How does drone window and facade cleaning work?

A cleaning drone is not a flying window cleaner with a squeegee. It is a drone that moves a spray lance along the glass or facade, while the rest of the work happens on the ground, where the pump, the water, the products and the pilot stay. Below you can read how that works in practice, and when a drone is or is not the right choice.

How does drone window cleaning work, step by step?

The building is surveyed first, a zone on the ground is fenced off, and only then does the drone work along the glass in passes. The result is checked afterwards.

During preparation, the contractor looks at the type of glass and frames, at obstacles such as trees, cables and canopies, and at where the pilot and the equipment can stand. On the day itself, a safety perimeter is set up at the foot of the facade, and nobody enters it while the drone is flying. The drone then works the facade in passes, preferably from top to bottom, so that dirty water does not run over glass that has already been rinsed.

How do water and cleaning product reach the drone?

A drone can only carry a limited weight, so the heavy part stays on the ground. A hose carries water and product from a pump on the ground to the nozzle on the drone, or the drone carries a small reservoir for the product.

The American manufacturer Lucid Bots describes its Sherpa drone as a tethered system that receives water and cleaning solution from the ground and connects to an existing softwash or high-pressure pump. The drone itself runs on batteries, with up to 19 minutes of flight time according to the manufacturer. For windows, Lucid Bots offers an upgrade with an onboard tank that mixes in the product at a variable ratio (Lucid Bots).

Other companies have made different choices. KTV Working Drone, active in Belgium and the Netherlands, describes a non-contact method that combines "filtered water, heat, and moderate pressure", and a patented roof safety system that anchors the drone to the roof of the building (KTV Working Drone). There is no single standard machine, so always ask a contractor which system they use and how it is supplied or secured.

What pressure and what water does a cleaning drone use?

For glass and most facades, the work is done at low pressure with purified water, sometimes with a product suited to the surface. High pressure is technically possible, but calls for more care.

Lucid Bots quotes 300 psi (about 21 bar) for soft washing and up to 4,500 psi (about 310 bar) for heavier work (Lucid Bots). That range matters for your building. Low pressure spares joints, render, seals and the coating of cladding panels; with the softwash principle, a product is left to work and then rinsed off gently. For glass, many contractors use pure water made by reverse osmosis, which contains no dissolved minerals and dries without limescale spots. How that water is made is explained in our article on pure water window cleaning.

What does the pilot do on the ground?

The pilot flies the drone from the ground and keeps it in sight, while a colleague watches the perimeter, the hose and the pump. Nobody works at height.

That is the main difference from traditional work at height. With a cherry picker, rope access or a gondola on a building maintenance unit (BMU), a window cleaner is up against the facade. With a drone, the whole crew stays at ground level. The pilot watches the distance to the glass, the wind and what happens around the perimeter, and stops the flight if someone walks into the fenced-off zone.

Which authorisation does drone cleaning need?

A drone that sprays falls outside the EU open category and into the specific category of Regulation (EU) 2019/947. The operator then needs a declaration under a standard scenario or an operational authorisation from the national aviation authority.

The open category is meant for low-risk flights and explicitly excludes a drone that drops any material (EUR-Lex, Article 4). EASA lists dropping material among the examples of specific-category operations, which need an operational authorisation from the national aviation authority unless they follow a standard scenario or the operator holds a Light UAS Operator Certificate (EASA). In Belgium, the Directorate-General Aviation of the FPS Mobility and Transport lists "dispersing products" as a specific-category example (FPS Mobility and Transport).

Where are the limits of a cleaning drone?

A drone is strong on glass and facades that are hard to reach, but it does not fly in rain or strong wind, and it does not remove heavy crusts the way a pressure washer used at close range can.

Wind and rain are the clearest constraint: above the limits set by the manufacturer and the authorisation, the drone stays on the ground. The surroundings matter too. Trees close to the facade, overhead lines or a pavement too narrow for a perimeter make a flight harder or impossible. Graffiti, thick deposits or cement film often still call for a specialist with suitable equipment. And the inside of the windows remains a job for a window cleaner.

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