Drone Soft Washing
Cleaning by water chemistry and dwell time rather than force — the method that lets a drone clean a building envelope without damaging the thing it is cleaning.
Soft washing cleans using low-pressure water and dwell time instead of impact force. It is the correct method for building envelopes because high pressure erodes coatings, stresses sealant joints and drives water past cladding junctions. It is also the only method that works from a drone, because a drone cannot scrub.
Key takeaways
- Chemistry and dwell time, not pressure - that is the whole principle.
- Deionised water below 5 ppm is our standard; no detergents assumed.
- A drone cannot scrub - it has no reaction force to push against, so soft wash is the only viable aerial method.
- High pressure damages envelopes - coatings, silicone, gaskets and cladding joints.
- Pressure washing still has a place - on hard unsealed surfaces, not on building facades.
On this page
The principle: chemistry over force
Conventional pressure washing removes soiling by hitting it hard enough to break its bond with the surface. That works, and it also transfers all of that energy into the surface itself.
Soft washing inverts the approach. Water is applied at low pressure and given time to dissolve and lift the soiling, then rinsed away. The cleaning work is done by the water's properties and its contact time, not by impact. Nothing is transferred into the substrate.
Why drones must soft wash
There is a physical reason aerial cleaning and soft washing go together. A person on a rope or gondola can brace against the building and scrub — they have something to push against. A drone in flight has no reaction force available. Push hard against a surface and the aircraft moves, not the dirt.
That makes mechanical abrasion impossible from a drone, and makes water chemistry the only available cleaning mechanism. Rather than a limitation, it enforces the method that building envelopes should be getting anyway.
The honest consequence. Because it cannot scrub, a drone will not shift deposits that are mechanically bonded to the surface — cement runoff, hardened paint overspray, or mineral staining etched into glass. Those need contact work. We identify them at survey rather than discovering them mid-job.
Why deionised water
Deionised water has had its dissolved mineral content stripped out, typically to below 5 ppm total dissolved solids. Two consequences matter for cleaning:
- It is aggressively "hungry". Pure water seeks to dissolve minerals back into itself, so it lifts mineral and particulate soiling more effectively than tap water at the same pressure.
- It leaves nothing behind. With no dissolved solids, evaporation deposits no residue — so surfaces dry clear with no squeegee, no towelling and no spotting.
That second property is what makes unattended aerial cleaning viable at all. Wash glass with untreated Singapore tap water and no contact drying and it will look worse afterwards.
What soft washing suits
| Surface | Method | Why |
|---|---|---|
| Glass and curtain wall | Soft wash | Protects structural silicone and gaskets |
| ACP and coated cladding | Soft wash | Preserves PVDF and polyester coatings |
| Painted concrete and render | Soft wash | Pressure removes paint along with dirt |
| Solar panels | Soft wash | Protects anti-reflective coating; warranty-safe |
| Metal roofing | Soft wash | Avoids driving water under laps and past fixings |
| Concrete hardstanding, kerbs | Pressure wash | Hard, unsealed, tolerates impact |
Our position on chemicals
Much of the soft washing industry uses sodium hypochlorite and surfactant blends as standard, because chemistry substitutes for the scrubbing that is unavailable. We start from deionised water alone.
Where biological growth is heavy enough that water alone will not clear it, we raise a treatment approach with the building owner explicitly — including what is being applied, and how runoff will be contained. On reservoir-adjacent sites, planted areas and food-handling facilities, that conversation happens before the quote, not after. Chemical use is never assumed into a job.
Frequently asked questions
What is soft washing?
Soft washing cleans a surface using low-pressure water and dwell time rather than force. The cleaning is done by water chemistry and contact time instead of impact pressure, which makes it safe for coatings, sealant joints and delicate substrates.
Is soft washing better than pressure washing for buildings?
For most building envelopes, yes. High pressure erodes coatings, drives water past joints and damages sealant. Soft washing removes the same soiling without those risks. Pressure washing remains appropriate for hard, unsealed surfaces like concrete hardstanding.
Do you use chemicals in soft washing?
Our standard method is deionised water only, with no detergents or biocides. Where heavy biological growth requires it, we discuss a treatment approach with the building owner first, including runoff containment. Chemical use is never assumed.
Why can a drone not scrub a surface?
A drone has no stable reaction force to push against, so it cannot apply mechanical abrasion the way a person with a brush can. All cleaning is achieved through water chemistry, dwell time and controlled flow, which is precisely why the soft wash method suits aerial work.
Not sure which method your building needs?
Send photographs of the worst elevation and we will tell you what will and will not shift it.