methods introduce fall-protection and access requirements in addition to the chemistry and runoff controls that every method still needs.
A drone-supported method can move the applicator off some elevated surfaces when the substrate, airspace, weather, standoff distance, spray drift, ground controls, and equipment limits allow it. That feasibility decision belongs in the project plan; a drone is an access option, not permission to skip surface testing or site controls.
Quick reference: which wash does your surface need?
| Surface | Method |
|---|---|
| EIFS / stucco / Dryvit | Follow the finish manufacturer; test compatible low-pressure chemistry first |
| Painted or coated facades | Follow the coating specification; test for color, adhesion, and streaking |
| Roof systems | Use only the roof manufacturer’s approved products, pressure, and procedure |
| Brick and masonry | Diagnose the masonry and stain; start with the gentlest effective tested method |
| Concrete flatwork and decks | Confirm concrete condition, coating or sealer, pressure, drainage, and runoff controls |
| Metal panel | Follow panel and coating guidance; test chemistry, pressure, and rinse behavior |
If a contractor quotes one method for the whole property, ask how it accounts for each substrate, coating, contaminant, opening, adjacent material, and drainage path. A credible answer starts with manufacturer guidance and test patches, then documents where the method changes.
Questions this answers
What is soft washing?
Soft washing uses a compatible cleaning solution, controlled dwell time, and low-pressure application and rinsing instead of relying mainly on water force. The exact chemistry and pressure must match the contaminant and surface.
Is soft washing safe for EIFS and stucco?
It can be appropriate when the finish manufacturer allows the chemistry and pressure, a test patch succeeds, and openings and adjacent materials are protected. EIFS condition and coating specifications must be checked first.
How long do soft-wash results last?
There is no universal interval. Recurrence depends on climate, shade, moisture, surface condition, and the contaminant. Inspect the building periodically and follow the cladding or coating manufacturer's maintenance guidance.
Sources and standards
- Recommendations for Periodic Cleaning of Dryvit Finishes and CoatingsDryvit Systems
- Cleaning Historic Masonry: Removal of Soiling, Stains, and Biological GrowthU.S. General Services Administration