A skylight cleaning robot does not cause leaks by itself, but 400-800 L of rinse water per roof per visit will find any gasket or sealant joint that was already failing. A 15-minute frame inspection before the first run prevents most leak callouts.
Here is the uncomfortable part. The robot gets blamed. A property manager sees water below a skylight the week after cleaning and assumes the machine did it. Usually the seal was cracked for two summers and the robot simply delivered the water that exposed it.
What in a skylight frame actually fails?
- Compression gaskets that have gone hard and lost rebound after 8-10 years.
- Butt joints in structural sealant with a hairline split.
- Weep holes blocked by debris and dried algae.
- Drainage channels that no longer shed water to the outside.
None of these are robot problems. All of them get worse once regular wet cleaning starts.
Does suction pull water into joints?
Suction pads seal against glass, not against frames, so most negative pressure stays on the pane. The bigger effect is the squeegee pushing a wave of water toward the perimeter, straight into the weakest joint. On a framed skylight with a 6 mm gasket gap, that wave is where leaks start.
The mitigation is boring and effective: run the outer lane with reduced flow and lift the squeegee at the frame line, then do the perimeter by hand with a controlled cloth. Machine time drops maybe 10% on a small roof and leak risk drops a lot.
How do you inspect a skylight before robot cleaning?
| Check | Pass | Fail action |
|---|---|---|
| Gasket rebound | Springs back in <1 s | Reseal or replace before cleaning |
| Sealant joints | Continuous, no cracks | Rake and re-seal, cure 24 h |
| Weep holes | Clear, water drains | Clean, then retest flood |
| Drainage channel | Water exits to exterior | Repair before any wet run |
Do a water test on one bay with a hose before running the machine across the whole roof. It costs 20 minutes and tells you what a full run would have told you after the damage. Related reading: robot runtime and charging economics.
Who should skip robot cleaning on ageing skylights?
If the roof is past 15 years with unknown seal history, or if there is already an active leak note, do not start a wet robot program. Fix the envelope first. A robot is a maintenance tool for sound skylights, not a diagnostic for failing ones. Lingdu Intelligence machines like the Lingkong K3 and Lingyun Y3 run fine on inspected frames; they will not save a roof that is already letting water in.
Key Takeaways
- Robots expose pre-existing seal failures; they rarely create them.
- A single visit can put 400-800 L of water across a roof.
- Squeegee water waves at the perimeter are the real leak trigger.
- Inspect gaskets, joints, weep holes and drainage before the first run.
- On roofs over 15 years or with active leaks, fix seals before cleaning.
Does suction stress the glass itself?
Pad pressure is spread over the pad area, so the load per square centimetre stays low, typically well under what the glass already carries from wind. The risk is not the pane but the frame and the point where the pane bears on its setting blocks. On a poorly bedded unit, repeated downforce can work a pane loose over months.
Watch for a pane that rocks when a person leans on it. That is a bedding problem, and a robot will find it repeatedly.
How should you document a pre-clean inspection?
Photograph every bay, note the gasket condition and any existing damp staining, and date the file. When a leak appears later, this record is the difference between a warranty argument and a clear picture of what existed before. It takes ten minutes and it protects both the cleaner and the client.
- Photo per bay, wide and close.
- Note gasket age if known.
- Log any current damp marks or paint blistering.
- Record the water test result per bay.
Do internal linings show leaks before the roof does?
Often yes. A ceiling tile stain or a streak on an internal column appears days after water enters. Before a robot program starts, photograph the interior below each skylight too. That baseline tells you whether a later stain is new or was always there, which is the single most common dispute in skylight cleaning.
What does a leak actually cost compared with prevention?
A single commercial leak callout, including internal repairs and lost trading time, can run into thousands. A pre-clean frame inspection costs a couple of hours. The arithmetic is not close. Firms that skip the inspection are not saving money, they are delaying a bill and letting it grow.
The same logic applies to gutter clearing before a wet season. It is dull work, it is not the robot, and it prevents the leak that the robot would otherwise get blamed for.
How often should frames be re-checked?
Once a year for a sound roof, and before every visit on a roof past ten years old. Sealant ages faster on the sunny side of a building, so the two ends of the same skylight can be in different condition. Check the hot faces first; that is where the first crack will be.
Who is responsible if a leak appears?
Sort this out in the contract, not after the fact. State that the cleaner documents pre-existing conditions and is not liable for latent defects in the glazing or frame. State too that the client will fix any known failure before wet cleaning starts. Clear wording here prevents the argument that the robot caused a leak that the sealant had been inviting for years.